Appending Diverse pi-Extended Acceptors with Tetrathiafulvalene/Dithiafulvalene Donors: Multistate Redox Properties, Radical Ion Generation, and Mid-IR-Absorbing Mixed-Valence States

Three classes of donor-acceptor (D-A) pi-extended chromophores (1-12) were synthesized through a phosphite-mediated cross-coupling reaction, in which the anhydride- or imide-based pi-As and number of tetrathiafulvalene (TTF)/dithiafulvalene (DTF) Ds were systematically changed. Large p rings, such as benzoperylene and coronene, were integrated into the TTF/DTF unit, for the first time, to overcome their high insolubility. The anhydride and imide groups in the pi acceptors can significantly alter the frontier orbitals and influence the optoelectronic properties. The D moieties allow the formation of radical cations (D center dot+) and the pi-extended A moieties aid the formation of radical anions (A(center dot-)) by oxidation/reduction under ambient conditions. The molecules revealed UV/Vis/near-IR absorption, fluorescence extending into the near-IR region, and amphoteric electrochemical properties. Chromophores 10 and 12 show solvatochromism in a wide range of solvents. The pi-As with anhydride functionality allow easier electron uptake, relative to the imide groups, whereas the increasing number of D TTF/DTF units make them easy to oxidize. Interestingly, the trans-TTF-fused molecules (1, 6, and 11) exhibited a mixedvalence state in the mid-IR region ((nu) over tilde = 5130-4000 cm(-1)). Moderate electron coupling between the redox centers is inferred to the compounds being of Robin-Day class II. The multistate redox activity along with panchromism and near-/mid-IR optical absorption of these systems can be attractive towards advanced switchable materials.