Breathing Some New Life into an Old Topic: Chalcogen-Nitrogen π-Heterocycles as Electron Acceptors †

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First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives : design, synthesis, crystal structures, electronic and electrical properties

The authors are grateful to the Royal Society (RS International Joint Project 2010/R3), Deutsche Forschungsgemeinschaft (project 436 RUS 113/967/0-1 R), the Russian Foundation for Basic Research (project 10-03-00735), the Presidium of the Russian Academy of Sciences (projects 7.17, 8.14 and P-8), and to the Siberian Branch of the Russian Academy of Sciences (project 105) for funding.The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.PostprintPeer reviewe

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives:design, synthesis, crystal structures, electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.</p

Coordination of Halide and Chalcogenolate Anions to Heavier 1,2,5-Chalcogenadiazoles: Experiment and Theory

New products of coordination of anions X^– (X = F, I, PhS) to the Te atom of 3,4-dicyano-1,2,5-telluradiazole (<b>1</b>) were synthesized in high yields and characterized by X-ray diffraction (XRD) as the salts [(Me₂N)₃S]⁺[<b>1</b>-F]⁻ (<b>9</b>), [K­(18-crown-6)]⁺[<b>1</b>-I]⁻ (<b>10</b>), and [K­(18-crown-6)]⁺[<b>1</b>-SPh]⁻<b>·</b>THF (<b>11</b>), respectively. In the crystal lattice of <b>10</b>, I atoms are bridging between two Te atoms. The bonding situation in anions of the salts <b>9</b>–<b>11</b> and some other adducts of 1,2,5-chalcogenadiazoles (chalcogen = S, Se, Te) and anions X^– (X = F, Cl, Br, I, PhS) was studied using DFT, QTAIM, and NBO calculations, for <b>9</b>–<b>11</b> in combination with UV–vis, IR/Raman, and MS-ESI techniques. In all cases, the nature of the coordinate bond is negative hyperconjugation involving the transfer of electron density from X^– to the heterocycles. The energy of the bonding interaction varies in a range from ∼30 kcal mol^–1 comparable with energies of weak chemical bonds (e.g., internal N–N bond in organic azides) to ∼86 kcal mol^<b>–</b>1 comparable with an energy of the C–C covalent bonds. The thermodynamics of the anions’ coordination to <b>1</b> and their Se and S congeners was also studied by quantum chemical calculations. The general character of this reaction and favorable thermodynamics in the case of heavier chalcogens (Se, Te) were established. Comparison with available data on acyclic analogues, i.e. the chalcogen diimines RNXNR, reveals that they also coordinate various anions but in addition reactions across XN (X = S, Se, Te) double bonds. Attempts to prepare the anion [<b>1</b>-TePh]⁻ led to disintegration of <b>1</b>. The only unambiguously identified product was a rather rare tellurocyanate that was characterized by XRD and elemental analysis as the salt [K­(18-crown-6)]⁺[TeCN]⁻ (<b>13</b>)

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives:design, synthesis, crystal structures, electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.</p