Phenalenyl-Based Highly Conductive Molecular Systems with Hydrogen-Bonded Networks: Synthesis, Physical Properties, and Crystal Structures of 1,3- and 1,6-Diazaphenalenes, and Their Protonated Salts and Charge-Transfer Complexes with TCNQ

Abstract

Abstract Protonated salts and charge-transfer complexes of the 1,3- and 1,6-diazaphenalene (DAP) systems 5–7 have been investigated for new conducting molecule-based materials. Cyclic voltammetry measurements revealed that DAP derivatives are stronger electron donors than hydroquinone, and some of them possess comparable electron-donating abilities to TTF. X-ray crystal structure analyses of HX (X = Br− and BF4−) salts of 5b, 5c, and 6e confirmed their one-dimensional structures by N–H···X···H–N hydrogen bonds and their ability to form hydrogen-bonded networks in charge-transfer complexes. Actually, in the TCNQ salts of protonated 5c·H+ and 7b·H+, N–H···N≡C hydrogen-bonding interactions between DAP molecules and TCNQ molecules constructed a characteristic hydrogen-bonded cyclic tetramer and linear D–A–D triad, respectively. On the other hand, TCNQ complexes of 1,3- and 1,6-DAP derivatives, prepared by a conventional mixing method of each neutral component, were found to be partial charge-transfer complexes with segregated stacking columns as elucidated from IR and electronic spectra. Their compressed pellets exhibited high electrical conductivity (10−2–10−1 S cm−1) at room temperature with semiconducting behavior (activation energy, Ea = 40–80 meV).