Synthesis and structures of 11,11,12,12-tetracyano-2,6-diiodo-9,10-anthraquinodimethane and its 2:1 cocrystals with anthracene, pyrene and tetrathiafulvalene

Radical salts and charge-transfer complexes (CTCs) containing tetracyanoquinodimethane (TCNQ) display electrical conductivity, which has led to the development of many TCNQ derivatives with enhanced electron-accepting properties that are applicable toward organic electronics. To expand the family of TCNQ derivatives, we report the synthesis and structures of 11,11,12,12-tetracyano-2,6-diiodo-9,10-anthraquinodimethane (abbreviated as DITCAQ), C20H6I2N4, and its charge-transfer complexes with various electron donors, namely DITCAQ-anthracene (2/1), C20H6I2N4·0.5C14H10, (I), DITCAQ-pyrene (2/1), C20H6I2N4·0.5C16H10, (II), and DITCAQ-tetrathiafulvalene (2/1), C20H6I2N4·0.5C6H4S4, (III). The molecular structure of DITCAQ consists of a 2,6-diiodo-9,10-dihydroanthracene moiety with two malononitrile substituents. DITCAQ possesses a saddle shape, since the malononitrile groups bend significantly up out of the plane of the central ring and the two benzene rings bend down out of the same plane. π-π interactions between DITCAQ and the electron-donor molecules control the degree of charge transfer in cocrystals (I), (II), and (III), which is reflected in both the dihedral angles between the terminal benzene ring and the central ring on the DITCAQ motifs, and their corresponding IR spectra.