Shape-shifting in contorted dibenzotetrathienocoronenes

Abstract

We detail a general method for the synthesis of dibenzotetrathienocoronenes and elucidate their solid state structures in crystals and co-crystals. The contorted dibenzotetrathienocoronene (c-DBTTC) is a tetrathiophene-fused version of the previously studied contorted hexabenzocoronenes (c-HBC). The synthesis detailed here is simple and provides easy access to this important class of materials. We have found that these materials display molecular flexibility and tunable supramolecular self-assembly properties in the solid state by shifting molecular conformations between two different conformations. Depending on the conditions under which a c-DBTTC-containing material crystallizes, the c-DBTTC adopts either the “up-down” or the “butterfly” conformation. When grown from the vapor phase, crystals of the unsubstituted c-DBTTC show the molecule only in the up-down conformation, and it packs into dense crystals containing columnar arrays with close intracolumnar packing. The packing is controlled by the inherent molecular corrugation of the three-dimensional core and sulfur–sulfur interactions. When grown as co-crystals with electron acceptors from solution, the butyl-substituted c-DBTTC either adopts the butterfly conformation when the electron acceptor is small enough to be completely enveloped (TCNQ) or the up-down conformation when the electron acceptor is relatively large (C₆₀). When grown from organic solvent crystals of the butyl-substituted c-DBTTC contain molecules of the solvent as the only guest, and we observe both conformations of the c-DBTTC. Controlling the supramolecular structure is the key to developing these materials for electronic applications.