Electron-molecular vibration coupling in trimerized isostructural mixed-stack complexes (EDT-TTF-I)TCNQF (n = 0, 1, 2).

Infrared and Raman spectra of three isostructural charge transfer complexes (EDT-TTF-I)TCNQF (n = 0, 1, 2) are studied. The planar molecules in these complexes are arranged in one-dimensional stacks formed by donor-acceptor-donor (DAD) centrosymmetric trimeric units with a different degree of charge transfer between D and A. In the IR electronic spectra two bands attributed to D → D and D → A charge transfer transitions are distinguished.

Mixed-ligand, radical, gold bis(dithiolene) complexes: from single-component conductors to controllable NIR-II absorbers.

Neutral radical bis(dithiolene) gold complexes [Au(dt)]˙ are known to exhibit a strong absorption in the 1400-2000 nm NIR absorption range. Here, we demonstrate that the NIR signature of mixed-ligand bis(dithiolene) gold complexes [Au(dt)(dt)]˙ associating two different dithiolene, dt and dt, is found at higher energy, out of the range of the homoleptic analogs [Au(dt)]˙ and [Au(dt)]˙, in the looked-after NIR-II 1000-1400 nm absorption range. An efficient synthetic approach towards precursor mixed-ligand monoanionic gold bis(dithiolene) complexes [Au(dt)(dt)] is reported.

Selective Activation of Chalcogen Bonding: An Efficient Structuring Tool toward Crystal Engineering Strategies.

ConspectusAmong the noncovalent interactions available in the toolbox of crystal engineering, (ChB) has recently entered the growing family of σ-hole interactions, following the strong developments based on the halogen bonding (XB) interaction over the last 30 years. The monovalent character of halogens provides halogen bonding directionality and strength. Combined with the extensive organic chemistry of Br and I derivatives, it has led to many applications of XB, in solution (organo-catalysis, anion recognition and transport), in the solid state (cocrystals, conducting materials, fluorescent materials, topochemical reactions, .

Carborane-based heteromolecular extended networks driven by directional C-Te⋯N chalcogen bonding interactions.

We demonstrate that -(TeMe)carborane directs, in the presence of linear ditopic neutral Lewis bases, the formation of co-crystals with 1D extended supramolecular networks. Specifically, the network formation is systematically stabilized by short and quasi-linear C-Te⋯N chalcogen-bonding (ChB) interactions. In sum, we report efficient carborane-based tectons to rationally design high-dimensional neutral heteromolecular networks.

A Bimetallic Benzene-1,2,4,5-Tetrathiolate (btt) Molybdenocene Complex Cp Mo(btt)MoCp : Radical and Diradical States.

Benzene-1,2,4,5-tetrathiolate (btt) has been used as a bridging ligand to prepare a redox active (molybdenocene dithiolene)-based bimetallic complex Cp Mo(btt)MoCp , which exhibits four successive electron transfers up to the tetracation. Spectro-electrochemical investigations together with DFT and TD-DFT calculations evidence that the two electroactive MoS C metallacycles are electronically coupled in the monocationic as in the dicationic state. Two salts of the dication [Cp Mo(btt)MoCp ] have been structurally characterized with PF and HSO counterions, showing different chair or boat conformations associated with variable folding angles of the two MoS C metallacycles along the S-S hinge.

A highly conducting mixed-valence nickel bis(dithiolene) salt [EtN][Ni(Me-thiazSe-dt)] with selone substitution.

The prototypical [Ni(dmit)] complex (dmit: 1,3-dithiole-2-thione-4,5-dithiolate) is modified here by combining the N-R substitution found in [Ni(R-thiazdt)] complexes (R-thiazdt: -alkyl-thiazoline-2-thione-4,5-dithiolate) and the selone substitution found in [Ni(dmiSe)] complex (dmiSe: 1,3-dithiole-2-selone-4,5-dithiolate) to give a novel -methyl substituted, radical anionic complex formulated as [Ni(Me-thiazSe-dt)] (Me-thiazSe-dt: -methyl-thiazoline-2-selone-4,5-dithiolate). Both this anionic complex and its mixed-valence EtN salt crystallize with a rare arrangement of the two dithiolene ligands around the Ni atom. In the 1 : 2 [EtN][Ni(Me-thiazSe-dt)] salt, the complexes organize into dimerized chains well isolated from each other, giving the salt a strong one-dimensional character.

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

Highly conducting, mixed-valence, multi-component nickel bis() salts were obtained by electrocrystallization of the monoanionic species [Ni(Me-thiazds)] (Me-thiazds: -methyl-1,3-thiazoline-2-thione-4,5-diselenolate), with 1:2 and 1:3 stoichiometries depending of the counter ion used (EtN and BuN PhP, respectively). This behavior strongly differs from that of the corresponding monoanionic 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.

-Chlorobenzimidazoles as efficient and structurally diverse amphoteric halogen bond donors in crystal engineering.

The ability of amphoteric -chlorobenzimidazoles to self-associate into 1D chains through strong and linear N-Cl⋯N halogen bond interactions is demonstrated. The less polarisable Cl atom is strongly activated thanks to the intramolecular amphoteric character and the intermolecular cooperativity effect. The obtained family of compounds featuring different substitution patterns provides opportunities toward the elaboration of macroscopic polar structures.

Topochemical, Single-Crystal-to-Single-Crystal [2+2] Photocycloadditions Driven by Chalcogen-Bonding Interactions.

The face-to-face association of (E)-1,2-di(4-pyridyl)ethylene (bpen) molecules into rectangular motifs stabilized for the first time by chalcogen bonding (ChB) interactions is shown to provide photoreactive systems leading to cyclobutane formation through single-crystal-to-single-crystal [2+2] photodimerizations. The chelating chalcogen bond donors are based on original aromatic, ortho-substituted bis(selenocyanato)benzene derivatives 1-3, prepared from ortho-diboronic acid bis(pinacol) ester precursors and SeO and malononitrile in 75-90 % yield. The very short intramolecular Se⋅⋅⋅Se distance in 1-3 (3.

N-Iodosaccharin-pyridine co-crystal system under pressure: experimental evidence of reversible twinning.

This work presents a single-crystal X-ray diffraction study of an organic co-crystal composed of N-iodosaccharin and pyridine (NISac·py) under hydrostatic pressure ranging from 0.00 (5) GPa to 4.5 (2) GPa.

Topochemical Polymerization of a Diacetylene in a Chalcogen-Bonded (ChB) Assembly.

The successful topochemical polymerization of bis(selenocyanatomethyl)butadyine 1 is achieved upon association in a 1 : 1 co-crystal with 1,2-bis(2-pyridyl)ethylene (2-bpen) through strong and linear (NC)-Se⋅⋅⋅N chalcogen bonding (ChB) interactions, allowing for an appropriate parallel alignment of the diacetylene moieties toward the solid-state reaction. Co-crystal 1⋅(2-bpen) undergoes polymerization upon heating at 100 °C. The reaction progress was monitored by IR, DSC and PXRD.

Chalcogen Bonding in Co-Crystals: Activation through 1,4-Perfluorophenylene vs. 4,4'-Perfluorobiphenylene Cores.

The ability of alkylseleno/alkyltelluroacetylenes such as bis(selenomethylethynyl)-perfluorobenzene () to act as a ditopic chalcogen bond (ChB) donor in co-crystals with ditopic Lewis bases such as 4,4'-bipyridine is extended here to the octafluorobiphenylene analog, 4,4'-bis(selenomethylethynyl)-perfluorobiphenyl (), with the more electron-rich 4,4'-bipyridylethane (), showing in the 1:1 ()•() co-crystal a shorter and more linear C-Se•••N ChB interaction than in ()•(), with Se•••N distances down to 2.958(2) Å at 150 K, i.e.

Introducing Selenium in Single-Component Molecular Conductors Based on Nickel Bis(dithiolene) Complexes.

Two selenated analogues of the all-sulfur single-component molecular conductor [Ni(Et-thiazdt)] (Et-thiazdt = -ethylthiazoline-2-thione-4,5-dithiolate) have been prepared from their precursor radical-anion complexes. Replacement of the thione by a selenone moiety gives the neutral [Ni(Et-thiazdt)] complex. It adopts an unprecedented solid-state organization (for neutral nickel complexes), with the formation of perfectly eclipsed dimers and very short intermolecular Se···Se contacts (81% of the van der Waals contact distance).

Supramolecular rectangles through directional chalcogen bonding.

Supramolecular rectangles are built from the 2+2 chalcogen bonding-based (ChB) association of 1,8-bis(telluromethylethynyl)-anthracene (BTMEA) and ditopic Lewis bases such as 4,4'-bipyridyl-ethane and analogs, demonstrating the strength and directionality of the ChB interaction in such alkynyl-telluroalkyl derivatives.

A radical mixed-ligand gold bis(dithiolene) complex.

A mixed-ligand bis(dithiolene) gold complex is isolated from scrambling reaction of two neutral radical symmetric complexes. Its asymmetric character translates into specific structural and electronic properties including larger electrochemical and optical band gaps than those of both precursors.

Activating Chalcogen Bonding (ChB) in Alkylseleno/Alkyltelluroacetylenes toward Chalcogen Bonding Directionality Control.

Activation of a deep electron-deficient area on chalcogen atoms (Ch=Se, Te) is demonstrated in alkynyl chalcogen derivatives, in the prolongation of the (C≡)C-Ch bond. The solid-state structures of 1,4-bis(methylselenoethynyl)perfluorobenzene (1Se) show the formation of recurrent chalcogen-bonded (ChB) motifs. Association of 1Se and the tellurium analogue 1Te with 4,4'-bipyridine and with the stronger Lewis base 1,4-di(4-pyridyl)piperazine gives 1:1 co-crystals with 1D extended structures linked by short and directional ChB interactions, comparable to those observed with the corresponding halogen bond (XB) donor, 1,4-bis(iodoethynyl)-perfluorobenzene.

Strong σ-Hole Activation on Icosahedral Carborane Derivatives for a Directional Halide Recognition.

Crystal engineering based on σ-hole interactions is an emerging approach for realization of new materials with higher complexity. Neutral inorganic clusters derived from 1,2-dicarba-closo-dodecaborane, substituted with -SeMe, -TeMe, and -I moieties on both skeletal carbon vertices are experimentally demonstrated herein as outstanding chalcogen- and halogen-bond donors. In particular, these new molecules strongly interact with halide anions in the solid-state.

Activating both Halogen and Chalcogen Bonding Interactions in Cation Radical Salts of Iodinated Tetrathiafulavalene Derivatives.

Halogen bonding (XB) interactions are investigated in cation radical salts of bis(methylthio)-5,5'-diiodotetrathiafulvalene (1). Electrocrystallization of 1 in the presence of Bu NCl affords a 1 : 1 salt formulated as (E-1)Cl. Particularly strong I⋅⋅⋅Cl XB interactions are observed around the Cl anion with the distances at 78 % the sum of the van der Waals radii, a consequence of the XB charge activation in the cation radical.

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

Introduction of hydrogen bonding (HB) interactions in single component conductors derived from nickel and gold bis(dithiolene) complexes is explored with the 2-alkylthio-1,3-thiazole-4,5-dithiolate (RS-tzdt) with R = CHCHOH through the preparation of the neutral [Ni(HOEtS-tzdt)] (closed-shell) and [Au(HOEtS-tzdt)]˙ (radical) complexes. At variance with many other radical gold dithiolene complexes which have a strong tendency to dimerize in the solid state, [Au(HOEtS-tzdt)]˙ crystallizes into uniform stacks interconnected by strong O-HN HB involving the nitrogen atom of the thiazole ring. [Au(HOEtS-tzdt)]˙ is isostructural with its neutral, closed-shell nickel analog [Ni(HOEtS-tzdt)], a rare situation in this metal bis(dithiolene) chemistry.

Electronic engineering of a tetrathiafulvalene charge-transfer salt via reduced symmetry induced by combined substituents.

A 1 : 1 metallic charge-transfer salt is obtained by cosublimation of (Z,E)-(SMe)2Me2TTF and TCNQ. X-ray diffraction studies confirm the formation of segregated stacks comprising donor and acceptor molecules in [(E)-(SMe)2Me2TTF](TCNQ). The crystal packing features lateral SS interactions between TTF stacks, which is in sharp contrast to that in (TTF)(TCNQ).

Co-crystals of an organic triselenocyanate with ditopic Lewis bases: recurrent chalcogen bond interactions motifs.

Organic selenocyanates R-Se-CN can act as an amphoteric chalcogen bond (ChB) donor (through the Se atom) and acceptor (through the N atom lone pair). Co-crystallization of tri-substituted 1,3,5-tris(selenocyanatomethyl)-2,4,6-trimethylbenzene (1) is investigated with different ditopic Lewis bases acting as chalcogen bond (ChB) acceptors to investigate the outcome of the competition, as ChB acceptor, between the nitrogen lone pair of the SeCN group and other Lewis bases involving pyridinyl or carbonyl functions. In the presence of tetramethylpyrazine (TMP), benzoquinone (BQ) and para-dinitrobenzene (pDNB) as ditopic Lewis bases, a recurrent oligomeric motif stabilized by six ChB interactions is observed, involving six SeCN groups and the ChB acceptor sites of TMP, BQ and pDNB in the 2:1 adducts (1)·TMP, (1)·BQ and (1)·pDNB.

Charge localization in 1D tetramerized organic conductors: the special case of (tTTF)ClO.

We report a detailed structural and spectroscopic study of the 1D 2:1 cation radical salt (tTTF)ClO, where tTTF  =  trimethylenetetrathiafulvalene, which exhibits a semiconductor-semiconductor phase transition at ca. T  =  137 K. Crystal structures are determined above and below the transition; the tTTF molecules in stacks are grouped into weakly interacting tetramers.

Ambipolar Discotic Liquid Crystals Built Around Platinum Diimine-Dithiolene Cores.

Platinum diimine dithiolene complexes bearing mesogenic groups on one or both ligands have been prepared through an original ligand metathesis reaction to introduce the dithiolene ligand. The neutral diimine ligands, the intermediate platinum dichloride diimine complexes, and the target compounds were characterized by a combination of electronic (electrochemistry, absorption and emission spectroscopy, DFT calculations) and structural (SAXS, DSC) tools. Several novel liquid crystalline platinum diimine-dithiolene were identified over a large temperature range, and the systems were endowed with ambipolar properties, associated with the high reversibility of both oxidation and reduction processes.

Mn-Fe Heterometallic Compounds within Hydrogen-Bonded Supramolecular Networks Promoted by an [Fe(CN)(CNH)] Building Block: Structural and Magnetic Properties.

The reaction of [Fe(CN)] and [Mn(acacen)] (Hacacen = N, N'-bis(acetylacetone)ethylenediamine) building units in the presence of supramolecular cations, [(F-Anil)(18-crown-6)] (F-Anil = 3-fluoroanilinium) or [(Me-F-Anil)(18-crown-6)] (Me-F-Anil = 3-fluoro-4-methylanilinium), affords two new bimetallic compounds, [(F-Anil)(18-crown-6)][Mn(acacen)Fe(CN)(CNH)]·MeOH (1) and [(Me-F-Anil)(18-crown-6)][Mn(acacen)(MeOH)Fe(CN)(CNH)]·MeOH (2), respectively. Compound 1 exhibits a one-dimensional topology, while compound 2 is a dinuclear discrete system due to the coordination of a MeOH molecule at the axial position of the [Mn(acacen)] unit. For both systems, the acidity of the corresponding supramolecular cation triggers the protonation of the Fe moiety as [Fe(CN)(CNH)].

Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (-MeTTF)NO.

A mixed-valence conducting cation radical salt of the unsymmetrically substituted -MeTTF donor molecule (TTF is tetrathiafulvalene) was obtained upon electrocrystallization in the presence of the non-centrosymmetric NO anion. It crystallizes at room temperature in the monoclinic 2/ space group, with the anion disordered on an inversion centre. The donor molecules are stacked along the axis.