The coordination chemistry of 1,3-dithiole-2-thione-4,5-dithiolate (dmit) and isologs

Mixed-Valence Conductors from Ni Bis(diselenolene) Complexes with a Thiazoline Backbone

Highly conducting, mixed-valence, multi-component nickel bis(diselenolene) salts were obtained by electrocrystallization of the monoanionic species [Ni(Me-thiazds)₂]^-1 (Me-thiazds: N-methyl-1,3-thiazoline-2-thione-4,5-diselenolate), with 1:2 and 1:3 stoichiometries depending of the counter ion used (Et₄N⁺ and nBu₄N⁺ vs Ph₄P⁺, respectively). This behavior strongly differs from that of the corresponding monoanionic dithiolene complexes whose oxidation afforded the single component neutral species. This provides additional rare examples of mixed-valence conducting salts of nickel diselenolene complexes, only known in two examples with the dsit (1,3-dithiole-2-thione-4,5-diselenolate) and dsise (1,3-dithiole-2-selone-4,5-diselenolate) ligands. The mixed-valence salts form highly dimerized or trimerized bi- and trimetallic units, rarely seen with such nickel complexes. Transport measurements under a high pressure (up to 10 GPa) and band structure calculations confirm the semiconducting character of [Ph₄P][Ni(Me-thiazds)₂]₃ and the quasi metallic character of [Et₄N][Ni(Me-thiazds)₂]₂ and [NBu₄]_x[Ni(Me-thiazds)₂]₂ salts (0 < x < 1).

A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion

Dichalcogenolenes are archetypal redox non-innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2-protected imidazolium salt. This ligand is diamagnetic, which is in contrast to the paramagnetic nature of standard dichalcogenolene monoanions. The new ligand is also redox-active, as demonstrated by isolation of a stable diselenolene radical dianion. The unique electronic properties of the new ligand give rise to unusual coordination chemistry. Thus, preparation of a hexacoordinate aluminum tris(diselenolene) complex and a Lewis acidic aluminate complex with two ligand-centered unpaired electrons was achieved.

A Semiconductive Nature of Bis(dithiolato)nickelate Radical Salt Exhibiting Broadband Photoconduction

The fractional oxidation state [M(dmit)₂] (dmit^2- = 2-thioxo-1, 3-dithiole-4, 5-dithiolate) salts have long attracted attention in the molecular metal area owing to high conductivity and even superconductivity. In this study, we achieved a mixed-valence salt (1) of [Ni(dmit)₂]^0.5- with monovalent 1,3-N,N-dimethyl-imidazolium (DiMIm⁺) by a solvent evaporation approach under ambient conditions. The mixed valence of [Ni(dmit)₂]^0.5- has been characterized by an analysis of the IR spectrum and crystal structure. In the crystal structure of 1, two [Ni(dmit)₂]^0.5- anions overlap in an eclipsed mode to form a [Ni(dmit)₂]₂^1- dimer, featuring a radical bearing an S = 1/2 spin; the dimeric radicals stack into a column along the b axis, and the adjacent columns connect together via the lateral-to-lateral S···S contacts along the a axis, and through the head-to-head S···S contacts along the [101] direction. Salt 1 shows the magnetic behavior of an S = 1/2 Heisenberg antiferromagnetic uniform linear chain with J/k_B = -47.5(4) K and a semiconducting feature with σ = 2.52 × 10^-3 S cm^-1 at 293 K, 2.32 × 10^-2 S cm^-1 at 373 K, and E_a = 0.22 eV, as well as broadband photoconductivity under irradiation of green and white lights. This study suggests the possibility of designing new photoconductors based on the mixed-valence [Ni(dmit)₂]^0.5- salt.

Modern History of Organic Conductors: An Overview

This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have been cited with full titles and arranged in chronological order. Among the research conducted over ~70 years, topics from the last two decades are discussed in more detail than the rest. Unlike other papers in this issue, this review will help readers to understand the origin of each topic within the field of organic conductors and how they have evolved. Due to the advancements achieved over these 70 years, the field is nearing new horizons. As history is often a reflection of the future, this review is expected to show the future directions of this research field.

Magnetism, dielectrics and ion conduction in two polymorphs of a heteroleptic bis(dithiolato)nickelate molecular solid

A new heteroleptic compound [triethylpropylammonium][Ni(dmit)(mnt)] with two crystal polymorphs, which show different magnetic and dielectric properties, has been reported.

Hydrogen bonding interactions in single component molecular conductors based on metal (Ni, Au) bis(dithiolene) complexes

Nickel (closed-shell) or gold (radical) bis(dithiolene) neutral complexes, functionalized with hydroxyethyl and thiazole moieties, afford hydrogen-bonded single component conductors.

Sulfur-rich Graphdiyne-Containing Electrochemical Active Tetrathiafulvalene for Highly Efficient Lithium Storage Application

A sulfur-rich graphdiyne (TTF-GDY) material containing electrochemically active unit of tetrathiafulvalene was successfully synthesized at the liquid/liquid interface under mild conditions. The extended two-dimensional (2D) π-conjugated framework contains large in-plane cavities to accommodate defined sulfur elements and precise sulfur content. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterizations demonstrated that the TTF-GDY adopted the layered structures. X-ray photoelectron spectroscopy (XPS), Raman spectrum, selected area electron diffraction (SAED), crystal modeling, and molecular-mechanics-based calculation further confirmed the proposed framework structure and the expected chemical compositions. Considering the unique structure and sulfur-rich characteristic, we then applied this material as an electrode in lithium battery applications. Due to the unique 2D framework structure, the TTF-GDY exhibited a high specific capacity of 837.6 mAh/g, particularly having a robust long-term stability under the high current density. These results demonstrated that such a sulfur-rich TTF-GDY, as a novel electrochemical material would have great application potential in energy fields.

A Novel Derivative of Hexathiocane having the 4,5-Dimethylthio-1,3-Dithiol-2-Ylidene Moiety

An unexpected reaction forming 4,8-bis(4,5-dimethylthio-1,3-dithiol-2-ylidene)-1,2,3,5,6,7-hexathiocane is described.

Single-Component Conductors: A Sturdy Electronic Structure Generated by Bulky Substituents

While the introduction of large, bulky substituents such as tert-butyl, -SiMe3, or -Si(isopropyl)3 has been used recently to control the solid state structures and charge mobility of organic semiconductors, this crystal engineering strategy is usually avoided in molecular metals where a maximized overlap is sought. In order to investigate such steric effects in single component conductors, the ethyl group of the known [Au(Et-thiazdt)2] radical complex has been replaced by an isopropyl one to give a novel single component molecular conductor denoted [Au(iPr-thiazdt)2] (iPr-thiazdt: N-isopropyl-1,3-thiazoline-2-thione-4,5-dithiolate). It exhibits a very original stacked structure of crisscross molecules interacting laterally to give a truly three-dimensional network. This system is weakly conducting at ambient pressure (5 S·cm(-1)), and both transport and optical measurements evidence a slowly decreasing energy gap under applied pressure with a regime change around 1.5 GPa. In contrast with other conducting systems amenable to a metallic state under physical or chemical pressure, the Mott insulating state is stable here up to 4 GPa, a consequence of its peculiar electronic structure.

CS2activation at uranium(iii) siloxide ate complexes: the effect of a Lewis acidic site

Multimetallic cooperativity plays an important role in U(iii) mediated CS₂reduction: the reductive dimerization of CS₂occurs preferentially at a heterodimetallic U, K complex while the reductive disproportionation pathway is favoured by the “ate” complex [K(18c6)][U(OSi(O^tBu)₃)₄].

Hydrogen-bonding interactions in a single-component molecular conductor: a hydroxyethyl-substituted radical gold dithiolene complex

The anionic hydroxyethyl-substituted gold dithiolene complex [NEt4][Au(EtOH-thiazdt)2] is synthesized and further oxidized to the neutral radical species [Au(EtOH-thiazdt)2](•) through electrocrystallization. Single-crystal X-ray diffraction studies highlight the existence of the two cis and trans isomers for the monoanionic complex, with involvement of the hydroxy group in intermolecular O-H···S hydrogen-bonding interactions. The neutral radical complex, [Au(EtOH-thiazdt)2](•), is isostructural with its known ethyl analogue, namely, [Au(Et-thiazdt)2](•). It exhibits a semiconducting behavior (σRT = 0.05-0.07 S cm(-1)) at room temperature and ambient pressure with an activation energy of 0.14 eV. Comparison of the crystal structures and transport and magnetic properties with those of the prototypical [Au(Et-thiazdt)2](•) single-component conductor shows that the replacement of ethyl by a slightly bulkier hydroxyethyl substituent affects only weakly the overlap interactions, complemented here by added O-H···S hydrogen-bonding interactions.

Radical or not radical: compared structures of metal (M = Ni, Au) bis-dithiolene complexes with a thiazole backbone

A complete series of dianionic, monoanionic, and neutral dithiolene complexes formulated as [Ni(Et-thiazdt)2](n), with n = -2, -1, 0, and Et-thiazdt: N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate, is prepared using an optimized procedure described earlier for the N-Me derivatives. Electrochemical and spectroscopic properties confirm the electron-rich character of the Et-thiazdt dithiolate ligand. The three complexes are structurally characterized by single-crystal X-ray diffraction. The paramagnetic anionic complex [Ni(Et-thiazdt)2](-1), as Ph4P(+) salt, exhibits side-by-side lateral interactions leading to a Heisenberg spin chain behavior. The solid-state structure of the neutral, diamagnetic [Ni(Et-thiazdt)2](0) complex shows a face-to-face organization with a large longitudinal shift, at variance with the structure of its radical and neutral gold dithiolene analogue described earlier and formulated as [Au(Et-thiazdt)2](•). Comparison of the two structures, and those of the other few structurally characterized pairs of Ni/Au dithiolene complexes, demonstrates the important role played by overlap interactions between gold dithiolene radical species. Despite its closed-shell character, the neutral nickel complex [Ni(Et-thiazdt)2](0) exhibits a semiconducting behavior with a room-temperature conductivity σRT ≈ 0.014 S cm(-1).

Crystal structures, CO₂ adsorption, and dielectric properties of [Cu(II)₂(R-benzoate)₄(pyrazine)]∞ polymers (R = m-F, 2,3-F₂, m-Cl, and m-CH₃)

m-Fluorobenzoate (m-FBA), 2,3-difluorobenzoate (2,3-F2BA), m-methylbenzoate (m-MBA), and m-chlorobenzoate (m-ClBA) were introduced into the Cu(II) binuclear unit as bridging ligands between two Cu(II) sites, which were further connected by an axial pyrazine (pz) ligand to form one-dimensional coordination polymers of [Cu(II)2(m-FBA)4(pz)]∞ (1), [Cu(II)2(2,3-F2BA)4(pz)]∞ (2), [Cu(II)2(m-MBA)4(pz)]∞ (3), and [Cu(II)2(m-ClBA)4(pz)]∞ (4), respectively. The parallel arrangements of one-dimensional (1D) polymers result in 1D channels between the polymers that crystallization CH3CN molecules can occupy to form single crystals of 1·4CH3CN, 2·4CH3CN, 3·2CH3CN, and 4·2CH3CN. Both π-dimer and dipole-dipole interactions were simultaneously observed in the interchain interactions of m-FBA and/or 2,3-F2BA ligands in crystals 1 and 2. The sizes of the one-dimensional channels between the polymers are thus modulated according to the interchain interactions between the polar BA ligands. CH3CN molecules within the channels were easily replaced by H2O under ambient conditions. CO2 adsorption-desorption isotherms of crystals 1, 2, and 3 at 195 K indicated gate-adsorption with a hysteresis, whereas two-step gate-adsorption behavior was observed for CO2 in crystal 4. Temperature- and frequency-dependent dielectric responses were not observed in crystals 1-4 under vacuum conditions, whereas dielectric anomalies were observed around 290 K for crystals 1 and 2 with adsorbed CO2. CO2 desorption from the channels in crystals 1 and 2 activated the molecular motions of polar BA ligands and dielectric responses around 290 K, which were confirmed from CO2 adsorption-desorption isotherms around 290 K and differential scanning calorimetries under CO2 conditions.

Experimental and theoretical investigation of the magnetic and photoconductive nature of a novel two-dimensional, mixed-valence bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickelate molecular solid

A novel, two-dimensional mixed-valence [Ni(dmit)₂] molecular solid shows a rapid, clear and stable response of photoconductivity under UV irradiation.

Second order non-linear optical activity of arsenic and antimony dithiolene complexes

Synthesis and characterization of dithiolene complexes of arsenic and antimony in trivalent state have been reported. A four coordinated structural motif results in a ladder like arrangement in the arsenic complex due to the inter-anionic As-S interaction which is replaced by Sb-π interaction with the counter cation in the solid state structure of the similar antimony complex. Electronic structure calculations on ground state geometries and the time-dependent density functional theoretical calculations were performed in order to characterize the absorption spectra incorporating solvent effects. Notably, both the complexes display intense second order optical non-linearity as has been determined using hyper-Rayleigh scattering technique in dichloromethane solution and the results are corroborated by DFT calculations.

Crystal structures and magnetic properties of (4,4'-phenylazophenyl)diammonium(crown ethers)[Ni(dmit)2]2 crystals

Sandwich-type hydrogen-bonded supramolecular dications (DAAz(2+))([18]crown-6)(2) and (DAAz(2+))(dicyclohexane[18]crown-6)(2) (DAAz(2+) = 4,4'-(phenylazophenyl)diammonium) were introduced into [Ni(dmit)(2)](-) anions via a diffusion method to form novel single crystals (DAAz(2+))([18]crown-6)(2)[Ni(dmit)(2)](2) (1) and (DAAz(2+))(dicyclohexane[18]crown-6)(2)[Ni(dmit)(2)](2) (2), respectively, which were characterized based on their crystal structures and magnetic susceptibilities. The molecular assembly structures and its physical properties were expanded in the use of a three component molecular network system. The two ammonium groups (-NH(3)(+)) of the DAAz(2+) dication formed N-H(+)-O hydrogen-bonding interactions with the oxygen atoms of [18]crown-6 and dicyclohexane[18]crown-6. In the case of crystal 1, an alternating π-stacking interaction was observed for the [Ni(dmit)(2)](-) anions, whereas orthogonal linear π-S interactions were detected for crystal 2. Temperature-dependent magnetic susceptibilities of crystals 1 and 2 followed the alternate Heisenberg antiferromagnetic chain (J = -15.8 K) and linear Heisenberg antiferromagnetic chain (J = -13.7 K) models, respectively.

Sulfur-based redox reactions in Mo3S7(4+) and Mo3S4(4+) clusters bearing halide and 1,2-dithiolene ligands: a mass spectrometric and density functional theory study

The gas phase fragmentation reactions of sulfur-rich [Mo(3)S(7)Br(6)](2-) (1(2-)), [Mo(3)S(7)(bdt)(3)](2-) (2(2-)), and [Mo(3)S(4)(bdt)(3)](2-) (3(2-)) (bdt = benzenedithiolate) complexes have been investigated by electrospray ionization (ESI) tandem mass spectrometry and theoretical calculations at the density functional theory level. Upon collision induced dissociation (CID) conditions, the brominated 1(2-) dianion dissociates through two sequential steps that involves a heterolytic Mo-Br cleavage to give [Mo(3)S(7)Br(5)](-) plus Br(-) followed by a two-electron redox process that affords [Mo(3)S(5)Br(5)](-) and diatomic S(2) sulfur. Dianion [Mo(3)S(7)(bdt)(3)](2-) (2(2-)) dissociates through two sequential redox processes evolving diatomic S(2) sulfur and neutral bdt to yield [Mo(3)S(5)(bdt)(3)](2-) and [Mo(3)S(5)(bdt)(2)](2-), respectively. Conversely, dianion [Mo(3)S(4)(bdt)(3)](2-) (3(2-)), with sulfide instead of disulfide S(2)(2-) bridged ligands, remains intact under identical fragmentation conditions, thus highlighting the importance of disulfide ligands (S(2)(2-)) as electron reservoirs to trigger redox reactions. Regioselective incorporation of (34)S and Se at the equatorial position of the Mo(3)S(7) cluster core in 1(2-) and 2(2-) have been used to identify the product ions along the fragmentation pathways. Reaction mechanisms for the gas-phase dissociation pathways have been elucidated by means of B3LYP calculations, and a comparison with the solution reactivity of Mo(3)S(7) and Mo(3)S(4) clusters as well as closely related Mo/S/dithiolene systems is also discussed.