Strong Iodine... Oxygen Interactions in Molecular Conductors Incorporating Sulfonate Anions
Résumé
Strong I***O halogen bonds are identified in a series of cation radical salts of the donor molecule 3,4-diiodo-3′,4′-ethylenedithiotetrathiafulvalene (EDT-TTFI2, 1) with ClO4- and various organic sulfonates, such as racemic camphor sulfonate, 1,5- and 2,6-naphtalene bis(sulfonate), and 2,6-anthracene bis(sulfonate). In all compounds, oxygen atoms of sulfonate moieties appear thus as powerful halogen bonding acceptors with I***O distance much shorter than the van der Waals contacts (down to 77%). A full charge transfer (ρ = 1) is found in (1)ClO4 and (1)2[2,6-Napth(SO3)2], with a dimerization of the stacks of 1*+ cation radicals and a diamagnetic behavior. The mixed-valence (ρ = 1/2) salts (1)2[(rac)-camph(SO3)]*Solv, (1)5[2,6-Anthr(SO3)2], and (1)4[1,5-Napht(SO3)2] form conducting stacks with semiconducting behavior. Band structure calculations and magnetic measurements performed on (1)4[1,5-Napht(SO3)2] show a strongly one-dimensional electronic structure, at the origin of the semiconducting behavior.