Synthesis and properties of thiophene-functionalized π-extended tetrathiafulvalenes

Toward Redox-Active Indenofluorene-Extended Tetrathiafulvalene Oligomers-Synthesis and Studies of Dimeric Scaffolds

The promotion of mixed-valence interactions between redox-active, π-conjugated scaffolds is of interest when developing new conducting or electrochromic materials as well as in the construction of redox-controlled supramolecular assemblies. In this work, dimeric structures of the redox-active indenofluorene-extended tetrathiafulvalene (IF-TTF) unit were synthesized in a stepwise protocol. The synthesis relied on the development of a new unsymmetrical IF-TTF building block by a combination of phosphite-mediated and Horner-Wadsworth-Emmons reactions for introduction of the dithiafulvene units. The redox properties were studied by cyclic voltammetry, where it was observed that a first one-electron oxidation, corresponding to a mixed-valence state, occurs at a significantly lower potential when the IF-TTF unit is incorporated into a dimer, compared to a monomer analogue. This result indicates that locking the redox-active IF-TTF units in close proximity promotes intramolecular mixed-valence interactions. A computational study was also conducted, supporting the involvement of intramolecular interactions.

Dimethyl 2,5-bis(5-hexylthiophen-2-yl)benzene-1,4-dioate

In the title compound, C₃₀H₃₈O₄S₂, the centroid of the benzene ring lies on a center of inversion. The thio­phene ring is aligned at 49.8 (1)° with respect to the benzene ring. The alkyl chain adopts an extended zigzag conformation.