Organic binary charge-transfer compounds of 2,2' : 6',2'' : 6'',6-trioxotriphenylamine and a pyrene-annulated azaacene as donors.

Abstract

Three binary charge-transfer (CT) compounds resulting from the donor 2,2' : 6',2'' : 6'',6-trioxotriphenylamine (TOTA) and the acceptors F4TCNQ and F4BQ and of a pyrene-annulated azaacene (PAA) with the acceptor F4TCNQ are reported. The identity of these CT compounds are confirmed by single-crystal X-ray diffraction as well as by IR, UV-vis-NIR and EPR spectroscopy. X-ray diffraction analysis reveals a 1 : 1 stoichiometry for TOTA·F4TCNQ, a 2 : 1 donor : acceptor ratio in (TOTA)2·F4BQ, and a rare 4 : 1 stoichiometry in (PAA)4·F4TCNQ, respectively. Metrical parameters of the donor (D) and acceptor (A) constituents as well as IR spectra indicate full CT in TOTA·F4TCNQ, partial CT in (TOTA)2·F4BQ and only a very modest one in (PAA)4·F4TCNQ. Intricate packing motifs are present in the crystal lattice with encaged, π-stacked (F4TCNQ-)2 dimers in TOTA·F4TCNQ or mixed D/A stacks in the other two compounds. Their solid-state UV-vis-NIR spectra feature CT transitions. The CT compounds with F4TCNQ are electrical insulators, while (TOTA)2·F4BQ is weakly conducting.