DTT-DDQ Mixed-Stack\nOrganic Charge-Transfer Crystals\nwith Near-Infrared Absorption

Dithieno[3,2-<i>b</i>:2′,3′-<i>d</i>]thiophene (DTT) is a common molecular motif in organic\nelectronics.\nWe find that it forms a 1:1 charge-transfer complex (CTC) with the\nelectron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).\nThe 1:1 complex has an alternating donor/acceptor mixed-stack structure,\nand an intense near-infrared absorption band. Vibrational spectroscopy\nand electronic structure calculations are used to further understand\nthe partial ionization induced by the DTT/DDQ complex.