4,253 results on '"Dication"'
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2. Ion valence-gated photochromism of an aza-crowned diarylethene.
- Author
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Takeguchi, Ayaka, Kikuchi, Azusa, Ueno, Kazuhide, Ishihara, Shinji, Nitta, Aki, Nakagawa, Tetsuya, Ubukata, Takashi, and Yokoyama, Yasushi
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ALKALI metals , *ALKALINE earth metals , *INTRAMOLECULAR charge transfer , *PHOTOCHROMISM , *DIARYLETHENE , *IONS , *MONOVALENT cations - Abstract
A non-photochromic diarylethene 2o with an N-phenylaza-15-crown-5 was synthesized. When the nitrogen atom in the aza-crown ring was protonated, it became photochromic due to the prevention of a twisted intramolecular charge transfer (TICT). Although addition of a monovalent metal cation (Li+, Na+, K+, Rb+, Cs+, Cu+, Ag+) in acetonitrile could not stop the TICT so that it was not photochromic, the addition of a multivalent metal cation (Mg2+, Ca2+, Sr2+, Ba2+, Fe2+, Ni2+, Al3+, Sb5+) changed 2o to be photochromic due to the strong attraction of the lone pair on the nitrogen atom. In the presence of excess Cu2+, 2o was oxidized to be EPR-detectable 2o·+, which was thermally unstable as well as inert towards visible-light irradiation. However, 2o·+ was further oxidized to be fairly stable 2o2+ by the irradiation of 365-nm light in the presence of Cu2+. ESI–MS measurements strongly suggested the generation of 2o·+ by mixing 2o with Cu(ClO4)2 in acetonitrile, and the transformation of 2o·+ to 2o2+ by successive 365-nm light irradiation. Fe3+ similarly worked as the oxidant, but the two-step oxidation of 2o to 2o2+ occurred more easily. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Synthesis and Characterization of a Stable Nickelocenium Dication Salt.
- Author
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Rall, Jan M., Lapersonne, Max, Schorpp, Marcel, and Krossing, Ingo
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SALT , *X-ray diffraction , *CHEMICAL bond lengths , *CYCLIC voltammetry , *SINGLE crystals - Abstract
We report the synthesis and characterization of the nickelocenium cations [NiCp2]⋅+ and [NiCp2]2+ as their [F‐{Al(ORF)3}2]− (Cp = C5H5; RF=C(CF3)3) salts. Diamagnetic [NiCp2]2+ represents the first example for the isolation of an unsubstituted parent metallocene dication. Both salts were generated by reacting neutral NiCp2 with [NO]+[F‐{Al(ORF)3}2]− in 1,2,3,4‐tetrafluorobenzene (4FB). The salts were characterized by single crystal X‐ray diffraction (XRD), indicating shorter metal‐ligand bond lengths for the higher charged salt. Powder XRD shows the salts to be phase pure, cyclic voltammetry in 4FB gave quasi reversible redox waves at −0.44 (0→1) and +1.17 V (1→2) vs Fc/Fc+. The 1H NMR of [NiCp2]2+ is a singlet at 8.6 ppm, whereas paramagnetic [NiCp2]⋅+ is significantly shifted upfield to −103.1 ppm. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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4. Natural bond orbital analysis of dication magnesium complexes [Mg(H2O)6]2+ and [[Mg(H2O)6](H2O)n]2+; n=1-4
- Author
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Ganesh Prasad Tiwari, Santosh Adhikari, Hari Prasad Lamichhane, and Dinesh Kumar Chaudhary
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dft ,b3lyp ,delocalization ,nbo ,ligand ,dication ,Biology (General) ,QH301-705.5 ,Biotechnology ,TP248.13-248.65 - Abstract
The metal ion is ubiquitous in the human body and is essential to biochemical reactions. The study of the metal ion complexes and their charge transfer nature will be fruitful for drug design and may be beneficial for the extension of the field. In this regard, investigations into charge transport properties from ligands to metal ion complexes and their stability are crucial in the medical field. In this work, the DFT technique has been applied to analyze the delocalization of electrons from the water ligands to a core metal ion. At the B3LYP level of approximation, natural bond orbital (NBO) analysis was performed for the first five distinct complexes [Mg(H2O)6]2+ and [[Mg(H2O)6](H2O)n]2+; n = 1-4. All these complexes were optimized and examined with the higher basis set 6-311++G(d, p). In the complex [Mg(H2O)6]2+, the amount of natural charge transport from ligands towards the metal ion was 0.179e, and the greatest stabilization energy was observed to be 22.67 kcal/mol. The donation of the p orbitals in the hybrid orbitals was increased while approaching the oxygen atoms of H2O ligands in the 1st coordination sphere with the magnesium ions. The presence of water ligands within the 2nd coordination sphere increased natural charge transfer and decreased the stabilizing energy of the complexes. This may be due to the ligand-metal interactions.
- Published
- 2023
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5. Molecular Weight-Dependent Oxidation and Optoelectronic Properties of Defect-Free Macrocyclic Poly(3-hexylthiophene).
- Author
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Sato, Ryohei, Utagawa, Atsuo, Fushimi, Koji, Li, Feng, Isono, Takuya, Tajima, Kenji, Satoh, Toshifumi, Sato, Shin-ichiro, Hirata, Hiroshi, Kikkawa, Yoshihiro, and Yamamoto, Takuya
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ELECTRON paramagnetic resonance spectroscopy , *DEGREE of polymerization , *CYCLIC voltammetry , *OXIDATION , *POLARONS , *CONJUGATED polymers , *POLYMERIZATION - Abstract
The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Directed Synthesis and Chemistry of Unsymmetric Dicationic Diboranes and Their Use in Frustrated Lewis Pair‐like Chemistry.
- Author
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Kistner, Lucas, Kowatsch, Dario, Marz, Andreas, Kaifer, Elisabeth, and Himmel, Hans‐Jörg
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LEWIS pairs (Chemistry) , *DIBORANE , *LEWIS acids , *PYRIDINE - Abstract
The chemistry of dicationic diboranes with two BII atoms that are engaged in direct B−B bonding is by enlarge unexplored, although these molecules have intriguing properties due to their combined Lewis acidic and electron‐donor properties. Unsymmetric dicationic diboranes are extremely rare, but especially attractive due to their polarized B−B bond. In this work we report the directed synthesis of several stable unsymmetric dicationic diboranes by reaction between the electron‐rich ditriflato‐diborane B2(hpp)2(OTf)2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate) and phosphino‐pyridines, establishing B−N and B−P bonds with the diborane concomitant with triflate elimination. In the case of 2‐((ditertbutylphosphino)methyl)pyridine, the B−N bond is formed instantly, but the B−P bond formation requires (due to steric constraints) several days at ambient conditions for completion, creating an intermediate that could be used for frustrated Lewis pair (FLP)‐like chemistry. Here we test its reaction with an aldehyde, and propose a new type of FLP‐like chemistry. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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7. Dianion and Dication of Tetracyclopentatetraphenylene as Decoupled Annulene‐within‐an‐Annulene Models.
- Author
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Miyoshi, Hirokazu, Sugiura, Ryosuke, Kishi, Ryohei, Spisak, Sarah N., Wei, Zheng, Muranaka, Atsuya, Uchiyama, Masanobu, Kobayashi, Nagao, Chatterjee, Shreyam, Ie, Yutaka, Hisaki, Ichiro, Petrukhina, Marina A., Nishinaga, Tohru, Nakano, Masayoshi, and Tobe, Yoshito
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DIANIONS , *ELECTRON configuration , *ALKALI metals , *ANTIMONY - Abstract
The dianion and dication of tetramesityl‐substituted tetracyclopentatetraphenylene, a circulene consisting of alternating five‐ and six‐membered rings, have been generated by reduction with alkali metals and oxidation with antimony(V) halides, respectively. They are theoretically predicted to adopt double annulenoid structures called annulene‐within‐an‐annulene models in which the outer and inner conjugation circuits are significantly decoupled. The theoretical structures were experimentally proven by X‐ray crystallographic analyses and the electronic configurations were supported by MCD spectra. Based on the 13C NMR chemical shifts, negative and positive charges are shown to be located mainly at the outer periphery, indicating that the dianion and dication have delocalized 22‐π and 18‐π electron outer perimeters, respectively, and 8‐π electron structure at the inner ring. Notably, the dianion has an open‐shell character, whereas the dication has a closed‐shell ground state. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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8. One‐ and Two‐Electron Transfer Oxidation of 1,4‐Disilabenzene with Formation of Stable Radical Cations and Dications.
- Author
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Chen, Yilin, Chen, Zhikang, Jiang, Liuyin, Li, Jiancheng, Zhao, Yiling, Zhu, Hongping, and Roesky, Herbert W.
- Subjects
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RADICAL cations , *ELECTRON paramagnetic resonance spectroscopy , *X-ray crystallography , *NUCLEAR magnetic resonance spectroscopy , *ULTRAVIOLET-visible spectroscopy , *ELEMENTAL analysis , *RADICAL anions - Abstract
Electron‐transferable oxidants such as B(C6F5)3/nBuLi, B(C6F5)3/LiB(C6F5)4, B(C6F5)3/LiHBEt3, Al(C6F5)3/(o‐RC6H4)AlH2 (R=N(CMe2CH2)2CH2), B(C6F5)3/AlEt3, Al(C6F5)3, Al(C6F5)3/nBuLi, Al(C6F5)3/AlMe3, (CuC6F5)4, and Ag2SO4, respectively were employed for reactions with (L)2Si2C4(SiMe3)2(C2SiMe3)2 (L=PhC(NtBu)2, 1). The stable radical cation [1]+. was formed and paired with the anions [nBuB(C6F5)3]− (in 2), [B(C6F5)4]− (in 3), [HB(C6F5)3]− (in 4), [EtB(C6F5)3]− (in 5), {[(C6F5)3Al]2(μ‐F)]− (in 6), [nBuAl(C6F5)3]− (in 7), and [Cu(C6F5)2]− (in 8), respectively. The stable dication [1]2+ was also generated with the anions [EtB(C6F5)3]− (9) and [MeAl(C6F5)3]− (10), respectively. In addition, the neutral compound [(L)2Si2C4(SiMe3)2(C2SiMe3)2][μ‐O2S(O)2] (11) was obtained. Compounds 2–11 are characterized by UV‐vis absorption spectroscopy, X‐ray crystallography, and elemental analysis. Compounds 2–8 are analyzed by EPR spectroscopy and compounds 9–11 by NMR spectroscopy. The structure features are discussed on the central Si2C4‐rings of 1, [1]+. [1]2+, and 11, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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9. Observation of CO2++ dication in the dayside Martian upper atmosphere
- Author
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Hao Gu, Jun Cui, DanDan Niu, LongKang Dai, JianPing Huang, XiaoShu Wu, YongQiang Hao, and Yong Wei
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maven ,martian ionosphere ,dication ,Science ,Geophysics. Cosmic physics ,QC801-809 ,Environmental sciences ,GE1-350 - Abstract
Doubly charged positive ions (dications) are an important component of planetary ionospheres because of the large energy required for their formation. Observations of these ions are exceptionally difficult due to their low abundances; until now, only atomic dications have been detected. The Neutral Gas and Ion Mass Spectrometer (NGIMS) measurements made on board the recent Mars Atmosphere and Volatile Evolution mission provide the first opportunity for decisive detection of molecular dications, CO2++ in this case, in a planetary upper atmosphere. The NGIMS data reveal a dayside averaged CO2++ distribution declining steadily from 5.6 cm−3 at 160 km to below 1 cm−3 above 200 km. The dominant CO2++ production mechanisms are double photoionization of CO2 below 190 km and single photoionization of CO2+ at higher altitudes; CO2++ destruction is dominated by natural dissociation, but reactions with atmospheric CO2 and O become important below 160 km. Simplified photochemical model calculations are carried out and reasonably reproduce the data at low altitudes within a factor of 2 but underestimate the data at high altitudes by a factor of 4. Finally, we report a much stronger solar control of the CO2++ density than of the CO2+ density .
- Published
- 2020
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10. Preparation, Structure Determination, and Electrochemical Properties of 4,5‐Dialkylbenzo[1,2‐d:4,5‐d']bis[1,2,3]triselenoles and Their Singlet and Triplet‐State Dications.
- Author
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Kimura, Takeshi, Nakahodo, Tsukasa, Suzuki, Eiichi, Nakanishi, Yoshiki, Misaki, Yohji, and Ogawa, Satoshi
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SUPERCONDUCTING quantum interference devices , *DENSITY functional theory , *NUCLEAR magnetic resonance spectroscopy , *MAGNETIC susceptibility , *OXIDATION - Abstract
4,8‐Dialkylbenzo[1,2‐d:4,5‐d']bis[1,2,3]triselenoles [alkyl=Et, Bu, and Oc (C8H17)] were first prepared and treated with concentrated sulfuric acid‐d2 to generate benzobistriselenole dications, which were determined by NMR spectroscopy. The oxidation of dioctylbenzobistriselenole with three equivalents of single‐electron oxidizing reagent (NOSbF6) produced the corresponding dication.2SbF6−, and the salt was isolated into a stable form. The ESR spectra of the dications measured in concentrated sulfuric acid in the range of room temperature and −196 °C were observed as split peaks similar to that of solid state dication.2SbF6−. Magnetic susceptibility of the dication.2SbF6− was determined by a superconducting quantum interference device (SQUID) magnetometer, which showed the salt is diamagnetic. The optimized structures and the total energy of the singlet‐ and triplet‐state benzobistriselenole dications were calculated using the density functional theory (DFT) method at the B3LYP6‐311G**(d,p) level. The results revealed that the structures of the singlet‐ and triplet‐state dications calculated have a completely planar forms and the triplet‐state dication is slightly more stable than the singlet‐state one in acetonitrile using a polarizable continuum model (PCM). [ABSTRACT FROM AUTHOR]
- Published
- 2021
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11. Comparison of three related imidazolium ionic liquids and their CS2 solutions.
- Author
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Lynden-Bell, R. M.
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IONIC liquids , *ALKYL group , *GROUP rings , *CESIUM compounds , *COMPUTER simulation , *LIQUIDS - Abstract
The aim of this paper is to give examples showing how computer simulation can be used to obtain insight into the behaviour of ionic liquids. Three related ionic liquids with cations containing imidazolium rings and alkyl groups were studied, namely the monocationic liquids 1-butyl 3-methyl imidazolium triflimide ([C 4 H 9 CH 3 im][(CF 3 SO 2 ) 2 N]), 1-octyl 3-methyl imidazolium triflimide ([C 8 H 1 7 CH 3 im][ (CF 3 SO 2 ) 2 N]) and the dicationic liquid ([C 8 H 1 6 (CH 3 im) 2 ][(CF 3 SO 2 ) 2 N] 2 ). We find that the local structure of the liquids is similar in the dicationic and the C 4 liquid but nanophase separation occurs in the C 8 monocationic liquid, making the latter the odd one out for local structure. In contrast, for dynamical properties it is the liquid containing the dication which differs from the other two liquids showing that the dynamical properties are not necessarily correlated with equilibrium structure. The results of simulations of a probe molecule, CS 2 , in the three liquids are compared. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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12. Management of systemic lupus erythematosus during pregnancy: challenges and solutions
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Knight CL and Nelson-Piercy C
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systemic lupus erythematosus ,conception counselling ,dication ,nagement of pregnancy ,pregnancy complications ,neonatal lupus ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Caroline L Knight, Catherine Nelson-Piercy Division of Women’s Health, Women’s Health Academic Centre, King’s College London and King’s Health Partners, St Thomas’ Hospital, London, UK Abstract: Systemic lupus erythematosus (SLE) is a chronic, multisystem autoimmune disease predominantly affecting women, particularly those of childbearing age. SLE provides challenges in the prepregnancy, antenatal, intrapartum, and postpartum periods for these women, and for the medical, obstetric, and midwifery teams who provide their care. As with many medical conditions in pregnancy, the best maternal and fetal–neonatal outcomes are obtained with a planned pregnancy and a cohesive multidisciplinary approach. Effective prepregnancy risk assessment and counseling includes exploration of factors for poor pregnancy outcome, discussion of risks, and appropriate planning for pregnancy, with consideration of discussion of relative contraindications to pregnancy. In pregnancy, early referral for hospital-coordinated care, involvement of obstetricians and rheumatologists (and other specialists as required), an individual management plan, regular reviews, and early recognition of flares and complications are all important. Women are at risk of lupus flares, worsening renal impairment, onset of or worsening hypertension, preeclampsia, and/or venous thromboembolism, and miscarriage, intrauterine growth restriction, preterm delivery, and/or neonatal lupus syndrome (congenital heart block or neonatal lupus erythematosus). A cesarean section may be required in certain obstetric contexts (such as urgent preterm delivery for maternal and/or fetal well-being), but vaginal birth should be the aim for the majority of women. Postnatally, an ongoing individual management plan remains important, with neonatal management where necessary and rheumatology follow-up. This article explores the challenges at each stage of pregnancy, discusses the effect of SLE on pregnancy and vice versa, and reviews antirheumatic medications with the latest guidance about their use and safety in pregnancy. Such information is required to effectively and safely manage each stage of pregnancy in women with SLE. Keywords: systemic lupus erythematosus, preconception counseling, medication, management of pregnancy, pregnancy complications, neonatal lupus
- Published
- 2017
13. Tracing the Antibacterial Performance of Bis-Imidazolium-based Ionic Liquid Derivatives.
- Author
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Hassanpour M, Torabi SM, Afshar D, Kowsari MH, Meratan AA, and Nikfarjam N
- Subjects
- Escherichia coli, Anti-Bacterial Agents pharmacology, Anti-Bacterial Agents chemistry, Structure-Activity Relationship, Cations chemistry, Ionic Liquids pharmacology, Ionic Liquids chemistry
- Abstract
Ionic liquid (IL) cationic species have recently captivated the attention of pharmacists, biochemists, and biomedical scientists as promising antibacterial agents to deal with the multidrug resistance bacteria crisis. The structure and functional groups of ILs influence their physiochemical properties and biological activities. However, a comprehensive study is required to fully understand the details of the antibacterial activity of ILs carrying various functional groups. Herein, dicationic ILs (DCILs) are reported based on imidazolium rings as efficient antibacterial agents. The DCILs carried various functionalities such as 2-hydroxybutyl (DCIL-1), 2-hydroxy-3-isopropoxypropyl (DCIL-2), 2-hydroxy-3-(methacryloyloxy)propyl (DCIL-3), 2-hydroxy-2-phenylethyl (DCIL-4), and 2-hydroxy-3-phenoxypropyl (DCIL-5). The structure-antibacterial activity relationships of the DCILs against Gram-positive ( Staphylococcus aureus ) and Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa ) were comprehensively studied through antibacterial tests, morphology analysis, and adhesion tests. The experimental assays revealed an antibacterial efficacy order of DCIL-5 > DCIL-1 > DCIL-4 > DCIL-2 > DCIL-3. The all-atom molecular dynamics (MD) simulation showed a deep permeation of the hydrophobic -OPh functional group of DCIL-5 through the E. coli membrane model in agreement with the experimental observations. Current findings assist scientists in designing new task-specific DCILs for effective interactions with biological membranes for different applications.
- Published
- 2024
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14. Enhanced host-guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges.
- Author
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Kayahara E, Mizuhata Y, and Yamago S
- Abstract
A dication of [5]cycloparaphenylene ([5]CPP
2+ ) was selectively encapsulated by neutral [10]CPP to form the shortest double-layer carbon nanotube, [10]CPP⊃[5]CPP2+ . While the same host-guest complex consisted of neutral CPPs, [10]CPP⊃[5]CPP, was already reported, the cationic complex showed an about 20 times higher association constant in (CDCl2 )2 at 25 °C (103 mol L-1 ). Electrochemical and photophysical analyses and theoretical calculations suggested the partial electron transfer from [10]CPP to [5]CPP2+ in the complex, and this charge-transfer (CT) interaction is most likely the origin of the higher association constant of the dicationic complex than the neutral one., (Copyright © 2024, Kayahara et al.)- Published
- 2024
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15. Bis‐copper(II) Complex of Triply‐linked Corrole Dimer and Its Dication.
- Author
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Ooi, Shota, Tanaka, Takayuki, Ikeue, Takahisa, Yamasumi, Kazuhisa, Ueta, Kento, Shimizu, Daiki, Ishida, Masatoshi, Furuta, Hiroyuki, and Osuka, Atsuhiro
- Subjects
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COPPER chlorides , *SPIN-spin interactions , *COPPER ions , *LIGANDS (Chemistry) , *SQUIDS , *METALS - Abstract
Copper complexes of corroles have recently been a subject of keen interest due to their ligand non‐innocent character and unique redox properties. Here we investigated bis‐copper complex of a triply‐linked corrole dimer that serves as a pair of divalent metal ligands but can be reduced to a pair of trivalent metal ligands. Reaction of triply‐linked corrole dimer 2 with Cu(acac)2 (acac=acetylacetonate) gave bis‐copper(II) complex 2Cu as a highly planar molecule with a mean‐plane deviation value of 0.020 Å, where the two copper ions were revealed to be divalent by ESR, SQUID, and XPS methods. Oxidation of 2Cu with two equivalents of AgBF4 gave complex 3Cu, which was characterized as a bis‐copper(II) complex of a dicationic triply‐linked corrole dimer not as the corresponding bis‐copper(III) complex. In accord with this assignment, the structural parameters around the copper ions were revealed to be quite similar for 2Cu and 3Cu. Importantly, the magnetic spin–spin interaction differs depending on the redox‐state of the ligand, being weak ferromagnetic in 2Cu and antiferromagnetic in 3Cu. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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16. Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration
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Davide Ravelli, Luca Capaldo, and Maurizio Fagnoni
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Xanthene ,Porphyrins ,Molecular Structure ,010405 organic chemistry ,Chemistry ,Review ,General Chemistry ,Hydrogen atom ,Ketones ,010402 general chemistry ,Photochemistry ,Uranyl ,01 natural sciences ,Porphyrin ,3. Good health ,0104 chemical sciences ,Dication ,chemistry.chemical_compound ,Molecule ,Eosin Y ,Bond cleavage ,Hydrogen - Abstract
Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C–H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C–H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C–C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.
- Published
- 2022
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17. Specific chemical bond relaxation unraveled by analysis of shake-up satellites in the oxygen single site double core hole spectrum of CO2
- Author
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Yasumasa Hikosaka, Anthony Ferté, Eiji Shigemasa, Richard Taïeb, Kouichi Soejima, Pascal Lablanquie, Jérôme Palaudoux, Francis Penent, Hiroshi Iwayama, Stéphane Carniato, Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of Toyama, and Niigata University
- Subjects
Chemical Physics (physics.chem-ph) ,Physics ,010304 chemical physics ,Spectrum (functional analysis) ,FOS: Physical sciences ,General Physics and Astronomy ,chemistry.chemical_element ,01 natural sciences ,Molecular physics ,Oxygen ,Spectral line ,3. Good health ,Dication ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Chemical bond ,chemistry ,[CHIM.ANAL]Chemical Sciences/Analytical chemistry ,Physics - Chemical Physics ,0103 physical sciences ,Relaxation (physics) ,Molecule ,Physical and Theoretical Chemistry ,010306 general physics ,Carbon - Abstract
We developed recently [A. Fert\'e, et al., J. Phys. Chem. Lett. 11, 4359 (2020)] a method to compute single site double core hole (ssDCH or K$^{-2}$) spectra. We refer to that method as NOTA+CIPSI. In the present paper this method is applied to the O K$^{-2}$ spectrum of the CO$_2$ molecule, and we use this as an example to discuss in detail its convergence properties. Using this approach, a theoretical spectra in excellent agreement with the experimental one is obtained. Thanks to a thorough interpretation of the shake-up states responsible for the main satellite peaks and with the help of a comparison with the O K$^{-2}$ spectrum of CO, we can highlight the clear signature of the two non equivalent carbon oxygen bonds in the oxygen ssDCH CO$_2$ dication., Comment: 16 pages, 7 figures, 7 tables
- Published
- 2022
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18. N,N‐Diphenyl Dihydrophenazines: Using π‐Extension to Access Dicationic Multifunctional Materials
- Author
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Jacopo Dosso, Maurizio Prato, Dosso, Jacopo, and Prato, Maurizio
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Dihydrophenazine ,Aromaticity ,Molecular switche ,Organic Chemistry ,electrochromism ,General Chemistry ,Dication ,Catalysis - Abstract
Dihydrophenazines are receiving increasing attention due to applications in numerous fields of chemistry, from light emission to organo-photocatalysis. Despite this growing interest and numerous works involving the preparation of radical cations based on this scaffold, the isolation and study of the aromatic dications obtained by 2 electron oxidation of dihydrophenazines is still mostly unexplored. From this point of view, along with the substitution at the N atoms generally used to tune dihydrophenazine properties, the p-extension of the phenazine core could play a crucial role in making dicationic states accessible. This could result in an extension of the knowledge on these elusive dications and in potentially highly interesting applications ranging from material science to molecular actuators.
- Published
- 2023
- Full Text
- View/download PDF
19. On the Aromaticity and 13C-NMR Pattern of Pentagonal-Pyramidal Hexamethylbenzene Dication [C6(CH3)6]2+: A {C5(CH3)5}−–{CCH3}3+ Aggregate
- Author
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Alvaro Muñoz-Castro and Desmond MacLeod-Carey
- Subjects
Chemistry ,shielding ,Chemical shift ,carbon ,Hypervalent molecule ,Aromaticity ,General Medicine ,aromaticity ,Carbon-13 NMR ,Ring (chemistry) ,DFT ,Dication ,Ion ,Crystallography ,chemistry.chemical_compound ,hypercoordination ,Hexamethylbenzene ,QD1-999 - Abstract
The experimentally characterized hexamethylbenzene dication C6(CH3)62+ shows a pentagonal-pyramidal structure involving a carbon-capped five-membered ring. The structural characterization of this hypercoordination (or hypervalency) gives rise if the aromatic behavior remains in the resulting pentagon ring. Here, we investigated the induced magnetic field of C6(CH3)62+ to gain a deeper understanding of the resulting non-classical structural situation in a representative pentagonal-pyramidal structure. Our results support the view of a C5(CH3)5−/CCH33+ structure, depicting a π-aromatic pentamethylcyclopentadienyl anion with a 6π-electron kernel, with a capped carbon which does not decrease the characteristic shielding cone property of the aromatic ring. Hence, carbon-capped rings are suggested to retain the aromatic behavior from the former aromatic ring. We expect that the analysis of both the overall magnetic response and NMR chemical shifts may be informative to unravel the characteristic patterns in the formation of hypervalent carbon atoms involving non-classical chemical environments.
- Published
- 2021
20. Iron (III) hydroxocomplex-methyl viologen dication system as a prospective tool for determination of hydroxyl radical reaction rate constants with environmental pollutants
- Author
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Yuliya E. Tyutereva, Vyacheslav P. Grivin, Feng Wu, Victor F. Plyusnin, Ivan P. Pozdnyakov, and Jing Xu
- Subjects
Paraquat ,Pollutant ,Photolysis ,Hydroxyl Radical ,Chemistry ,Iron ,Health, Toxicology and Mutagenesis ,Radical ,General Medicine ,Photochemistry ,Pollution ,Dication ,Reaction rate ,Kinetics ,chemistry.chemical_compound ,Environmental Chemistry ,Flash photolysis ,Environmental Pollutants ,Reactivity (chemistry) ,Hydroxyl radical ,Methyl Viologen ,Oxidation-Reduction ,Water Pollutants, Chemical - Abstract
Reactivity of oxidative species with target pollutants is one of the crucial parameters for application of any system based on advanced oxidation processes (AOPs). This work presents new useful approach how to determine the hydroxyl radical reaction rate constants (kOH) using UVA laser flash photolysis technique. Fe (III) hydroxocomplex at pH 3 was applied as a standard source of hydroxyl radicals and methyl viologen dication (MV2+) was used as selective probe for •OH radical. Application of MV2+ allows to determine kOH values even for compounds which do not generate themselves optically detectable transient species in reaction with hydroxyl radicals. Validity of this approach was tested on a wide range of different persistent pesticides and its main advantages and drawbacks in comparison with existing steady-state and time-resolved techniques were discussed.
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- 2021
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21. Unimolecular Double Photoionization-Induced Processes in Iron Pentacarbonyl
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Roberto Linguerri, Emelie Olsson, Raimund Feifel, Gunnar Nyman, John H. D. Eland, and Majdi Hochlaf
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Range (particle radiation) ,Internal energy ,Chemistry ,Photoionization ,Photochemistry ,Article ,Iron pentacarbonyl ,Dication ,Catalysis ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Ionization ,Physical and Theoretical Chemistry - Abstract
The dissociations of nascent Fe(CO)5++ ions created by 40.81 eV photoionization of iron pentacarbonyl have been examined using threefold and fourfold electron–ion coincidence measurements. The energies and forms of the ions have been explored by high-level calculations, revealing several new structures. The most stable form of Fe(CO)5++ has a quite different geometry from that of the neutral molecule. The dissociation pattern can be modeled as a sequence of CO evaporations followed by two-body charge separations. Each Fe(CO)n++ (n = 1–4) dication is stable in a restricted energy range; as its internal energy increases, it first ejects a neutral CO, then loses CO+ by charge separation at higher energy. In the initial stages, charge-retaining CO evaporations dominate over charge separation, but the latter become more competitive as the number of residual CO ligands decreases. At energies where ionization is mainly from the CO ligands, new Fe–C and C–C bonds are created by a mechanism which might be relevant to catalysis by Fe., Dissociations of nascent Fe(CO)5++ ions by sequential CO evaporations, leading (in restricted energy ranges) to stable Fe(CO)n++ (n = 1−4) dicationic species. At energies where ionization is mainly from the CO ligands, new Fe−C and C−C bonds are created by a mechanism which might be relevant to catalysis by Fe.
- Published
- 2021
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22. Two-Body Metastable Dissociation of n-Pentane and n-Hexane Triplet Dications in Intense Femtosecond-Laser Fields
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Masashi Tsuge, Kennosuke Hoshina, and Tatsuro Shirota
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Chemistry ,Double ionization ,Ionization ,Physics::Atomic and Molecular Clusters ,Mass spectrum ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Mass spectrometry ,HOMO/LUMO ,Molecular physics ,Dissociation (chemistry) ,Dication ,Ion - Abstract
Mass spectra of n-pentane and n-hexane ionized through femtosecond-laser pulses were measured using a time-of-flight mass spectrometer. Fragment ions ejected with large kinetic energies were identified as side peaks in which a two-body dissociation pathway, C5H12++ → C2H5+ + C3H7+, was identified for n-pentane, and two for n-hexane, C6H14++ → C2H5+ + C4H9+ and C3H7+ + C3H7+, based on momentum matching of the fragments. The two-body dissociation pathways were observed when the polarization direction of the linearly polarized laser light was perpendicular to the molecular axis. However, when the polarization direction was parallel to the molecular axis or the laser light was circularly polarized, these signals were weak or difficult to identify. These results suggest that the two-body dissociation pathways are caused by nonsequential double ionization (NSDI), which begins with ionization from the π-type second highest occupied molecular orbital (HOMO-1) via the laser electric field perpendicular to the molecular axis rather than bonding the σ-type HOMO. Quantum chemical calculations show that the dication has a triplet metastable state with the same formula as the neutral state (i.e., 3[CH3-(CH2)n-CH3]++). Therefore, the relevant two-body dissociation channels open through transition states with the (HOMO)1(HOMO-1)1 electron configuration and the estimated kinetic energy release values correlate with those observed.
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- 2021
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23. Ferromagnetic Coupling in Oxidovanadium(IV)–Porphyrin Radical Dimers
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Sabyasachi Sarkar, Eugenio Garribba, Sankar Prasad Rath, Devesh Kumar, Giuseppe Sciortino, Mohammad Usman, and Akhil Kumar Singh
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Chemistry ,Diradical ,Porphyrin ,Magnetic susceptibility ,Dication ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,Unpaired electron ,law ,Molecular orbital ,Physical and Theoretical Chemistry ,Electron paramagnetic resonance ,Cis–trans isomerism - Abstract
Three different oxidovanadium(IV) porphyrin dimers with anti, cis, and trans arrangements of the two rings have been synthesized by changing the bridge between the porphyrin macrocycles. This provides a unique opportunity to investigate the role of the bridge and spatial arrangement between the two VIVO centers for their electronic communication and magnetic coupling. They were characterized by the combined application of XRD analysis, UV-vis and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility, and DFT calculations. One- and two-electron oxidations produce mono- and dication diradical species, respectively, which display an unusual ferromagnetic interaction between the unpaired spins of vanadium(IV) and porphyrin π-cation radical, in contrast to other metalloporphyrin dimers. The oxidized species show a dissimilar behavior between cis and trans isomers. The ferromagnetic coupling occurs between the porphyrin π-cation radical and the unpaired electron of the VIVO ion on the dxy orbital, orthogonal to the porphyrin-based molecular orbitals a1u and a2u.
- Published
- 2021
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24. Dicationic-Type Quaternary Ammonium Salts as Candidates of Desiccants for an Air-Conditioning System
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Toshiyuki Itoh, Hyung J. Kim, Mariko Hiramatsu, Toshiki Nokami, Kentaro Kamada, Hiroshi Nakayama, Kenichi Yagi, and Fangyong Yan
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Desiccant ,Aqueous solution ,Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,Inorganic chemistry ,Cationic polymerization ,Solvation ,General Chemistry ,Airborne transmission ,Dication ,chemistry.chemical_compound ,chemistry ,Ionic liquid ,Environmental Chemistry ,Ammonium - Abstract
Liquid desiccant air conditioners contribute to sustainable living by reducing the electricity consumption. They can be driven with continuous ventilation and thus can prevent airborne transmission of infectious diseases like COVID-19. In order to develop efficient desiccant materials for liquid desiccant air conditioners, we have investigated the dehumidification capability of 21 types of ammonium salts, many of them being ionic liquids. The hygroscopicity of dicationic quaternary ammonium bis(dimethyl or diethylphosphate) is found to increase with the carbon chain length of the spacer group -(CH2)n- that bridges the two terminal cationic moieties of the dication, that is, (CH2)2 < (CH2)3 < (CH2)6. This trend remains unchanged when methyl substituents on the cation and the phosphate anion are replaced by ethyl groups. A high dehumidification capability is obtained for N1,N1,N1,N6,N6,N6-hexamethylhexane-1,6-diaminium bis(dimethylphosphate) ([HMC6][DMPO4]2) and 1,6-diethyl-1,1,6,6-tetramethylhexane-1,6-diaminium bis(diethylphosphate) ([DETMC6][DEPO4]2);their capability per gram reaches almost twice that of CaCl2, and their dehumidification rate is superior to popular solid desiccants. A favorable equilibrium water vapor pressure for the liquid desiccant air-conditioning system is attained for an 80% (w/w) aqueous solution of [HMC6][DMPO4]2. In addition, the 80% aqueous solution of [HMC6][DMPO4]2 affords no corrosive effect on steel, aluminum, and stainless steel and a very weak effect on copper. Dicationic quaternary ammonium bis(dimethyl or diethylphosphate)s are stable compounds;their aqueous solutions produce no odor after storing for over 1 year under ambient conditions. Molecular dynamics simulations are performed to gain insights into the solvation structure, energetics, and transport behavior of water in aqueous solutions of [HMC6][DMPO4]2 and related salts. ©
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- 2021
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25. Preparation, Structure Determination, and Electrochemical Properties of 4,5‐Dialkylbenzo[1,2‐ d :4,5‐ d’ ]bis[1,2,3]triselenoles and Their Singlet and Triplet‐State Dications
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Yohji Misaki, Yoshiki Nakanishi, Tsukasa Nakahodo, Eiichi Suzuki, Takeshi Kimura, and Satoshi Ogawa
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Chemistry ,General Chemistry ,Singlet state ,Triplet state ,Photochemistry ,Electrochemistry ,Dication - Published
- 2021
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26. Synthesis, Optical Properties, and Electrochemical Behavior of 5,10,15,20‐Tetraaryl‐5,15‐diazaporphyrin‐Amine Hybrids
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Naoya Muramatsu, Ko Furukawa, Yutaro Fujita, Yuna Satoh, Yoshihiro Matano, Mao Minoura, Haruyuki Nakano, and Tadaaki Ikoma
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Absorption spectroscopy ,Chemistry ,General Chemistry ,Electrochemistry ,Redox ,Dication ,law.invention ,Metal ,Covalent bond ,law ,visual_art ,Polymer chemistry ,visual_art.visual_art_medium ,Amine gas treating ,Electron paramagnetic resonance - Abstract
This work reports a series of covalently linked hybrids comprising 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (M-TADAP; M = Ni, Zn, Cu) and amines. M-TADAP-amine hybrids were prepared via the metal-templated cyclization of the corresponding metal(II)-dipyrrin complexes and redox reactions on the DAP unit. In the UV/vis/near-IR absorption spectra of the hybrids containing an 18π-electron DAP ring, broad charge-transfer bands were observed, reflecting the electron-donating property of the para-aminophenyl groups and the electron-accepting property of the 18π TADAP dication. The electrochemical behavior of the M-TADAP-amine hybrids was strongly dependent on the structure of the peripheral amine units. Further electrochemical oxidation of the hybrids bearing N-Ph groups conceivably generated amine-centered radicals, which sequentially underwent irreversible coupling to form benzidine-linked M-TADAP polymer films. The Ni-TADAP-benzidine polymer exhibited the electric conductivity of 1×10-3 S m-1 .
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- 2021
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27. Pyrano[3,4-c]pyrandiium dication.
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Suzdalev, Konstantin F., Krachkovskaya, Alina V., Tkachev, Valerii V., Kurbatov, Sergey V., and Aldoshin, Sergey M.
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- *
HYDROXYL group , *NUCLEAR magnetic resonance spectroscopy , *CRYSTAL structure , *HYDROLYSIS - Abstract
Pyrano[3,4- c pyrandiium dication has been detected in anhydrous D 2 SO 4 using two-dimensional correlation NMR spectroscopy. The dication is generated as an intermediate in acid-catalyzed hydrolysis of 1-ethoxy-5-methyl-3,8-diphenyl-1 H -pyrano[3,4- c pyran-7-ium perchlorate, where the action of 70% HClO 4 leads to the replacement of ethoxy group by hydroxyl one, and the reaction with SbCl 5 affords dimeric bis(hexachloroantimonate) bearing two pyrano[3,4- c pyran7-ium moieties linked via oxygen atom. The crystal structures of both isolated products have been determined. [ABSTRACT FROM AUTHOR]
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- 2020
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28. Transmission of Point Chirality to Axial Chirality for Strong Circular Dichroism in Triarylmethylium-o,o-dimers.
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Yusuke Ishigaki, Tomohiro Iwai, Yuki Hayashi, Aiichiro Nagaki, Ryo Katoono, Kenshu Fujiwara, Jun-ichi Yoshida, and Takanori Suzuki
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- *
CHIRALITY , *CIRCULAR dichroism , *DIMERS - Abstract
Triarylmethylium-o,o-dimers adopt a twisted geometry so that two diarylmethyliums are stacked in a slipped manner. Thus, chiral auxiliaries on the aryl groups induce a preference in the axial chirality of the central biphenyl unit. Strong circular dichroism is attained through exciton coupling, which can be used for additional spectral output in their electrochromic behavior. Diastereoselectivity based on p-p stacking exhibits unique solvent effects, thus endowing multifunctional response properties. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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29. The carotenoid Bixin found to exhibit the highest measured carotenoid oxidation potential to date consistent with its practical protective use in cosmetics, drugs and food.
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Tay-Agbozo, Sefadzi, Street, Shane, and Kispert, Lowell
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- *
CAROTENOIDS , *ELECTROCHEMICAL analysis , *RADICAL cations , *CANTHAXANTHIN , *CYCLIC voltammetry - Abstract
The electrochemical oxidation potentials of cis bixin correspond to the production of the carotenoid radical cation, Car + and dication Car ++ . The oxidation is a two-electron process with oxidation potentials at ~0.94 and ~1.14 V vs SCE (reference to ferrocene at 0.528 V) in THF. These potentials are higher than that of symmetrical canthaxanthin at 0.775 V and 0.972 V and for β-carotene at 0.634 V and 0.605 V respectively. The second oxidation potential for canthaxanthin is higher by 0.20 V than the first. Similar difference is observed for bixin. In contrast, the second oxidation potential for β-carotene is lower by 30 mV than that of the first. Reduction potentials were found to occur at ~−0.69 and ~−1.22 V vs SCE. The lifetime of the radical cation of cis bixin, Car + , is short and decays rapidly at ambient temperature. The suggested scavenging ability of cis bixin towards reactive oxidative oxygen species is estimated to be 44. On the other hand, that of β-carotene, symmetrical canthaxanthin and the dicyano substituted carotenoid which exhibit oxidation potentials of 0.634 V, 0.775 V and 0.833 V vs SCE were measured to be 0.64, 1.96 and 23.60 respectively. The non-reversible electrochemical measurements suggest the tendency for bixin to react with trace amounts of reactive oxygen species ( OH, O 2 − , OOH). [ABSTRACT FROM AUTHOR]
- Published
- 2018
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30. Why are reactions of 2‐ and 8‐thioquinoline derivatives with iodine different?
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Rudakov, Boris V., Stash, Adam I., Makarov, Gennady I., Matveychuk, Yury V., Zherebtsov, Dmitry A., and Bartashevich, Ekaterina V.
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- *
QUINOLINE derivatives , *IODINE , *CHEMICAL reactions - Abstract
The crystal structures of 1,2‐dihydro‐1,1′‐bi[thiazolo[3,2‐a]quinoline]‐10a,10a′‐diium diiodide hemihydrate, C22H16N2S22+·2I−·0.5H2O, and 1,2‐dihydro‐1,1′‐bi[thiazolo[3,2‐a]quinoline]‐10a,10a′‐diium iodide triiodide, C22H16N2S22+·I−·I3−, obtained during the reaction of 1,4‐bis(quinolin‐2‐ylsulfanyl)but‐2‐yne (2TQB) with iodine, have been determined at 120 K. The crystalline products contain the dication as a result of the reaction proceeding along the iodocyclization pathway. This is fundamentally different from the previously observed reaction of 1,4‐bis(quinolin‐8‐ylsulfanyl)but‐2‐yne (8TQB) with iodine under similar conditions. A comparative analysis of the possible conformational states indicates differences in the relative stabilities and free rotation for the 2‐ and 8‐thioquinoline derivatives which lead to a disparity in the convergence of the potential reaction centres for 2TQB and 8TQB. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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31. Air-stable diradical dications with ferromagnetic interaction exceeding the thermal energy at room temperature: from a monomer to a dimer.
- Author
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Wenqing Wang, Lei Wang, Sheng Chen, Wenbang Yang, Zaichao Zhang, and Xinping Wang
- Abstract
Two tetraazacyclophane dications (1
2+ and 22+ ) with different remote substituents have been synthesized, isolated and characterized. Their electronic structures and physical property were studied by various spectroscopic techniques, single crystal X-ray diffraction, super conducting quantum interference device (SQUID) measurements and theoretical calculations. The dications have triplet ground states with ferromagnetic interaction exceeding the thermal energy at room temperature. The solid-state structures of these species were tunable by substituent effect, with 12+ as a monomer and 22+ as a dimer. [ABSTRACT FROM AUTHOR]- Published
- 2018
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32. A Copper(I) Complex with Two Unpaired Electrons, Synthesised by Oxidation of a Copper(II) Complex with Two Redox‐Active Ligands
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Michael Zharnikov, Elisabeth Kaifer, Marco Werr, Hans-Jörg Himmel, Andika Asyuda, and Markus Enders
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Ligand ,Chemistry ,alcohol oxidation ,chemistry.chemical_element ,General Chemistry ,radicals ,Copper Complexes | Hot Paper ,Copper ,Redox ,Catalysis ,Dication ,Azine ,chemistry.chemical_compound ,Electron transfer ,urea azines ,Unpaired electron ,copper ,Polymer chemistry ,Homoleptic ,Research Articles ,Research Article ,redox-induced electron transfer - Abstract
Two homoleptic copper(II) complexes [Cu(L1)2] and [Cu(L2)2] with anionic redox‐active ligands were synthesised, one with urea azine (L1) and the other with thio‐urea azine (L2) ligands. One‐electron oxidation of the complexes initiates an unprecedented redox‐induced electron transfer process, leading to monocationic copper(I) complexes [Cu(L1)2]+ and [Cu(L2)2]+ with two oxidised ligands. While [Cu(L1)2]+ is best described as a CuI complex with two neutral radical ligands that couple antiferromagnetically, [Cu(L2)2]+ is a CuI complex with two clearly different ligand units in the solid state and with a magnetic susceptibility close to a diamagnetic compound. Further one‐electron oxidation of the complex with L1 ligands results in a dication [Cu(L1)2]2+, best described as a CuI complex with a twofold oxidised, monocationic ligand and a neutral radical ligand. The stability in at least three redox states, the accumulation of spin density at the ligands and the facile ligand‐metal electron transfer make these complexes highly attractive for a variety of applications; here the catalytic aerobic oxidation of alcohols to aldehydes is tested., Oxidation‐induced reduction: The oxidation of mononuclear CuII complexes with novel unsymmetric redox‐active urea azine or thio‐urea azine ligands leads to metal reduction and formation of complexes with intriguing electronic structures. The stability in several redox states is the basis for their first application in catalytic aerobic alcohol oxidation.
- Published
- 2021
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33. Radically Enhanced Dual Recognition
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Xingang Zhao, J. Fraser Stoddart, Bo Song, Xiao-Yang Chen, Dengke Shen, Yong Wu, Kang Cai, Yang Jiao, Long Zhang, Haochuan Mao, Huang Wu, Hongliang Chen, Yuanning Feng, Charlotte L. Stern, and Michael R. Wasielewski
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Chemistry ,Diradical ,Cooperativity ,Viologen ,General Medicine ,General Chemistry ,Catalysis ,law.invention ,Dication ,Crystallography ,Molecular recognition ,Radical ion ,law ,medicine ,Molecule ,Electron paramagnetic resonance ,medicine.drug - Abstract
Complexation between a viologen radical cation (V.+ ) and cyclobis(paraquat-p-phenylene) diradical dication (CBPQT2(.+) ) has been investigated and utilized extensively in the construction of mechanically interlocked molecules (MIMs) and artificial molecular machines (AMMs). The selective recognition of a pair of V.+ using radical-pairing interactions, however, remains a formidable challenge. Herein, we report the efficient encapsulation of two methyl viologen radical cations (MV.+ ) in a size-matched bisradical dicationic host - namely, cyclobis(paraquat-2,6-naphthalene)2(.+) , i.e., CBPQN2(.+) . Central to this dual recognition process was the choice of 2,6-bismethylenenaphthalene linkers for incorporation into the bisradical dicationic host. They provide the space between the two bipyridinium radical cations in CBPQN2(.+) suitable for binding two MV.+ with relatively short (3.05-3.25 A) radical-pairing distances. The size-matched bisradical dicationic host was found to exhibit highly selective and cooperative association with the two MV.+ in MeCN at room temperature. The formation of the tetrakisradical tetracationic inclusion complex - namely, [(MV)2 ⊂CBPQN]4(.+) - in MeCN was confirmed by VT 1 H NMR, as well as by EPR spectroscopy. The solid-state superstructure of [(MV)2 ⊂CBPQN]4(.+) reveals an uneven distribution of the binding distances (3.05, 3.24, 3.05 A) between the three different V.+ , suggesting that localization of the radical-pairing interactions has a strong influence on the packing of the two MV.+ inside the bisradical dicationic host. Our findings constitute a rare example of binding two radical guests with high affinity and cooperativity using host-guest radical-pairing interactions. Moreover, they open up possibilities of harnessing the tetrakisradical tetracationic inclusion complex as a new, orthogonal and redox-switchable recognition motif for the construction of MIMs and AMMs.
- Published
- 2021
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34. High Site Selectivity in Electrophilic Aromatic Substitutions: Mechanism of C–H Thianthrenation
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Tobias Ritter, Fabio Juliá, Xiao-Song Xue, Qianzhen Shao, Javier Mateos, Kendall N. Houk, Meng Duan, Chenxi Lu, Matthew B. Plutschack, and Florian Berger
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Aryl ,Halogenation ,Regioselectivity ,General Chemistry ,Biochemistry ,Borylation ,Combinatorial chemistry ,Catalysis ,Article ,Dication ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Electrophile ,Selectivity ,Thianthrene - Abstract
The introduction of thianthrene as a linchpin has proven to be a versatile strategy for the C-H functionalization of aromatic compounds, featuring a broad scope and fast diversification. The synthesis of aryl thianthrenium salts has displayed an unusually high para regioselectivity, notably superior to those observed in halogenation or borylation reactions for various substrates. We report an experimental and computational study on the mechanism of aromatic C-H thianthrenation reactions, with an emphasis on the elucidation of the reactive species and the nature of the exquisite site selectivity. Mechanisms involving a direct attack of arene to the isolated O-trifluoracetylthianthrene S-oxide (TT+-TFA) or to the thianthrene dication (TT2+) via electron transfer under acidic conditions are identified. A reversible interconversion of the different Wheland-type intermediates before a subsequent, irreversible deprotonation is proposed to be responsible for the exceptional para selectivity of the reaction.
- Published
- 2021
35. Effect of Bulky Anion around the Dication on the Electronic Structure and Normal Frequencies in 1,3-Bis(3-methylimidazolium-1-yl)propane Bis(trifluoromethanesulfonyl)imide Ionic Liquid
- Author
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Dmitry Isaev, Sherly Latortue, Kyung Seol, Michelle Helminen, Nilesh R. Dhumal, and Brooke Williams
- Subjects
Quantitative Biology::Biomolecules ,Hydrogen bond ,Chemistry ,General Chemical Engineering ,General Chemistry ,Electronic structure ,Article ,Ion ,Dication ,Crystallography ,chemistry.chemical_compound ,Ionic liquid ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Physics::Chemical Physics ,Imide ,Conformational isomerism ,QD1-999 - Abstract
A manifestation of hydrogen bonding between the dication and anions attributed to their relative position of the anions around the cation can influence both the conformational equilibrium and the physical properties of ionic liquids. With this view, we studied the electronic structure and normal frequencies using density functional theory calculations to analyze the hydrogen-bonding interactions in dicationic ionic liquids. The conformers are distinguished based on the hydrogen-bonding sites of the cation and anion. The weak hydrogen bonding between the dication and anions in dication ionic liquids can lead to greater conformational equilibrium compared to the monocation system. Consequences of these interactions for the vibrational spectrum are analyzed to provide an insight into the conformational equilibrium in dicationic ionic liquids at the molecular level.
- Published
- 2021
36. THEORETICAL EXPLANATION FOR CATALYTIC HYDROSILYLATION OF SOME ORGANIC MOLECULES MEDIATED BY A PHOSPHORUS DICATION COMPOUND
- Author
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Cem Burak Yildiz
- Subjects
Reaction mechanism ,Basic Sciences ,Hydrosilylation ,Temel Bilimler ,Phosphorus ,chemistry.chemical_element ,General Medicine ,Photochemistry ,Reaction mechanism,DFT,catalysis,Phosphorus ,Dication ,Catalysis ,Organic molecules ,chemistry.chemical_compound ,chemistry ,DFT,catalysis,Phosphorus,Reaction mechanism - Abstract
Catalysis reactions under metal-free and ambient conditions have received great interest in terms of economic and environmental issues. Especially, the applications of Lewis acids for the processes are having special interest due to their unique roles in a huge number of organic reactions. In this sense, a recent compound PIII dication has played an important role in the catalytic hydrosilylation of carbonyls and olefins. Herein theoretical calculations were carried out to elucidate the mechanisms of the experimentally reported and unknown reactions. The proposed mechanisms show that the reactions of a-d can occur spontaneously, whereas the formation of pyridine has endergonic nature.
- Published
- 2021
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37. Black HPHAC: Synthesis and properties of dinitroHPHAC and its reduced global aromaticity in the dication state
- Author
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Yoshino Fujikawa, Masayoshi Takase, Yoshiki Sasaki, and Hidemitsu Uno
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chemistry.chemical_compound ,Computational chemistry ,Chemistry ,Nitration ,Aromaticity ,General Chemistry ,State (functional analysis) ,Dication - Abstract
Introduction of functional groups on a [Formula: see text]-conjugated system is one of the most promissing methods to modulate their chemical and physical properties. Here, dinitrohexapyrrolohexaazacoronene (dinitroHPHAC) was synthesized, in which two nitro groups are introduced at the same pyrrole ring. The dinitroHPHAC possesses a large dipole moment ([Formula: see text] = 11.7 D at B3LYP/6-31G(d,p)) and showed solvatochromism with decreased HOMO-LUMO energy gap. Interestingly, the colour of the solid is black to the naked eye. The global aromaticity of the dication state is decreased compared with those of pristine HPHAC and mononitroHPHAC.
- Published
- 2021
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38. Synthesis and Structural Elucidation of Bisdibenzocorannulene in Multiple Redox States
- Author
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Chenxin Yang, Sheng Xie, Wangwang Peng, Huiping Xiao, Bo Li, Xinhao Wang, Jishan Wu, Shenglian Luo, Guangwu Li, and Zebing Zeng
- Subjects
Steric effects ,Diradical ,Chemistry ,General Medicine ,General Chemistry ,Photochemistry ,Redox ,Catalysis ,Dication ,Metal ,Delocalized electron ,visual_art ,visual_art.visual_art_medium ,Singlet state ,Antiaromaticity - Abstract
We report an anti-folded bowl-shaped bisdibenzocorannulene (BDBC) featuring a new chair-cyclohexane-like hexagon as a bridge of two dibenzocorannulene moieties. The neutral compound showed multiple redox-active properties and could be converted to the corresponding redox states through chemical reduction or oxidation. Chemical reduction of BDBC by stoichiometric addition of metallic potassium in the presence of [18]crown-6 ether, provided a radical anion BDBC.- and a dianion BDBC2- , respectively; while chemical oxidation by silver hexafluoroantimonate(V), converted the neutral compound to an open-shell singlet diradical dication (BDBC.. )2+ . The structural consequences of both electron-reduction and oxidation were closely related to the release of ring-strain of the bowl-shaped π-scaffold and imposed steric hindrance of the hexagonal bridge. In addition, the unusual open-shell nature of the dication could mainly be attributed to the changing of localized antiaromaticity in the closed-shell structure to delocalized character in the biradical, and thus the emergence of weakly bonded π-electrons.
- Published
- 2021
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39. Chemical Reduction of NiII Cyclam and Characterization of Isolated NiI Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry
- Author
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Evan Perez, Fabian S. Menges, David J. Charboneau, Sean C. Edington, Nilay Hazari, and Mark A. Johnson
- Subjects
chemistry.chemical_compound ,Crystallography ,Electron transfer ,chemistry ,Ligand ,Electrospray ionization ,Cyclam ,Infrared spectroscopy ,Physical and Theoretical Chemistry ,Mass spectrometry ,Dication ,Ion - Abstract
NiII cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) is an efficient catalyst for the selective reduction of CO2 to CO. A crucial elementary step in the proposed catalytic cycle is the coordination of CO2 to a NiI cyclam intermediate. Isolation and spectroscopic characterization of this labile NiI species without solvent has proven to be challenging, however, and only partial IR spectra have previously been reported using multiple photon fragmentation of ions generated by gas-phase electron transfer to the NiII cyclam dication at 300 K. Here, we report a chemical reduction method that efficiently prepares NiI cyclam in solution. This enables the NiI complex to be transferred into a cryogenic photofragmentation mass spectrometer using inert-gas-mediated electrospray ionization. The vibrational spectra of the 30 K ion using both H2 and N2 messenger tagging over the range 800-4000 cm-1 were then measured. The resulting spectra were analyzed with the aid of electronic structure calculations, which show strong method dependence in predicted band positions and small molecule activation. The conformational changes of the cyclam ligand induced by binding of the open shell NiI cation were compared with those caused by the spherical, closed-shell LiI cation, which has a similar ionic radius. We also report the vibrational spectrum of a NiI cyclam complex with a strongly bound O2 ligand. The cyclam ligand supporting this species exhibits a large conformational change compared to the complexes with weakly bound N2 and H2, which is likely due to significant charge transfer from Ni to the coordinated O2.
- Published
- 2021
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40. Nickel(II)-SNS Thiolate Complexes: Reactivity and Solution Dynamics
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R. Tom Baker, Jeffrey S. Ovens, Jessica Martin, and Yahya M. Albkuri
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chemistry.chemical_classification ,Denticity ,010405 organic chemistry ,Ligand ,Protonation ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Coordination complex ,Dication ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Reactivity (chemistry) ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Carbene - Abstract
Nickel coordination chemistry with a biomimetic thiolate-imine-thioether SNSMe ligand is accompanied by diverse reactivity and multidentate ligand dynamics. Reaction of Ni(acac)2 with 2 equiv of 2-(methylthio)-phenyl-benzothiazolidine (MPB) affords the bis(arylimino-phenylene-thiolate) complex Ni(κ2-SNSMe)2 (1; acac = acetylacetonate). Thermolysis of 1 in refluxing toluene is accompanied by imine C-C bond formation, yielding [Ni(N2S2)] (2) with a redox-active ligand. Protonation of 1 with NHTf2 at a low temperature released 1 equiv of MPB, yielding crystals of the dimeric dication {[Ni(μ-κ3-SNSMe)]2}(NTf2)2 (3; Tf = SO2CF3) in high yield. In contrast, the same reaction at room temperature gave also paramagnetic complexes {Ni[μ-Ni(κ3-SNSMe)2]2}(NTf2)2 (4) and {Ni[μ-Ni(κ3-SNSMe)2]3}(NTf2)2 (5) that feature coordination of two or three pseudo-octahedral, paramagnetic Ni(κ3-SNSMe)2 units to a central Ni(II) dication via thiolate bridges. Remarkably, dissolution of 3 in a variety of solvents, including weakly coordinating CH2Cl2, rapidly generates a mixture of 4 and Ni(NTf)2. Treatment of this mixture with Lewis bases L gave high yields of dimers {[Ni(μ-κ3-SNSMe)L]2}(NTf2)2 for L = CNXylyl (6a) and {[Ni(μ-κ3-SNSMe)]2(μ-dmpm)}(NTf2)2 (6b; dmpm = bis(dimethylphosphino)methane) or monomers [Ni(κ3-SNSMe)L](NTf2) for L = PMe3 (7a) and P(OMe)3 (7b). Addition of 2 equiv of the strong donor N-heterocyclic carbene ligand, IPr, to 3, however, led to thioether demethylation, affording neutral dithiolate complex Ni(κ3-SNS)(IPr) (8). Reaction products were characterized by NMR and mass spectrometry and complexes 1-5, 6a, 6b, 7a, and 8 by single-crystal X-ray diffraction.
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- 2021
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41. 3,3′-(Dodecane-1,12-diyl)bis(1-methylimidazolium) 5,5′-azotetrazolate heptahydrate
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Gerhard Laus, Klaus Wurst, and Herwig Schottenberger
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crystal structure ,azotetrazolate ,dianion ,dication ,imidazole ,Crystallography ,QD901-999 - Abstract
The title compound, C20H36N4·C2N10·7H2O, was obtained by reaction of 1-methylimidazole with 1,12-dibromododecane, followed by repeated ion metathesis (bromide → sulfate → azotetrazolate). An intricate network of hydrogen bonds is formed between anions and water molecules, leading to a layered arrangement parallel to (101).
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- 2017
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42. Isomerization Dynamics in the Symmetric and Asymmetric Fragmentation of Ethane Dications
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Yu Zhang, Li Chen, Chow-Shing Lam, Yaming Zou, Baoren Wei, Bo Wang, Baihui Ren, Jie Han, Kai-Chung Lau, and Long Wei
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Chemistry ,Coulomb explosion ,Ab initio ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Dissociation (chemistry) ,Dication ,Fragmentation (mass spectrometry) ,0103 physical sciences ,General Materials Science ,Singlet state ,Physical and Theoretical Chemistry ,Triplet state ,010306 general physics ,0210 nano-technology ,Isomerization - Abstract
Hydrogen- or proton-migration-induced isomerization has recently been of concern for its critical role in the dissociation of organic molecules of astrophysical or biological relevance. Herein we present a combined experimental and theoretical study of the two-body C-C bond breakdown dissociation of ethane dication. For the asymmetric fragmentation channel CH2+ + CH4+, the kinetic energy release measurements and ab initio quantum chemical calculations demonstrate that the reaction pathway involving hydrogen-migration-induced isomerization of [CH3-CH3]2+ to [CH2-CH4]2+ can be accessed via the lowest triplet state rather than the ground singlet state of ethane dication. Interestingly, it is found that a considerable proportion of the yield of symmetric fragmentation CH3+ + CH3+, which is usually considered from a direct Coulomb explosion and seemingly independent of isomerization, could come from the dissociation of ethane dication in the ground singlet state with the involvement of [CH3-CH3]2+ isomerization to intermediate [H2C(H2)CH2]2+ of the diborane-like double-bridged structure.
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- 2021
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43. Highly Coordinated Heteronuclear Calcium–Iron Carbonyl Cation Complexes [CaFe(CO)n]+ (n=5–12) with d−d Bonding
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Lili Zhao, Guanjun Wang, Mingfei Zhou, Yuna Bai, Yangyu Zhou, Xiaoyang Jin, and Gernot Frenking
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heteronuclear complexes ,010405 organic chemistry ,Chemistry ,Communication ,Photodissociation ,Matrix isolation ,Infrared spectroscopy ,matrix isolation ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,Communications ,0104 chemical sciences ,Dication ,Ion ,Crystallography ,bonding analysis ,Heteronuclear molecule ,Transition metal ,Molecule ,Coordination Chemistry | Very Important Paper ,quantum chemical calculations ,infrared spectroscopy - Abstract
Heteronuclear calcium–iron carbonyl cation complexes in the form of [CaFe(CO)n]+ (n=5–12) are produced in the gas phase. Infrared photodissociation spectroscopy in conjunction with quantum chemical calculations confirm that the n=10 complex is the coordination saturated ion where a Fe(CO)4 fragment is bonded with a Ca(CO)6 fragment through two side‐on bridging carbonyl ligands. Bonding analysis indicates that it is best described by the bonding interactions between a [Ca(CO)6]2+ dication and an [Fe(CO)4]− anion forming a Fe→Ca d−d dative bond in the [(CO)6Ca–Fe(CO)4]+ structure, which enriches the pool of experimentally observed complexes of calcium that mimic transition metal compounds. The molecule is the first example of a heteronuclear carbonyl complex featuring a d−d bond between calcium and a transition metal., The [CaFe(CO)10]+ cation is characterized to be a coordination saturated ion where a Fe(CO)4 fragment is bonded with a Ca(CO)6 moiety through two side‐on bridging carbonyl ligands. The complex is best described by the bonding interactions between a [Ca(CO)6]2+ dication and an [Fe(CO)4]− anion forming a Fe−Ca d−d dative bond that is enhanced by the attraction between Ca and the bridging CO ligands.
- Published
- 2021
44. Isolation of Neutral, Mono‐, and Dicationic B 2 P 2 Rings by Diphosphorus Addition to a Boron−Boron Triple Bond
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Rian D. Dewhurst, Felipe Fantuzzi, Tom E. Stennett, Ivo Krummenacher, Holger Braunschweig, Tobias Brückner, and Bernd Engels
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chemistry.chemical_classification ,Diphosphorus ,010405 organic chemistry ,Radical ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Triple bond ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Dication ,chemistry.chemical_compound ,Crystallography ,chemistry ,Radical ion ,QD ,Singlet state ,Counterion ,ddc:546 ,Boron - Abstract
The NHC-stabilised diboryne (B\(_2\)(SIDep)\(_2\); SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P−P bond activation with tetraethyldiphosphine at room temperature to form a B\(_2\)P\(_2\) heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B−B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B\(_2\)P\(_2\) rings, with their diradicaloid, planar-ring isomers lying close in energy.
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- 2021
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45. Crystal structure of 3,14-dimethyl-2,13-diaza-6,17-diazoniatricyclo[16.4.0.07,12]docosane bis(perchlorate) from synchrotron X-ray data
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Sunghwan Jeon, Dohyun Moon, and Jong-Ha Choi
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crystal structure ,Crystallography ,synchrotron radiation ,Hydrogen bond ,Chlorate ,Protonation ,General Chemistry ,Crystal structure ,perchlorate ,hydrogen bonding ,Condensed Matter Physics ,Dication ,chemistry.chemical_compound ,Perchlorate ,chemistry ,QD901-999 ,General Materials Science ,Diazo ,Hydrate ,protonated macrocycle - Abstract
The crystal structure of the title salt, C20H42N4 2+·2ClO4 −, has been determined using synchrotron radiation at 220 (2) K. The structure determination reveals that protonation has occurred at diagonally opposite amine N atoms. The asymmetric unit comprises one half of the organic dication, which lies about a center of inversion, and one perchlorate anion. The macrocyclic dication adopts the most stable endodentate trans-III conformation. The crystal structure is stabilized by intramolecular N—H...N, and intermolecular N—H...O and C–H...O hydrogen bonds involving the macrocycle N—H and C—H groups as donors and the O atoms of perchlorate anions as acceptors, giving rise to a three-dimensional network.
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- 2021
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46. Metal Affinity/Selectivity of Monophosphate-Containing Signaling/Lipid Molecules
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Todor Dudev, Cédric Grauffel, and Carmay Lim
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Models, Molecular ,Cell signaling ,Stereochemistry ,01 natural sciences ,Cell membrane ,chemistry.chemical_compound ,0103 physical sciences ,Guanosine monophosphate ,Cyclic AMP ,medicine ,Magnesium ,Phosphatidylinositol ,Physical and Theoretical Chemistry ,Cyclic GMP ,Phosphatidylethanolamine ,Molecular Structure ,010304 chemical physics ,Lipids ,Adenosine ,Computer Science Applications ,Dication ,medicine.anatomical_structure ,chemistry ,Second messenger system ,Thermodynamics ,Calcium ,medicine.drug - Abstract
Monophosphate, an essential component of nucleic acids, as well as cell membranes and signaling molecules, is often bound to metal cations. Despite the biological importance of monophosphate-containing cell-signaling or lipid molecules, their propensity to bind the two most abundant cellular dications, Mg2+ and Ca2+, in a particular mode (inner/outer shell, mono/bidentate) is not well understood. Whether they prefer binding to Mg2+ than to Ca2+ and if they can outcompete the carboxylates of excitatory Asp/Glu and inhibitory gamma-aminobutyric acid (GABA) neurotransmitters in binding to Mg2+/Ca2+ remain unclear. To address these questions, we modeled cyclic adenosine/guanosine monophosphate (cAMP/cGMP), nucleoside 2',3'-cyclic phosphate, phosphatidylinositol (PI), phosphatidylserine (PS), and phosphatidylethanolamine (PEA) and determined their most stable metal-binding modes, including those of Asp/Glu and GABA, as well as their selectivity for Mg2+/Ca2+ using density functional theory combined with the polarizable continuum model. The results obtained, which are consistent with the available experimental findings, reveal that the structurally and functionally diverse monophosphate-containing ligands studied prefer monodentate coordination of Mg2+ because of the greater strain encountered upon bidentate coordination, whereas the larger Ca2+ imposes less strain upon bidentate binding and has reduced/no preference for monodentate coordination. We further show that in a low-dielectric environment, negatively charged monophosphate-containing ligands favor the better charge-accepting dication, that is, Mg2+ rather than Ca2+. By promoting Mg2+ over Ca2+ binding, signaling monophosphates (cAMP/cGMP) do not entrap cellular Ca2+ and interfere with signal transduction processes employing Ca2+ as a second messenger. In regions with high glutamate cytoplasmic concentration, glutamate may sequester Mg2+ bound to isolated five-/six-membered ring phosphates, PI, or neutral PEA, but not anionic phospholipids constituting the inner leaflet of the cell membrane.
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- 2021
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47. Crystal structure and Hirshfeld surface analysis of trans-2,5-dimethylpiperazine-1,4-diium tetrachloridocobaltate(II)
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Meriem Landolsi and Sonia Abid
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Quantitative Biology::Biomolecules ,crystal structure ,biology ,tetrachloridocobaltate(II) salt ,Chemistry ,Hydrogen bond ,Cyclohexane conformation ,General Chemistry ,Crystal structure ,Condensed Matter Physics ,biology.organism_classification ,Ring (chemistry) ,Research Communications ,Dication ,Crystal ,lcsh:Chemistry ,Crystallography ,Piperazine ,chemistry.chemical_compound ,lcsh:QD1-999 ,hirshfeld surface analysis ,Tetra ,General Materials Science ,tetrachloridocobaltate(ii) salt - Abstract
In the title molecular salt, (C6H16N2)[CoCl4], the complete dication is generated by crystallographic inversion symmetry and the piperazine ring adopts a chair conformation with the pendant methyl groups in equatorial orientations. The complete dianion is generated by crystallographic twofold symmetry. In the crystal, the (C6H16N2)2+ and [CoCl4]2− ions are linked by N—H⋯Cl and C—H⋯Cl hydrogen bonds, thereby forming a two-dimensional supramolecular network., In the title molecular salt, (C6H16N2)[CoCl4], the complete dication is generated by crystallographic inversion symmetry and the piperazine ring adopts a chair conformation with the pendant methyl groups in equatorial orientations. The complete dianion is generated by crystallographic twofold symmetry. In the crystal, the (C6H16N2)2+ and [CoCl4]2− ions are linked by N—H⋯Cl and C—H⋯Cl hydrogen bonds, thereby forming a two-dimensional supramolecular network. The Hirshfeld surface analysis and fingerprint plots reveal that the largest contributions to the crystal stability come from H⋯Cl/Cl⋯H (68.4%) and H⋯H (27.4%) contacts.
- Published
- 2021
48. Key Mechanistic Features of the Silver(I)-Mediated Deconstructive Fluorination of Cyclic Amines: Multistate Reactivity versus Single-Electron Transfer
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Jose B. Roque, Richmond Sarpong, and Djamaladdin G. Musaev
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Silver ,Hydrocarbons, Fluorinated ,Halogenation ,Molecular Conformation ,Electrons ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Article ,Catalysis ,Electron Transport ,chemistry.chemical_compound ,Electron transfer ,Colloid and Surface Chemistry ,Fluorinated ,Singlet state ,Amines ,Decarbonylation ,Iminium ,General Chemistry ,Oxidative addition ,Hydrocarbons ,0104 chemical sciences ,Dication ,chemistry ,Cyclization ,Chemical Sciences ,Hemiaminal ,Quantum Theory ,Selectfluor ,Oxidation-Reduction - Abstract
Density functional calculations have provided evidence that a Ag(I)-mediated deconstructive fluorination of N-benzoylated cyclic amines (LH) with Selectfluor [(F–TEDA)-(BF(4))(2)] begins with an association of the reactants to form a singlet state adduct {[(LH)–Ag]–[F–TEDA](2+)}. The subsequent formation of an iminium ion intermediate, [L(+)–Ag]–HF–[TEDA](+), is, formally, a Ag(I)-mediated hydride abstraction event that occurs in two steps: (a) a formal oxidative addition (OA) of [F–TEDA](2+) to the Ag(I) center that is attended by an electron transfer (ET) from the substrate (LH) to the Ag center (i.e., OA + ET, this process can also be referred to as a F-atom coupled electron transfer), followed by (b) H-atom abstraction from LH by the Ag-coordinated F atom. The overall process involves lower-lying singlet and triplet electronic states of several intermediates. Therefore, we formally refer to this reaction as a two-state reactivity (TSR) event. The C─C bond cleavage/fluorination of the resulting hemiaminal intermediate via a ring-opening pathway has also been determined to be a TSR event. A competing deformylative fluorination initiated by hemiaminal to aldehyde equilibration involving formyl H-atom abstraction by a TEDA(2+) radical dication, decarbonylation, and fluorination of the resulting alkyl radical by another equivalent of Selectfluor may also be operative in the latter step.
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- 2021
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49. The electronic structure and deexcitation pathways of an isolated metalloporphyrin ion resolved by metal L-edge spectroscopy
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Kaan Atak, Bernd von Issendorff, J. Tobias Lau, Xin Wang, Christine Bülow, S. Klumpp, Piter S. Miedema, Thomas Schlathölter, Sadia Bari, Simone Techert, Meiyuan Guo, Simon Dörner, Martin Timm, Lucas Schwob, Kaja Schubert, V. Zamudio-Bayer, and Quantum interactions and structural dynamics
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Materials science ,Large scale facilities for research with photons neutrons and ions ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Antibonding molecular orbital ,01 natural sciences ,Metal L-edge ,0104 chemical sciences ,3. Good health ,Ion ,Dication ,Chemistry ,ddc:540 ,Mass spectrum ,Molecular orbital ,0210 nano-technology ,Ground state - Abstract
The local electronic structure of the metal-active site and the deexcitation pathways of metalloporphyrins are crucial for numerous applications but difficult to access by commonly employed techniques. Here, we applied near-edge X-ray absorption mass spectrometry and quantum-mechanical restricted active space calculations to investigate the electronic structure of the metal-active site of the isolated cobalt(iii) protoporphyrin IX cation (CoPPIX+) and its deexcitation pathways upon resonant absorption at the cobalt L-edge. The experiments were carried out in the gas phase, thus allowing for control over the chemical state and molecular environment of the metalloporphyrin. The obtained mass spectra reveal that resonant excitations of CoPPIX+ at the cobalt L3-edge lead predominantly to the formation of the intact radical dication and doubly charged fragments through losses of charged and neutral side chains from the macrocycle. The comparison between experiment and theory shows that CoPPIX+ is in a 3A2g triplet ground state and that competing excitations to metal-centred non-bonding and antibonding σ* molecular orbitals lead to distinct deexcitation pathways., Near-edge X-ray absorption mass spectrometry (NEXAMS) and restricted active space (RAS) quantum mechanical calculations at the metal L-edge reveal the electronic structure and orbital-specific deexcitation pathways of gas-phase metalloporphyrins.
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- 2021
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50. Comparative Approach to Interaction of Zinc Dication with Theobromine and Theophilline-A DFT Treatment
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Lemi Türker
- Subjects
chemistry.chemical_element ,02 engineering and technology ,Zinc ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Dication ,chemistry ,Computational chemistry ,medicine ,0210 nano-technology ,Theobromine ,medicine.drug - Abstract
Two isomeric methylxanthines, theobromine and theophilline, and their Zn+2 containing composites are considered within the restrictions of density functional theory (B3LYP/ 6-31++G(d,p)). Certain quantum chemical, thermodynamic and spectral data have been harvested, compared and interpreted. The results revealed that theophilline+Zn+2 system is thermodynamically more exothermic, more favorable and electronically stable compared to the analogous system, theobromine+Zn+2.
- Published
- 2021
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