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

Three binary charge-transfer (CT) compounds resulting from the donor 2,2 ' : 6 ',2 '' : 6 '',6-trioxotriphenylamine (TOTA) and the acceptors F(4)TCNQ and F(4)BQ and of a pyrene-annulated azaacene (PAA) with the acceptor F(4)TCNQ 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 center dot F(4)TCNQ, a 2 : 1 donor : acceptor ratio in (TOTA)(2)center dot F(4)BQ, and a rare 4 : 1 stoichiometry in (PAA)(4)center dot F(4)TCNQ, respectively. Metrical parameters of the donor (D) and acceptor (A) constituents as well as IR spectra indicate full CT in TOTA center dot F(4)TCNQ, partial CT in (TOTA)(2)center dot F(4)BQ and only a very modest one in (PAA)(4)center dot F(4)TCNQ. Intricate packing motifs are present in the crystal lattice with encaged, pi-stacked (F(4)TCNQ(-))(2) dimers in TOTA center dot F(4)TCNQ or mixed D/A stacks in the other two compounds. Their solid-state UV-vis-NIR spectra feature CT transitions. The CT compounds with F(4)TCNQ are electrical insulators, while (TOTA)(2)center dot F(4)BQ is weakly conducting.

Automated summary

Three binary charge-transfer (CT) compounds formed by the donor 2,2':6',2'':6'',6-trioxotriphenylamine (TOTA) and the acceptors F(4)TCNQ and F(4)BQ, as well as a CT compound formed by a pyrene-annulated azaacene (PAA) and the acceptor F(4)TCNQ, were reported. The identities of these compounds were confirmed by various spectroscopic techniques and single-crystal X-ray diffraction. The crystal structures revealed different stoichiometries for each compound, and the spectroscopic data indicated varying degrees of charge transfer. The compounds exhibited intricate packing motifs in the crystal lattice and showed CT transitions in the solid-state UV-vis-NIR spectra. The electrical conductivity of the compounds varied, with the CT compounds containing F(4)TCNQ being insulators and (TOTA)(2)·F(4)BQ showing weak conductivity.