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Single-ion magnet (SIM) requires large magnetic moment and strong magnetic anisotropy, which are beneficial to the large energy barrier of magnetization reorientation and accordingly high blocking temperature. Much effort has...

A monovalent (Non-Gomberg type) germanium radical 1 stabilized by phenalenyl-based bidentate ligand was synthe-sized. Because of the high thermal stability originating from spin delocalization over the phenalenyl moiety, it was possi-ble to isolate compound 1 in crystalline form by sublimation at ca. 300 °C. ESR spectra, crystallographic analysis, theo-retical calculations, and reactivities with carbon radicals suggest that the spin of 1 is distributed on the phenalenyl moie-ty, while 1 behaves as a germanium-centered radical in its reactions with C2Cl6, PhSSPh, and p-benzoquinone to form Ge−E (E = Cl, S, O) bonds.

Reactions of Pd8 strings supported by meso-Ph2 PCH2 P(Ph)CH2 P(Ph)CH2 PPh2 (meso-dpmppm) ligands, [Pd8 (meso-dpmppm)4 (L)2 ]4+ (L=CH3 CN (1), XylNC (2)) with C60 resulted in the exclusive formation of unprecedented metal-chain-wired C60 bucky balls, [{Pd4 (meso-dpmppm)2 (L)}2 (C60 )]4+ (L=CH3 CN (11), XylNC (12)), in which a C60 fullerene is trapped in the central Pd-Pd junction, as unambiguously established by spectroscopic, X-ray crystallographic, and theoretical techniques. The similar reaction of Pd8 strings supported by rac-dpmppm, [Pd8 (rac-dpmppm)4 (CH3 CN)2 ]4+ (3) also afforded a racemic mixture of [{Pd4 ((R*,R*)-dpmppm)2 (CH3 CN)}2 (C60 )]4+ (13) without scrambling the Pd4 fragments with (R,R)- and (S,S)-dpmppm ligands. Consequently, those of enantiopure chiral Pd8 strings, [Pd8 ((R*,R*)-dpmppm)4 (CH3 CN)2 ]4+ , certainly afforded chiral bucky balls of [{Pd4 ((R*,R*)-dpmppm)2 (CH3 CN)}2 (C60 )]4+ (13RR and 13SS ), that exhibit mirror-image circular dichroism spectra. The reactions of 1 and 2 were also applied for trapping a C70 fullerene to give 2 : 1 adducts of [{Pd4 (meso-dpmppm)2 (L)}2 (C70 )]4+ (L=CH3 CN (21), XylNC (22)). These results provide useful information for creating a platform to develop dimensionally and chirality controlled metal-carbon nanocomposite materials.

Ferroelectric spin crossover (SCO) behavior is demonstrated to occur in the cobalt(II) complex, [Co(FPh-terpy)2 ](BPh4 )2 ⋅3ac (1⋅3 ac; FPh-terpy=4'-((3-fluorophenyl)ethynyl)-2,2':6',2''-terpyridine) and is dependent on the degree of 180° flip-flop motion of the ligand's polar fluorophenyl ring. Single crystal X-ray structures at several temperatures confirmed the flip-flop motion of fluorobenzene ring and also gave evidence for the SCO behavior with the latter behavior also confirmed by magnetic susceptibility measurements. The molecular motion of the fluorobenzene ring was also revealed using solid-state 19 F NMR spectroscopy. Thus the SCO behavior is accompanied by the flip-flop motion of the fluorobenzene ring, leading to destabilization of the low spin cobalt(II) state; with the magnitude of rotation able to be controlled by an electric field. This first example of spin-state conversion being dependent on the molecular motion of a ligand-appended fluorobenzene ring in a SCO cobalt(II) compound provides new insight for the design of a new category of molecule-based magnetoelectric materials.

The redox reaction pathway of silver nanocluster formation in the polyol method is investigated by density functional theory calculation. It is suggested that the formation of Ag2(0) cluster with s...

A hetero-dinuclear IrIII–CuII complex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate in water. An IrIII–H intermediate, generated through formate dehydrogenation, was revealed to activate terminal aromatic olefins to afford an Ir-alkyl species, and the process was promoted by a hydrophobic [IrIII–H]-[substrate aromatic ring] interaction in water. The Ir-alkyl species subsequently reacted with dioxygen to yield corresponding methyl ketones and was promoted by the presence of the CuII moiety under acidic conditions. The IrIII–CuII complex exhibited cooperative catalysis in the selective aerobic oxidation of olefins to corresponding methyl ketones, as evidenced by no reactivities observed from the corresponding mononuclear IrIII and CuII complexes, as the individual components of the IrIII–CuII complex. The reaction mechanism afforded by the IrIII–CuII complex in the aerobic oxidation was disclosed by a combination of spectroscopic detection of reaction intermediates, kinetic analysis, and theoretical calculations., A hetero-dinuclear IrIII–CuII complex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate and promoted by a hydrophobic interaction in water.

Binuclear Pd(II) and Pt(II) complexes supported by rac-dpmppm (bis[(diphenylphosphinomethyl)phenylphosphino]methane) in a triply-bridged Z-form, [M2Cl4(rac-dpmppm)] (M = Pd (3a), Pt (3b)), readily reacted with 2,6-xylyl isocyanide (XylNC) in the presence of NH4PF6 to afford [M2Cl2(rac-dpmppm)(XylNC)2](PF6)2 (M = Pd (4a), Pt (4b)), in which each metal center accommodates one isocyanide ligand at the trans position to the inner P atom of dpmppm. Similarly, treatment of 3a and 3b with axially chiral (R/S)-1,1'-binaphthyl-2,2'-bisisocyanide (rac-Binac) in the presence of NH4OTf gave cyclic tetranuclear complexes, [{M2Cl2(rac-dpmppm)(rac-Binac)}2](OTf)4 (M = Pd (5), Pt (8)), where two {M2Cl2(rac-dpmppm)}2+ fragments are connected by two rac-Binac ligands through chirality sorting of (R*,R*)-dpmppm and (R*)-Binac. Complex 5 could be transformed into the halide exchanged tetranuclear complexes, [{Pd2X2(rac-dpmppm)(rac-Binac)}2](OTf)4 (X = Br (6), I (7)), to show that the rectangular arrangement of four Pd(II) ions is elongated by repulsive interaction between halide ligands. By using (R)- and (S)-Binac, enantiopure Pd4 complexes, [{Pd2Cl2((R*,R*)-dpmppm)((R*)-Binac)}2](OTf)4 (5RR/R and 5SS/S), were successfully isolated as pure crystalline forms, from which enantiopure (R,R)- and (S,S)-dpmppm were obtained by treatment with NaCN aqueous solution. Namely, optical resolution of rac-dpmppm was established through the tetranuclear Pd complexes, which is the first example for methylene-bridged polyphosphines, R2P(CH2PR)nCH2PR2 (n > 0). Furthermore, chiral octapalladium chains, [Pd8((R*,R*)-dpmppm)4(N≡CCH3)2](BF4)4 (2RR and 2SS), were synthesized by reacting enantiopure P-chiral dpmppm with [Pd2(CH3CN)6](BF4)2 and [Pd2(dba)3]·C6H6 and were characterized by spectroscopic and X-ray crystallographic analyses, to determine the absolute configurational structures. The Pd8 chains are the longest enantiopure chiral single-metal-atom chains structurally characterized, thus far, and the electronic structures were examined on the basis of DFT calculations of 2RR.

Density functional theory calculations with plane-wave basis sets are often used for theoretical investigations of solid materials; nevertheless, analysis techniques for open shell structures are i...

With adequate building blocks, metal–organic frameworks (MOFs) can combine magnetic ordering and porosity. This makes MOFs a promising platform for the development of stimuli-responsive materials that show drastically different magnetic properties depending on the presence or absence of guest molecules within their pores. Here we report a CO2-responsive magnetic MOF that converts from ferrimagnetic to paramagnetic on CO2 adsorption, and returns to the ferrimagnetic state on CO2 desorption. The ferrimagnetic material is a layered MOF with a [D+–A−–D] formula, produced from the reaction of trifluorobenzoate-bridged paddlewheel-type diruthenium(ii) clusters as the electron donor (D) with diethoxytetracyanoquinodimethane as the electron acceptor (A). On CO2 uptake, it undergoes an in-plane electron transfer and a structural transition to adopt a [D–A–D] paramagnetic form. This magnetic phase change, and the accompanying modifications to the electronic conductivity and permittivity of the MOF, are electronically stabilized by the guest CO2 molecules accommodated in the framework. Metal–organic frameworks (MOFs) can combine porosity and magnetic order within their lattice, which makes them attractive for the development of stimuli-responsive magnets. Now, a MOF has been prepared that converts from a ferrimagnet to a paramagnet with CO2 uptake, and returns to the ferrimagnetic state on releasing CO2.

Recently, mixed-metal metal–organic frameworks (MOFs) have been attracting much attention in various fields. In this study, we have systematically investigated the magnetic properties of CoxNi₁–x-MOF-74 [Co₂xNi₂(₁–x)(dhtp), where H₄dhtp = 2, 5-dihydroxyterephthalic acid] with two different kinds of metals (Co and Ni) across the composition range 0 ≤ x ≤ 1. Bimetallic CoxNi₁–x-MOF-74 (x = 0.752, 0.458, and 0.233) were successfully synthesized and confirmed to have homogeneous metal distributions. Weak ferromagnetic (canted antiferromagnetic) behavior was exhibited, while homometallic Co-MOF-74 and Ni-MOF-74 are antiferromagnetic. We also investigated the effects of C₂H₄ sorption on the magnetic properties and found that C₂H₄-adsorbed Co₀.₅Ni₀.₅-MOF-74 exhibited a change in the interchain magnetic interaction.

Hexaazatriphenylene (HAT) derivatives have attracted wide attention because of their electron-deficient nature and unique self-assembly properties. In this work, a facile synthesis method for obtaining HAT derivatives with alternating electron-withdrawing nitrile and electron-donating alkoxy groups (HATCNOCn) is proposed. Crystal structure analysis indicated that HATCNOCn forms a one-dimensional columnar structure via strong π-π interactions. Density functional theory calculations revealed that the edge of HATCNOCn is divided into positively and negatively charged sites owing to the presence of alternating nitrile and alkoxy groups, which would induce strong π-π interactions. Thermal analysis and polarizing optical microscopy revealed that HATCNOCn exhibits columnar liquid-crystal phases. Time-resolved microwave conductivity measurements further demonstrated the photoconductive nature of HATCNOCn. The proposed strategy could provide a new strategy for the design of novel organic semiconductive materials.

Host-guest electron transfer (HGET) in molecular framework systems is a critical trigger for drastic functional changes in both host framework and guest. A reversible magnetic phase transition was achieved via HGET in a layered framework, [{Ru

A rational strategy for constructing a packing structure with diffusion paths for lithium ions is a critical requirement in the development of organic cathode active materials. Charge-transfer (CT)...

Chemical indices are effective tools for examining the functions and reactivities of stable radical species. In this study, we formulated an approximation to estimate chemical indices using electron density. Theoretical investigations using the developed scheme revealed that surface interactions can tune chemical indices and that the diradical character was enhanced by weak adsorption onto ionic solids with charge–dipole interactions.

The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster.

The effect of periodic structure on the effective exchange integral (Jab) was investigated using density functional theory calculations with plane-wave basis and approximate spin projection scheme ...

A new design strategy for high-performance organic cathode active materials for lithium-ion batteries is presented, which involves the assembly of redox-active organic molecules with a crystalline porous structure using mixed-stacked charge-transfer (CT) complexes. Hexahydroxytriphenylene was used as a donor molecule and 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile as an acceptor molecule to give a new porous CT complex (PCT-1) with a pseudo-hexagonal mixed columnar structure. X-ray diffraction measurements and sorption experiments demonstrated that the intercolumnar spaces in PCT-1 can incorporate various molecules accompanied by lattice expansion. A lithium metal battery containing PCT-1 as a cathode active material exhibited a high capacity of 288 mA h g−1 at 500 mA g−1, and this performance was attributed to a combination of the redox-active units and the porous structure of PCT-1.

Efficient detoxification of harmful benzene rings into useful carboxylic acids in water is indispensable for achieving a clean water environment. We report herein that oxidative aromatic cracking (OAC) reactions in water were achieved using a catalytic system with a cobalt-substituted Keggin-type polyoxometalate (Co-POM) as a catalyst, an Oxone® monopersulfate compound as a sacrificial oxidant and sodium bicarbonate as an additive under mild conditions. Sodium bicarbonate plays a crucial role in the selective OAC reactions by Co-POM using ethylbenzenesulfonate as a model substrate. The reactive species was characterized to be a cobalt(III)-oxyl species based on 31P NMR, UV-vis spectroscopic, kinetic, and theoretical analyses. The electrophilicity of the cobalt(III)-oxyl species was demonstrated by a linear relationship with a negative slope in the Hammett plots of initial rates obtained from the OAC reactions of m-xylenesulfonate derivatives. Besides, we have verified the degradation pathway of the OAC reactions using benzene as a model substrate in the catalytic system. The degradation was initiated by an electrophilic attack of the cobalt(III)-oxyl species on benzene to yield phenol followed by producing catechol, muconic acid, maleic/fumaric acid, tartaric acid derivatives and formic acid on the basis of 1H NMR spectroscopic analysis.

By using a linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), nona- and hexadecanuclear copper hydride clusters, [Cu9 H7 (μ-dpmppm)3 ]X2 (X=Cl (1 a), Br (1 b), I (1 c), PF6 (1 d)) and [Cu16 H14 (μ-dpmppm)4 ]X2 (X2 =I2 (2 c), (4/3) PF6 ⋅(2/3) OH (2 d)) were synthesized and characterized. They form copper-hydride cages of apex-truncated supertetrahedral {Cu9 H7 }2+ and square-face-capped cuboctahedral {Cu16 H14 }2+ structures. The hydride positions were estimated by DFT calculations to be facially dispersed around the copper frameworks. A kinetically controlled synthesis gave an unsymmetrical Cu8 H6 cluster, [Cu8 H6 (μ-dpmppm)3 ]2+ (3), which readily reacted with CO2 to afford linear Cu4 complexes with formate bridges, leading to an unprecedented hydrogenation of CO2 into formate catalyzed by {Cu4 (μ-dpmppm)2 } platform. The results demonstrate that new motifs of copper hydride clusters could be established by the tetraphosphine ligands, and the structures influence their reactivity.

The electron-donor(D) and -acceptor(A)-assembled D2 A-layer framework [{Ru2 (m-FPhCO2 )4 }2 TCNQ(OMe)2 ]⋅nDCE (1-nDCE; m-FPhCO2- =m-fluorobenzoate; TCNQ(OMe)2 =2,5-dimethoxyl-7,7,8,8-tetracyanoquinodimethane; DCE=1,2-dichloroethane) undergoes drastic charge-ordered state variations via three distinct states that are a two-electron-transferred state (2e-I), a charge-disproportionated state (1.5e-I), and a one-electron-transferred state (1e-I), depending on the degree of solvation by nDCE. The pristine form 1-4DCE has a paramagnetic 2e-I state, which eventually produces the solvent-free form 1 in 1.5e-I via an intermediate state 1-nDCE (n≤1) in 1e-I. Resolvation of 1 stabilizes 1-DCE, allowing it to switch between 1.5e-I and 1e-I, and to become ferrimagnetic with a Tc of 30 K (1.5e-I) and 88 K (1e-I). The stabilization of the 1e-I state of 1-DCE is due to the presence of host-guest hydrogen bonding that enables to suppress the electron-donation ability of D even in an identical framework with 1.

A series of the octapalladium chains supported by meso-Ph2 PCH2 P(Ph)CH2 P(Ph)CH2 PPh2 (meso-dpmppm) ligands, [Pd8 (meso-dpmppm)4 (L)2 ](BF4 )4 (L=none (1), solvents: CH3 CN (2 a), dmf (2 b), dmso (2 c), RN≡C: R=Xyl (3 a), Mes (3 b), Dip (3 c), t Bu (3 d), Cy (3 e), CH3 (CH2 )7 (3 f), CH3 (CH2 )11 (3 g), CH3 (CH2 )17 (3 h)) and [Pd8 (meso-dpmppm)4 (X)2 ](BF4 )2 (X=Cl (4 a), N3 (4 b), CN (4 c), SCN (4 d)), were synthesized by using 2 a as a stable good precursor, and characterized by spectroscopic (IR, 1 H and 31 P NMR, UV-vis-NIR, ESI-MS) measurements and X-ray crystallographic analyses (for 1, 2 a, b, 3 a, b, e, f, 4 a-d). On the basis of DFT calculations on the X-ray determined structure of 2 b ([2b-Pd8 ]4+ ) and the optimized models [Pd8 (meso-Ph2 PCH2 P(H)CH2 P(H)CH2 PH2 )4 (CH3 CN)2 ]4+ ([Pd8 Ph8 ]4+ ) and [Pd8 (meso-H2 PCH2 P(H)CH2 P(H)CH2 PH2 )4 (CH3 CN)2 ]4+ ([Pd8 H8 ]4+ ), with and without empirically calculating dispersion force stabilization energy (B3LYP-D3, B3LYP), the formation energy between the two Pd4 fragments is assumed to involve mainly noncovalent interactions (ca. -70 kcal/mol) with four sets of interligand C-H/π interactions and Pd⋅⋅⋅Pd metallophilic one, while electron shared covalent interactions are almost canceled out within the Pd8 chain. All the compounds isolated are stable in solution and exhibit characteristic absorption at ∼900 nm, which is assignable to a spin allowed HOMO to LUMO transition, and shows temperature dependent intensity change with variable absorption coefficients presumably due to coupling with some thermal vibrations. The structures and electronic states of the Pd8 chains are found finely tunable by varying the terminal capping ligands. In particular, theoretical calculations elucidated that the HOMO-LUMO energy gap is systematically related to the central Pd-Pd distance (2.7319(6)-2.7575(6) A) by two ways with neutral ligands L (1, 2, 3) and with anionic ligands X (4), which are reflected on the NIR absorption energy of 867-954 nm. The isocyanide terminated Pd8 complexes (3) further reacted with excess of RNC (6 eq) to afford the Pd4 complexes, [Pd4 (meso-dpmppm)2 (RNC)2 ](BF4 )2 (13), and the cyclic voltammograms of 2 a (L=CH3 CN), 3, and 13 (R=Xyl, Mes, t Bu, Cy) demonstrated wide range redox behaviors from 2{Pd4 }4+ to 2{Pd4 }0 through 2{Pd4 }2+ ↔{Pd8 }4+ , {Pd8 }3+ , and {Pd8 }2+ strings. The oxidized complexes, [Pd4 (meso-dpmppm)2 (RNC)3 ](BF4 )4 (16), were characterized by X-ray analyses, and the two-electron reduced chain of [Pd8 (meso-dpmppm)4 ](BF4 )2 (7) was analyzed by spectroscopic and electrochemical techniques and DFT calculations. Reactions of 2 a with 1 equiv. of aromatic linear bisisocyanide (BI) in CH2 Cl2 deposited insoluble coordination polymers, {[Pd8 (meso-dpmppm)4 (BI)](BF4 )4 }n (5), and interestingly, they were soluble in acetonitrile, 31 P{1 H} and 1 H DOSY NMR spectra as well as SAXS curves suggesting that the coordination polymers may exist in acetonitrile as dynamically 1D self-assembled coordination polymers comprising ca. 50 units of the Pd8 rod averaged within the timescale.

Binuclear Pd(II) and Pt(II) complexes supported by

The exploration of dynamic molecular crystals is a fascinating theme for materials scientists owing to their fundamental science and potential application to molecular devices. Herein, a one-dimensional (1D) rhodium-dioxolene complex is reported that exhibits drastic changes in properties with the phase transition. X-ray photoelectron spectroscopy (XPS) revealed that the room-temperature (RT) phase is in a mixed-valence state, and therefore, the drastic changes originate from the mixed-valence state appearing in the RT phase. Another notable feature is that the mean square displacements of the rhodium atoms along the 1D chain dramatically increased in the RT phase, indicating a large-amplitude vibration of the Rh-Rh bonds. From these results, a possible mechanism for the appearance of the mixed-valence state in the RT phase was proposed based on the thermal electron transfer from the 1D d-band to the semiquinonato π* orbital coupled with the large-amplitude vibration of the Rh-Rh bonds.

Presented here is a comprehensive study of highly oxidized multiple‐decker complexes composed of TbIII and CdII ions and two to five phthalocyaninato ligands, which are stabilized by electron‐donating n‐butoxy groups. From X‐ray structural analyses, all the complexes become axially compressed upon ligand oxidation, resulting in bowl‐shaped distortions of the ligands. In addition, unusual coexistence of square antiprism and square prism geometries around metal ions was observed in +4e charged species. From paramagnetic 1H NMR studies on the resulting series of triple, quadruple and quintuple‐decker complexes, ligand oxidation leads to a decrease in the magnetic anisotropy, as predicted from theoretical calculations. Unusual paramagnetic shifts were observed in the spectra of the +2e charged quadruple and quintuple‐decker complexes, indicating that those two species are actually unexpected triplet biradicals. Magnetic measurements revealed that the series of complexes show single‐molecule magnet properties, which are controlled by the multi‐step redox induced structural changes., This work was financially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP14J02656 (Y.H.), JP20225003 (M.Y.), JP15K05467 (K.K.), JP24750119 (K.K.), 18K14242 (Y.H.), 19K05401(Y.K), Tohoku University Molecule & Material Synthesis Platform in Nanotechnology Platform Project, CREST, JST JPMJCR12L3 (M.Y.), PhD scholarship from the Beilstein‐Institut zur Förderung der Chemischen Wissenschaften (M.D.), the German‐Japanese University Consortium (HeKKSaGOn), the state of Baden‐Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 40/467‐1 FUGG (JUSTUS cluster), European Union (ERC StG 2012–306826 e‐GAMES), Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER‐BBN), the Spanish Ministry of Economy and Competitiveness (projects FANCY CTQ2016‐80030‐R, MOTHER MAT2016‐80826‐R and the “Severo Ochoa” Programme for Centers of Excellence in R&D, SEV‐2015‐0496), Generalitat de Catalunya (2017SGR918), 111 Project (B18030) from China (M.Y.), the scientific grants R‐143‐000‐A80‐114, R‐143‐000‐A65‐133 from the National University of Singapore. We thank Dr. Norihisa Hoshino for EPR measurements, Dr. Tetsuko Nakaniwa and Prof. Dr. Genji Kurisu and Dr. Takefumi Yoshida for SCXRD measurements. This paper is Contribution No. 62 from the Research Center for Thermal and Entropic Science.