Intermolecular Hydrogen-Bond Networks and Physical Properties of BF₄^– and TCNQ^{<b>•</b>–} Salts of Three-Fold Symmetric Tris(alkylamino)phenalenyliums

Abstract

Synthesis, redox properties, and crystal structures of tris­(alkylamino)­phenalenyliums (TAP) having alkyl groups (<i>n</i>-Pr, <i>i</i>-Pr, <i>t</i>-Bu) and their charge-transfer salts with tetracyanoquinodimethane radical anion (TCNQ^{<b>•</b>–}) were investigated. The electrochemical measurements revealed that TAP exhibits two irreversible reduction processes to neutral radical and anion species. The introduction of an alkylamino group caused a large negative shift of the first reduction potential and a significant decrease of the on-site Coulomb repulsion because of the electron-donating nature of amino groups and the extension of the π-electronic system. In the crystal structures of the BF₄^– salts, the TAP skeleton possesses a nearly 3-fold symmetric molecular plane indicating the delocalization of positive charge. The face-to-face stack of TAP formed π-dimer or columnar structures, which were connected through intermolecular N–H···F hydrogen bonds with BF₄^– to construct multidimensional network structures. The TCNQ^{<b>•</b>–} salts prepared by the metathesis method were characterized as fully ionic salts with a 1:1 component ratio. In the crystal structures, both TAP and TCNQ^{<b>•</b>–} molecules formed π-dimers, and the intermolecular hydrogen bonds between TAP and TCNQ^{<b>•</b>–} constructed a two-dimensional sheet