Structural and optical investigations of charge transfer complexes involving the F4TCNQ dianion?

CrystEngComm Pub Date: 2014-05-08 DOI: 10.1039/C4CE00289J

Abstract

7,7,8,8-Tetracyano-2,3,4,5-tetrafluoroquinodimethane (F4TCNQ) in its dianionic form, F4TCNQ2?, is shown to form charge transfer complexes with a wide variety of organic cations. The structures and spectroscopic properties of fourteen F4TCNQ2? salts are described, thirteen of which have colours consistent with the formation of charge transfer complexes. Unlike neutral F4TCNQ charge transfer complexes, the dianion, F4TCNQ2? is able to act as a donor in its interaction with suitable cations that serve as acceptors in solid-state complexes. The F4TCNQ2? salts described in this work have been categorised into five different structural types according to the relative arrangements of cations and anions. In each case, structural and IR spectroscopic data indicate that the anions retain a formal ?2 charge upon formation of the salt. The optical band gaps, determined from Vis-NIR spectra, are found to have the lowest values when the cation is a viologen, either methyl viologen or diphenylmethyl viologen.

Graphical abstract: Structural and optical investigations of charge transfer complexes involving the F4TCNQ dianion
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