Aryl-fused tetrathianaphthalene (TTN): synthesis, structures, properties, and cocrystals with fullerenes

Abstract

1,4,5,8-Tetrathianaphthalene (TTN) is the structural isomer of tetrathiafulvalene (TTF). Herein, the title aryl-fused TTNs (TTN1–TTN9) have been synthesized from a zinc–thiolate complex (TBA)₂[Zn(DMIT)₂] via a two-fold Cu-catalyzed C–S coupling reaction. These TTNs can be transformed into the corresponding aryl-fused TTF isomers by reaction with FeCl₃. The electronic properties of these TTNs were studied by absorption spectroscopy, electrochemistry, and theoretical calculations, which reveal that these TTNs show weak electron donating ability as compared with their TTF isomers. Crystallographic analyses indicate that these TTNs take the chair-like conformation, i.e., having two curved surfaces that are of shape complementary to fullerene molecules. Consequently, these TTNs show strong affinity toward C₆₀/C₇₀ to form cocrystals. In the cocrystals, the fullerene molecules are encapsulated by the curved surfaces of TTN molecules through multiple intermolecular atomic contacts. While the interaction modes between TTNs and fullerene molecules are very similar, the packing patterns of the cocrystals can be finely tuned by varying the solvents. Moreover, the fullerene molecules form tight stacks as column arrays or two-dimensional sheets.