Intermolecular Hydrogen-Bond Networks and Physical Properties of BF4– and TCNQ•– Salts of Three-Fold Symmetric Tris(alkylamino)phenalenyliums

Synthesis, redox properties, and crystal structures of tris­(alkylamino)­phenalenyliums (TAP) having alkyl groups (n-Pr, i-Pr, t-Bu) and their charge-transfer salts with tetracyanoquinodimethane radical anion (TCNQ•–) 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•– 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•– molecules formed π-dimers, and the intermolecular hydrogen bonds between TAP and TCNQ•– constructed a two-dimensional sheet.