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Within this work we have investigated spiro‐based tetrathiafulvalenes (TTFs) obtained as mixtures of stereoisomers from racemic spiro[5.5]undeca‐1,8‐dien‐3‐one. Compared to previously described spiro‐TTFs, enantiomeric and diastereoisomeric forms have been here separated by chiral HPLC and fully characterized both experimentally and theoretically. The two types of spiro‐based chiral derivatives contain either one (2) or three (1) chiral centres out of each one is spiro‐type. Experimental CD, supported by TD‐DFT calculations, shows differences in the optical activity between the 1 and 2 and their intermediates. The low optical activity of 2 and 3 (spiro alone chirality) was attributed to the presence of two conformers in the solution (ax and eq) of opposite Cotton effect whereas in the case of 1 and 5 (spiro and stereogenic centres) the spiro chirality seems to be responsible of the Cotton effect in the high energy region whereas the R and S chirality in the low energy region. Racemic and enantiopure forms have been successfully used for the synthesis of charge transfer complexes with tetracyanoquinodimethane (TCNQ) based acceptors. [ABSTRACT FROM AUTHOR]

Harnessing a bis(selenomethyl)tetrathiafulvalene (TTF) derivative as a donor, conducting charge transfer (CT) salts are realized thanks to original packing structures supported by chalcogen bonding (ChB) interactions. Specifically, reaction of EDT-TTF(SeMe)2 (EDT = ethylenedithio) with an acceptor, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2TCNQ), afforded two polymorphs of 1 : 1 CT salts, α- and β-[EDT-TTF(SeMe)2](F2TCNQ). The donor and the acceptor molecules in both polymorphs organize into segregated and uniform stacks. Based on the structure, the α-salt shows a quasi-complete CT while the β-salt shows a partial CT with ρ ∼±0.8. The oxidation of TTF activates the σ-hole on Se atoms to be engaged in highly linear ChB interactions with the N atoms on F2TCNQ. The formation of directional ChB interactions resulted in original packing structures of the donor and the acceptor stacks that are distinct between α- and β-salts. In particular, the ChB motif observed in the β-salt allows F2TCNQ molecules within the stack to be closer than those in the α-salt. Consequently, the α-salt is a semi-conductor, while the β-salt shows metallic behaviour with a two-step metal-to-insulator (MI) transition. Moreover, the observed MI transition temperature in the β-salt (180 K) is substantially higher than that in other known CT salts, likely owing to the 3D coupling of the modulation in different chains brought about by the –SeMe substituents. [ABSTRACT FROM AUTHOR]

The electrocrystallization of diiodo- and dibromo-ethylenedithiotetrathiafuvalene (EDT-TTFI[sub2] and EDT-TTFBr[sub2]) in the presence of the polymeric 1D [Et[sub4]N][Cd(SCN)[sub3]] as an electrolyte affords two different salts, formulated as [EDT-TTF-I[sub2]][sub4][Cd[sub3](NCS)[sub8]] • CH3CN H[sub2]O (1) and [EDT-TTF-Br[sub2]][sub10][Cd[sub5](SCN)[sub14]] • 2TCE (2), characterized by a two- dimensional segregation of the partially oxidized donor molecules and the polymeric anionic network incorporating embedded solvent molecules. Both salts exhibit a partial charge transfer, that is, p = 0.5 in 1 and an unconventional p = 0.4 in 2. They behave as semiconductors with σ[subRT] = 0.67 and 33 S cm[sup-1] and activation energies of 330 and 370 K for 1 and 2, respectively. Compared with a 1:3 Cd/SCN ratio of the starting electrolyte, the reconstructed, thiocyanate (SCN)-deficient motifs [Cd[sub3](NCS)[sub8]][sub2] and [Cd[sub5](SCN)[sub14]][sub4] organize into layered hollow structures with cavities filled by solvent molecules, halogen-bonded to the halogenated TTF molecules, through a C[subTTF]—N≡C—CH[sub3] interaction in 1, through a type II C[subTTF]—Br⋯CI-CTCE halogen/halogen interaction in 2. Band structure and Fermi surface calculations for the two salts indicate a two-dimensional character, while the semiconducting properties of the salts are attributed to an efficient nesting of the hidden 1D Fermi surfaces. [ABSTRACT FROM AUTHOR]

[EDO-TTF-CONH2][TCNQF4], triclinic system, space group P-1, a=8.2479(12) A˚, b=12.282(2) A˚, c=12.6842(18) A˚, α=113.850(17)°, β=106.420(17)°, γ=90.284(19)°, V=1116.8(4) A˚3; and [EDT-TTF-CONH2]2[TCNQF4], triclinic system, space group P-1, a=6.5858(9) A˚, b=11.699(2) A˚, c=12.2281(18) A˚, α=104.000(19)°, β=93.611(17)°, γ=98.279(19)°, V=899.9(3) A˚3, whose π-donor molecules, (ethylenedioxo)-carbamoyltetrathiafulvalene and (ethylenedithio)-carbamoyltetrathiafulvalene, respectively, differ solely by the nature of the chalcogen atoms in their outer ethylene dichalcogeno bridge, yet form very different charge-transfer complexes with the same π-acceptor. [EDO-TTF-CONH2•+]2 [TCNQF4•−]2 is a diamagnetic insulating ionic salt with a three-dimensional rock-salt-type structure based on discrete dimers while in the semi-conducting mixed-valence complex, [EDT-TTF-CONH2]2•+[TCNQF4•−], the mixed-valence dimers aggregate into infinite chains interspersed within parallel rows of non-interacting radical anions. It is shown how the robust and adaptable supramolecular amide hydrogen bond tweezers-like motifs common to the two solids simply comply to the 3-to-1 dimensionality reduction upon substitution of O for S. [Copyright &y& Elsevier]