Organic selenocyanates can act as powerful chalcogen bond donors, with themselves or with Lewis bases.

Co-crystallisation of the Et₄N⁺ or n-Bu₄N⁺ salts of the thiocyanate anion with o-, m- and p-diodoperfluorobenzene or the sym-trifluorotriiodobenzene allowed for the isolation of six different salts which were structurally characterized by single crystal X-ray diffraction. Halogen bonding interactions are observed between the neutral iodinated molecules acting as halogen bond donors and the S or N ends of the thiocyanate anion, with a variety of bonding modes (terminal as well as bridging), and characterised by short I⋯(N,S) contacts and linear C–I⋯(N,S) motifs. On the other hand, the I⋯N≡C angles present deviations from linearity (145–170°) while the I⋯S–C angles are close to 90°, revealing a type II halogen bond interaction with the S atom acting as pseudo halogen. The observation of structures where only the S or the N atom are engaged in halogen bonding suggests that the two coordination modes are close in energy, as confirmed by DFT calculations and ELF analysis which give also a rationale for the observed structural preferences. This bidentate nature of the SCN ⁻ anion in halogen bonding interactions is reminiscent of its various coordination modes with the Cd²⁺ cation, best understood in terms of the hard–soft acid–base concept.

Racemic and enantiopure ethylenedithio-tetrathiafulvalene-thiomethyl-oxazoline (EDT-TTF-(SMe)-OX) derivatives have been synthesized. Single-crystal X-ray diffraction analyses reveal the establishment of O⋯S nonbonded interactions, unprecedented in the TTF series, characterized by short S⋯O distances and linear O⋯SMe motifs. Theoretical calculations at the DFT/B3LYP level on a model molecule demonstrate that both possible planar s-trans (O⋯S interaction) and s-cis (N⋯S interaction) conformations are energy minima, separated by an extremely weak energy gap. The energy barrier corresponding to the equilibrium between the two forms has been also estimated from DFT calculations, as well as their relative stability in the radical cation state of the TTF. According to the latter, there is a slight tendency towards the enhancement of the N⋯S interactions. Following the predictions of the theoretical calculations, the coexistence of both O⋯S and N⋯S nonbonded interactions is observed in two mixed valence radical cation salts of the racemic TTF with the dianionic cluster Mo₆Cl₁₄, prepared upon electrocrystallization. Interestingly, the ratio TTF : dianion is finely tuned by the choice of the electrocrystallization solvent. Physical measurements such as electrical conductivity and thermoelectric power on single crystals combined with magnetic susceptibility data in one case and extended Hückel tight-binding calculations demonstrate and rationalize the semiconducting behavior of both mixed valence salts. This study demonstrates that intramolecular N⋯S and O⋯S interactions can efficiently modulate and direct in the TTF series the occurrence of original solid-state structures provided with physical properties.

The sulfiding of benzils with P₄S₁₀ in 1,3-dimethyl-2-imidazolidinone (DMI) as solvent allows for a direct synthesis of neutral radical, gold dithiolene complexes based on 1,2-bis-(4-alkoxy-phenyl)ethylene-1,2-dithiolate ligands with n-butyl, n-octyl and n-dodecyl chains. The three neutral and soluble complexes Au-OC₄, Au-OC₈ and Au-OC₁₂ exhibit a near infrared (NIR) absorption band around 1.5 μm and EPR characteristics which confirm a strong delocalization of the spin density on the electron-rich dithiolene ligands. X-Ray crystal structures of Au-OC₄ and Au-OC₁₂ are compared with those of the corresponding nickel complexes. They are characterised by segregation of the alkyl chains into layered structures with a stacking of the radical complexes into alternated spin chains, confirmed by the temperature dependence of the magnetic susceptibility which attests for antiferromagnetic interactions and a singlet ground state. Observations under polarising microscope and DSC experiments do not reveal a thermotropic behaviour for Au-OC₁₂.