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This document summarizes a study on the use of chiral iron porphyrin complexes as catalysts for remote enantioselective epoxidation reactions. The study found that catalysts with an elongated linker were most effective for olefins that were four carbon atoms away from the lactam binding site. The presence of a hydrogen-bonding interaction between the catalyst and the substrate was also important for achieving high enantioselectivity. However, a high enantioselectivity could only be achieved if the substrate binding offered a kinetic advantage compared to a racemic catalyst. The study provides valuable insights into the factors that influence the enantioselectivity of epoxidation reactions. [Extracted from the article]

The isoalloxazine heterocycle of flavin cofactors reacts with various nucleophiles to form covalent adducts with important functions in enzymes. Molecular flavin models allow for the characterization of such adducts and the study of their properties. A fascinating set of reactions occurs when flavins react with hydroxide base, which leads to imidazolonequinoxalines, ring‐contracted flavins, with so far unexplored activity. We report a systematic study of the photophysical properties of this new chromophore by absorption and emission spectroscopy as well as cyclic voltammetry. Excited, ring‐contracted flavins are significantly stronger hydrogen atom abstractors when compared to the parent flavins, which allowed the direct trifluoromethylthiolation of aliphatic methine positions (bond dissociation energy (BDE) of 400.8 kJ mol−1). In an orthogonal activity, their increased triplet energy (E(S0←T1)=244 kJ mol−1) made sensitized reactions possible which exceeded the power of standard flavins. Combining both properties, ring‐contracted flavin catalysts enabled the one‐pot, five‐step transformation of α‐tropolone into trans‐3,4‐disubstituted cyclopentanones. We envision this new class of flavin‐derived chromophores to open up new modes of reactivity that are currently impossible with unmodified flavins. [ABSTRACT FROM AUTHOR]

Maneb is a manganese(II)‐containing fungicide with a multi‐site effect and no resistance, therefore it is widely applied in many parts of the world. There is, however, mounting evidence for neurotoxic effects with Parkinson‐like symptoms (manganism) related to usage of Maneb. Due to its insolubility in most solvents and its paramagnetism, structural elucidation is not trivial, and thus its exact molecular structure remains unknown. We report herein a synthesis procedure to prepare Maneb reproducibly in pure form and the use of various analytical techniques including X‐ray diffraction, X‐ray absorption spectroscopy and electron diffraction to determine the molecular structure of Maneb in the solid state and also in solution. [ABSTRACT FROM AUTHOR]

Along with the adoption of three-dimensional electron diffraction (3D ED/MicroED) as a mainstream tool for structure determination from sub-micron single crystals, questions about best practices regarding each step along the workflow, from data collection to structure solutions, arise. In this paper, we discuss three particular aspects of a 3D ED/MicroED experiment which, after hundreds of structures solved in Rigaku's laboratories, we have found to be important to consider carefully. First, for a representative model system of a hydrated compound (trehalose dihydrate), we show that cryo-transfer of the sample into the diffractometer is an effective means to prevent dehydration, while cooling of the sample without cryo-transfer yields a marginal improvement only. Next, we demonstrate for a small (tyrosine) and a large (clarithromycin) organic compound, how a simplified and fast workflow for dynamical diffraction calculations can determine absolute crystal structures with high confidence. Finally, we discuss considerations and trade-offs for choosing an optimal effective crystal-to-detector distance; while a long distance is mandatory for a protein (thaumatin) example, even a small molecule with difficult diffraction behavior (cystine) yields superior results at longer distances than the one used by default. [ABSTRACT FROM AUTHOR]

Copper(I)‐catalyzed domino reactions of 2‐azido sulfoximines with 1‐iodoalkynes yield fused triazolyl‐containing benzothiadiazine‐1‐oxides. The protocol features the synthesis of two fused heterocyclic rings in one step with good to excellent yields and a broad functional group tolerance. Detailed mechanistic investigations indicate that a copper π‐complex initiates a cycloaddition and oxidative C−N coupling reaction sequence. The results suggest an interrupted domino process involving an iodinated triazole as a key intermediate. [ABSTRACT FROM AUTHOR]

The synthesis of the gold(I) alkynyl-fluorene compound 2 containing a diphosphane (dppb = 1,4-bisdiphenylphosphanebutane) has been easily achieved by the treatment of the previously synthesized [2-ethynylfluorene-Au]n polymer (1) and the corresponding dppb diphosphane in an adequate 2 : 1 stoichiometry. Compound 2 shows a boat-tweezer conformation that makes it ideal for being used as a host in molecular recognition processes. Different polyaromatic hydrocarbons (PAHs) and polyfluorinated compounds (PFCs) have been used as guests and a stronger interaction has been detected for PAHs, especially for anthracene, in agreement with spectrofluorometric titrations and the calculated values of the association constants, which is confirmed by DFT calculations. Compound 2 has then been immobilized in different organic matrices, in order to enhance room temperature phosphorescence (RTP). This promotes sensing with dual emission and furthermore in the case of the analytes under investigation, phosphorescence is observed in a range of wavelengths that do not coincide with the fluorescence emission of PAHs and PFCs. [ABSTRACT FROM AUTHOR]

Treatment of N‐methyl‐S,S‐diaryl sulfoximines with methyl trifluoromethanesulfonate provides bench‐stable sulfoxinium salts in excellent yields. Applying them in Sonogashira‐, Heck‐ and Suzuki‐type cross‐coupling reactions leads to the corresponding products by sequential C−S bond cleavage and C−C bond formation. Electronic factors induced by substituents on the S‐aryl groups govern the coupling efficiency. [ABSTRACT FROM AUTHOR]

The synthesis of iodine(I) complexes with either benzoimidazole or carbazole‐derived sp2N‐containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two‐coordinate Ag(I) complexes produces iodine(I) complexes with a three‐center four‐electron (3c–4e) [N−I−N]+ bond. The 1H and 1H‐15N HMBC NMR studies unambiguously confirm the formation of the complexes in all cases via the [N−Ag−N]+→[N−I−N]+ cation exchange, with the 15N NMR chemical shift change between 94 to 111 ppm when compared to the free ligand. The single crystal X‐ray crystallographic studies on eight I+ complexes revealed highly symmetrical [N−I−N]+ bonds with I−N bond distances of 2.21–2.26 Å and N−I−N angles of 177–180°, whilst some of the corresponding Ag+ complexes showed a clear deviation from linearity with N−Ag−N angles of ca. 150° and Ag−N bond distances of 2.09–2.18 Å. [ABSTRACT FROM AUTHOR]

Six bile acid alkyl amide derivatives were studied with respect to their gelation properties. The derivatives were composed of three different bile acids with hexyl or cyclohexyl side chains. The gelation behaviour of all six compounds were studied for 36 solvents with varying polarities. Gelation was observed mainly in aromatic solvents, which is characteristic for bile‐acid‐based low molecular weight gelators. Out of 108 bile acid‐solvent combinations, a total of 44 gel systems were formed, 28 of which from lithocholic acid derivatives, only two from deoxycholic acid derivatives, and 14 from cholic acid derivatives. The majority of the gel systems were formed from bile acids with hexyl side chains, contrary to the cyclohexyl group, which seems to be a poor gelation moiety. These results indicate that the spatial demand of the side chain is the key feature for the gelation properties of the bile acid amides. [ABSTRACT FROM AUTHOR]

Neutral halogen‐bonded O−I−N complexes were prepared from in situ formed carbonyl hypoiodites and aromatic organic bases. The carbonyl hypoiodites have a strongly polarized iodine atom with larger σ‐holes than any known uncharged halogen bond donor. Modulating the Lewis basicity of the selected pyridine derivatives and carboxylates leads to halogen‐bonded complexes where the classical O−I⋅⋅⋅N halogen bond transforms more into a halogen‐bonded COO−⋅⋅⋅I−N+ ion‐pair (salt) with an asymmetric O−I−N moiety. X‐ray analyses, NMR studies, and calculations reveal the halogen bonding geometries of the carbonyl hypoiodite‐based O−I−N complexes, confirming that in the solid‐state the iodine atom is much closer to the N‐atom of the pyridine derivatives than its original position at the carboxylate O‐atom. [ABSTRACT FROM AUTHOR]

A series of compressed M[Li313Ti2] (M = Li, Na, K, Rb, Cs) and expanded helicates M4[13Ti2] has been obtained. The helicates Li3[M13Ti2] or M4[13Ti2] with M = Na+, K+, Rb+, or Cs+ adopt the expanded structure in solution. By crystallization the compressed structures M[Li313Ti2] (M = Na, Rb) are obtained. This represents an example of cation-translocation based isomerism. [ABSTRACT FROM AUTHOR]

By visible‐light photoredox catalysis with copper complexes, sulfoximidoyl chlorides add to terminal aryl alkynes to give the corresponding (E)‐β‐chlorovinyl sulfoximines with exclusive regio‐ and stereoselectivities in high yields. Two representative products have been characterized by X‐ray crystal structure analysis. Radicals appear to be decisive intermediates. As demonstrated by two subsequent reactions, the products can be derivatized. [ABSTRACT FROM AUTHOR]

The synthesis of four novel gold(I)-phosphane complexes coordinated to 9-phenanthrene chromophore has been carried out through the reaction of 9-phenanthreneboronic acid and the corresponding AuClPR3 (PR3 = PPh3 for triphenylphosphane (1a); 1,4-bis(diphenylphosphanyl)butane or dppb (2b); bis(diphenylphosphanyl)acetylene or dppa (2c); (AuCl)2(diphos) (diphos = bis(diphenylphosphanyl)methane or dppm (3)) sources. The X-ray crystal structures of compounds 1a and 2b show the existence of MOF-like intermolecular assemblies that contain empty inner cavities in the absence of aurophilic contacts. In contrast, the formation of a tetranuclear complex with intramolecular aurophilic interactions was evidenced for 3. Photophysical characterization indicates dual emission in all gold(I) complexes when oxygen is removed from the sample, while only fluorescence emission is recorded for the uncoordinated ligand. The introduction of the compounds within PMMA and Zeonex was assayed, and luminescent films containing gold(I) complexes where phosphorescence is the sole pathway for emission are obtained, instead of the dual emission (with significant fluorescence contribution) recorded in solution. [ABSTRACT FROM AUTHOR]

Three‐dimensional aza‐analogues of 1,2‐benzothiazine 1,1‐dioxides have been prepared from sulfonimidamides. Two different protocols are presented. The first is a rhodium‐catalyzed annulation reaction with α‐sulfonyloxyketones leading to 4‐unsubstituted benzothiazine derivatives. By selective bromination with NBS the heterocyclic ring can further be functionalized. In the second approach, an iridium catalyst is applied under solvent‐free mechanochemical conditions providing products with 3,4‐disubstituted thiazine rings from diazoketo esters and diazoketo sulfones. [ABSTRACT FROM AUTHOR]

Involving the cyano group of N‐cyano sulfoximines in [3+2]‐cycloaddition reactions with 1,3‐dipoles provides practical routes for the construction of 5‐membered heterocycles bearing sulfoximinoyl moieties. An ytterbium‐catalyzed cycloaddition utilizing hydrazonoyl chlorides was developed, as well as a reaction involving imidoyl chlorides proceeding without the aid of a catalyst. Following these protocols, a range of sulfoximines with N‐1,2,4‐triazolyl and N‐1,2,4‐oxadiazolyl substituents was prepared. [ABSTRACT FROM AUTHOR]

Facile α‐H elimination from tetrakis(trimethylsilylmethyl)titanium precursors to give adducts of (alkylidene)bis(alkyl)titanium complexes is induced by light alkali metal amides of the NNNN‐type macrocyclic anionic ligand Me3TACD [(Me3TACD)H=1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane]. In the crystal, the alkali metal interacts with the carbene carbon atom or with the CH2 group of the trimethylsilymethyl ligand. The nucleophilic character of the carbene carbon atom was shown by the reaction with benzophenone and terminal acetylenes. Facile α‐H elimination from tetrakis(trimethylsilylmethyl)titanium is induced by alkali metal amides to give adducts of (alkylidene)bis(alkyl)titanium complexes. In the crystal, the alkali metal interacts with the carbene carbon atom or with the CH2 group of the trimethylsilymethyl ligand. The nucleophilic character of the carbene carbon atom was shown by reactions with benzophenone and terminal acetylenes. [ABSTRACT FROM AUTHOR]

Die α‐H‐Eliminierung in Tetrakis(trimethylsilylmethyl)titan‐Vorstufen unter Bildung von (Alkyliden)bis(alkyl)titan‐Komplexen wird durch Metallamide leichter Alkalimetalle mit makrozyklischen Liganden Me3TACD [(Me3TACD)H=1,4,7‐Trimethyl‐1,4,7,10‐tetraazacyclododecan] vom NNNN‐Typ hervorgerufen. Im Kristall wechselwirkt das Alkalimetall mit dem Carben‐Kohlenstoffatom oder der CH2‐Gruppe des Trimethylsilymethylliganden. Der nukleophile Charakter des Carben‐Kohlenstoffatoms wurde durch die Reaktionen mit Benzophenon und mit terminalen Acetylenen gezeigt. Eine leichte α‐H‐Eliminierung in Tetrakis(trimethylsilylmethyl)titan durch Alkalimetallamide mit makrozyklischen Me3TACD‐Liganden führt zu (Alkyliden)bis(alkyl)titan‐Komplexaddukten. Im Kristall wechselwirkt das Alkalimetall mit dem Carben‐C‐Atom oder der CH2‐Gruppe des Trimethylsilymethylliganden. Der nukleophile Charakter des Carben‐C‐Atoms wurde durch Reaktionen mit Benzophenon und terminalen Acetylenen demonstriert. [ABSTRACT FROM AUTHOR]

The substituted acetylacetone 3‐[2‐(pyridin‐4‐yl)ethyl]pentane‐2,4‐dione, C12H15NO2, (1), with an ethylene bridge between the acetylacetone moiety and the heteroaromatic ring, represents an attractive linker for mixed‐metal coordination polymers. In the crystal, (1) adopts an antiperiplanar conformation with respect to the C—C bond in the central ethylene group and almost coplanar acetylacetone and pyridyl groups. The ditopic molecule exists as the enol tautomer, with proton disorder in the short intramolecular hydrogen bond. Single‐crystal neutron diffraction at 2.5 K indicated site occupancies of 0.602 (17) and 0.398 (17). The geometry of the acetylacetone moiety is in agreement with such a site preference of the bridging hydrogen: the O atom associated with the preferred H‐atom site subtends the longer [1.305 (2) Å] and the more carbonyl‐like O atom the shorter [1.288 (2) Å] C—O bond. Based on structure‐factor calculations for the alternative H‐atom sites, reflections particularly sensitive for proton distribution were identified and measured in a second neutron data collection at 170 K. At this temperature, 546 independent neutron intensities were used to refine positional and isotropic displacement parameters for a structure model in which parameters for C and O atoms were constrained to those obtained by single‐crystal X‐ray diffraction at the same temperature. The site occupancies for the disordered proton do not significantly differ from those at 2.5 K. Single‐crystal neutron diffraction at 2.5 K and a subset of neutron data collected at 170 K, combined with information from X‐ray diffraction at the same temperature, suggest static disorder for the proton in the short intramolecular hydrogen bond of 3‐[2‐(pyridin‐4‐yl)ethyl]pentane‐2,4‐dione. [ABSTRACT FROM AUTHOR]

Bis(triphenylsilyl) and dibenzyl ytterbium(ii) complexes supported by the macrocyclic polyamine ligand Me4TACD (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) reacted with H2 to give the cationic ytterbium hydrides [(Me4TACD)2Yb2(μ2-H)(2+n)](2−n)+ (n = 0, 1). The hydrides catalyzed the H2/D2 isotope exchange as well as hydrogenation and hydrosilylation of 1-hexene. [ABSTRACT FROM AUTHOR]

A series of [(PMP)Rh(CO)Cl]n+ complexes was synthesised and the impact of the metalloligands CuI, LiI and ZnII on the CO stretching band was analysed. [ABSTRACT FROM AUTHOR]

Abstract: The application of our newly developed B–C coupling method by catalytic Si/B exchange is demonstrated for the synthesis of a series of triarylboranes (1), monodisperse thienyl‐ and furylborane dimers (2) and trimers (9), extended oligomers (3) and polymers (3′), as well as mixed (oligo)thienyl‐/furylboranes. The structures of 1 aaTip, 1 bbTip, and 2 bbbMes*, determined by X‐ray crystallography, reveal largely coplanar hetarene rings and BR3 environments, which are most pronounced in the furylborane species. Photophysical investigations, supported by TD‐DFT calculations, revealed pronounced π‐electron delocalization over the hetarene backbones including the boron centers. With an extended series of derivatives of varying chain lengths available, we were able to determine the effective conjugation lengths (ECL) of poly(thienylborane)s and poly(furylborane)s, which have been reached with the highest‐molecular‐weight derivatives of our study. Through variation of the furan‐to‐thiophene ratio, the photophysical properties of these materials are effectively modulated. Significantly, higher furan contents lead to considerably increased fluorescence intensities. Compounds 1 aaTip, 1 bbTip, and 3 aTip showed the ability to bind fluoride anions. The binding process is signaled by a distinct change in their optical absorption characteristics, thus rendering these materials attractive targets for sensory applications. [ABSTRACT FROM AUTHOR]

A series of light alkali metal organoperoxides [MOOR] (M=Li, Na, K; R= tBu, CMe2Ph) were isolated in mononuclear form, aided by the tetradentate and neutral NNNN-type macrocycle Me4TACD (L; Me4[12]aneN4=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) and strong hydrogen bonds from additional ROOH molecules. The Na and K compounds are characterized by short O−H⋅⋅⋅O contacts, in the case of the Na derivative as short as 2.41 Å. [ABSTRACT FROM AUTHOR]

Single-crystal neutron diffraction experiments at 100 and 2.5 K have been performed to determine the structure of 3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to its protonation pattern and to monitor a low-temperature phase transition. Solid HacacPy exists as the enol tautomer with a short intramolecular hydrogen bond. At 100 K, its donor···acceptor distance is 2.450 (8) Å and the compound adopts space group C2/ c, with the N and para-C atoms of the pyridyl ring and the central C of the acetylacetone substituent on the twofold crystallographic axis. As a consequence of the axial symmetry, the bridging hydrogen is disordered over two symmetrically equivalent positions, and the carbon-oxygen bond distances adopt intermediate values between single and double bonds. Upon cooling, a structural phase transition to the t2 subgroup P occurs; the resulting twins show an ordered acetylacetone moiety. The phase transition is fully reversible but associated with an appreciable hysteresis in the large single crystal under study: transition to the low-temperature phase requires several hours at 2.5 K and heating to 80 K is required to revert the transformation. No significant hysteresis is observed in a powder sample, in agreement with the second-order nature of the phase transition. [ABSTRACT FROM AUTHOR]

We herein showcase the ability of NHC-coordinated dinuclear NiI-NiI complexes to override fundamental reactivity limits of mononuclear (NHC)Ni0 catalysts in cross-couplings. This is demonstrated with the development of a chemoselective trifluoromethylselenolation of aryl iodides catalyzed by a NiI dimer. A novel SeCF3-bridged NiI dimer was isolated and shown to selectively react with Ar−I bonds. Our computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive. [ABSTRACT FROM AUTHOR]

The ditopic organic molecule 3-(pyridin-4-yl)acetylacetone (HacacPy) acts as a pyridine-type ligand towards Hg X2 ( X = Cl, Br, I). The nature of the anion and the ligand-to-cation ratio dominate the outcome of the reaction. Two different coordination compounds form with HgCl2, namely a ligand-rich mononuclear complex, HgCl2(HacacPy)2, and a ligand-deficient one-dimensional chain polymer, [Hg( μ-Cl)2(HacacPy)]1∞, with five-coordinated HgII cations. Two compounds are also observed for HgBr2, a molecular complex isomorphous to the chloride derivative and a chain polymer with the composition [Hg( μ-Br)Br(HacacPy)]1∞, in which the cations are four-coordinated. The ligand-rich mononuclear and ligand-deficient polymeric chloride and bromide complexes may be interconverted via thermal degradation and mechanochemical synthesis. In contrast to the chloride and bromide compounds, the reaction product with HgI2 does not depend on the ligand-to-cation ratio but corresponds to [Hg( μ-I)I(HacacPy)]1∞, isomorphous to the bromide derivative. The N-coordinated HacacPy complexes could not be deprotonated and further crosslinked with a second cation. Synthesis of mixed-metal products could be achieved, however, by deprotonation of the acetylacetone moiety in HacacPy and formation of tris-chelated Fe(acacPy)3 and Al(acacPy)3 complexes in the first step. These mononuclear building blocks act as bridging poly(pyridine) ligands towards HgII halides and form two structure types. The first represents a one-dimensional ladder, with the tris(ligand) complexes acting as triconnected nodes and the HgII halides acting as linkers. In the alternative unprecedented product, both the tris(ligand) complexes and the [Hg X2( μ- X)Hg X] groups act as equivalent triconnected nodes. They form a uninodal two-dimensional coordination network with vertex symbol 4.82 and fes topology. [ABSTRACT FROM AUTHOR]

3-(Pyridin-4-yl)acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdII and HgII halides. With CdBr2, the one-dimensional polymer [Cd(μ-Br)2(HacacPy)Cd(μ-Br)2(HacacPy)2]∞ is obtained in which five- and six-coordinated CdII cations alternate in the chain direction. Reaction of HacacPy with HgBr2 results in [Hg(μ-Br)Br(HacacPy)]∞, a polymer in which each HgII centre is tetracoordinated. In both compounds, each metal(II) cation is N-coordinated by at least one HacacPy ligand. Equimolar reaction between these CdII and HgII derivatives, either conducted in ethanol as solvent or via grinding in the solid state, leads to ligand redistribution and the formation of the well-ordered bimetallic polymer catena-poly[[bromidomercury(II)]-μ-bromido-[aquabis[4-hydroxy-3-(pyridin-4-yl)pent-3-en-2-one]cadmium(II)]-di-μ-bromido], [CdHgBr4(C10H11NO2)2(H2O)] n or [{HgBr}(μ-Br){(HacacPy)2Cd(H2O)}(μ-Br)2]∞. HgII and CdII cations alternate in the [100] direction. The HacacPy ligands do not bind to the HgII cations, which are tetracoordinated by three bridging and one terminal bromide ligand. The CdII centres adopt an only slightly distorted octahedral coordination. Three bromide ligands link them in a (2 + 1) pattern to neighbouring HgII atoms; two HacacPy ligands in a cis configuration, acting as N-atom donors, and a terminal aqua ligand complete the coordination sphere. Classical O-H...Br hydrogen bonds stabilize the polymeric chain. O-H...O hydrogen bonds between aqua H atoms and the uncoordinated carbonyl group of an HacacPy ligand in a neighbouring strand in the c direction link the chains into layers in the (010) plane. [ABSTRACT FROM AUTHOR]

Depending on the reaction partner, the organic ditopic molecule isonicotinic acid (Hina) can act either as a Brønsted acid or base. With sulfuric acid, the pyridine ring is protonated to become a pyridinium cation. Crystallization from ethanol affords the title compound tris(4-carboxypyridinium) hydrogensulfate sulfate monohydrate, 3C6H6NO2+·HSO4−·SO42−·H2O or [(H2ina)3(HSO4)(SO4)(H2O)]. This solid contains 11 classical hydrogen bonds of very different flavour and nonclassical C-H...O contacts. All N-H and O-H donors find at least one acceptor within a suitable distance range, with one of the three pyridinium H atoms engaged in bifurcated N-H...O hydrogen bonds. The shortest hydrogen-bonding O...O distance is subtended by hydrogensulfate and sulfate anions, viz. 2.4752 (19) Å, and represents one of the shortest hydrogen bonds ever reported between these residues. [ABSTRACT FROM AUTHOR]

Molecular aluminum hydride [(L)AlH2] (L = Me3TACD) reacted with 2 equiv. of BPh3 in THF or THP to give the cationic alkoxides [(L)Al(OR)][HBPh3] (R = nBu, nPent) by facile ring-opening of the cyclic ethers. The Cα–O bond cleavage which involves the isolable intermediate [(L)AlH][HBPh3] is a result of hydride transfer to Cα from [HBPh3]−. [ABSTRACT FROM AUTHOR]

In recent years, the studies of RNA and its use for the development of RNA based vaccines have increased drastically. Although cyanine dyes are commonly used probes for studying nucleic acids, in a wide range of applications, there is still a growing need for better and brighter dyes. To meet this demand, we have systematically studied the structure of SYBR green-related cyanine dyes to gain a deeper understanding of their interactions with biomolecules especially how they interact with nucleic acids and the structural components which makes them strongly fluorescent. Herein, five new dyes were synthesized, and their photophysical properties were evaluated. Observations of photophysical characteristics were compared to calculations by using density functional theory in its ground state and time-dependent form to model the optical absorption spectra and excited state properties of the selected molecules. Single crystal X-ray crystal structures of five cyanine dyes were determined and the interactions of the cyanine dye-DNA complex were studied by using molecular docking and molecular dynamics calculations. Three molecular structural features were discovered: a) removing the benzene ring from the thiazolium moiety of the dye lowers the fluorescence drastically, and that the quantum yield can be enhanced, therefore increasing the fluorescence, by b) incorporating methanethiol substituent at the quinoline moiety instead of dimethylamine or c) changing the thiazolium moiety to an oxazolium moiety. [Display omitted] • Five new cyanine dyes were synthesized. • The main characteristics that affect the fluorescence of the dyes were recognized. • Up to 1050 times fluorescence enhancement was observed. • X-ray crystal structures of five cyanine dyes were solved. • MD calculations suggested that studied dyes bind with the AT-rich minor groove of dsDNA. [ABSTRACT FROM AUTHOR]

3-(4-Pyridyl)-acetylacetone (HacacPy) acts as a pyridine-type ligand towards Cd X2 ( X = Cl, Br, I). Chain polymers with six-coordinated metal cations are obtained from CdCl2 and with alternating five- and six-coordinated Cd centers from CdBr2. In either case, the formation of these compounds does not depend on the precise stoichiometry. In contrast, two different reaction products form with the heavier congener CdI2, namely a ligand-rich molecular complex CdI2(HacacPy)2 and a ligand-deficient one-dimensional polymer [CdI2(HacacPy)]1∞. Interconversion between these two iodo derivatives is possible via thermal degradation and mechanochemical synthesis. The acetylacetone moiety in HacacPy may be deprotonated and chelated to FeIII, and the resulting complex Fe(acacPy)3 reacts analogously to a bridging polypyridine ligand towards the same Cd halides as the molecule HacacPy itself. With CdCl2 and CdBr2, isomorphous chain polymers are obtained in which the Cd cations adopt distorted octahedral coordination and one of the peripheric pyridyl groups remains uncoordinated. With CdI2, the iron complex acts as a -Fe(acacPy)3 bridge between tetrahedral Cd centers and gives rise to a ladder structure. [ABSTRACT FROM AUTHOR]

Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto's catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto's catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their supramolecular binding to a series of zinc porphyrins was studied with UV-Vis and circular dichroism (CD) spectroscopy, computational analysis and single crystal X-ray diffraction. The association constant values generally increased with the increasing electron-withdrawing properties of the porphyrins and electron-donating ability of the thioureas, a result of the predominant Zn ⋯ N cation–dipole (Lewis acid–base) interaction. The binding event induced a CD signal in the Soret band region of the porphyrin hosts—a crucial property for chirality sensing of Takemoto-type thioureas. [ABSTRACT FROM AUTHOR]