Experimental and computational studies of charge-transfer and reduction products of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile:: HAT-(CN)6

The compounds HAT-(CN)(6).C7H8.CH3CN, 1, {[(Cp)(2)Co][PF6]}(3)HAT-(CN)(6), 2, {([n-Bu4N][I])(3)HAT-(CN)(6)](2).3C(6)H(6), 3, were prepared and characterized by X-ray crystallography (HAT-CN6 = hexaazatriphenylene-hexacarbonitrile). The bonding in the neutral form of HAT-CN6, (1), is compared to the co-crystallized examples of (HAT-CN6) with [Cp2Co][PF6] (2) and [n-Bu4N][I] (3). In the case of ( 3), the structure consists of layers of HAT-CN6 molecules and four positions of three partially occupied I- anions, one of which participates in a columnar stacking arrangement with HAT-CN6. The nearly black color of crystals of (3) as compared to the light green color of (1) and the dark green color of (2) indicates that significant charge-transfer is occurring between the I- ion and the HAT-CN6 molecules. In addition to investigating the structures of various HAT-CN6 containing samples, the one- and two-electron reduction products K[HAT-(CN)(6)] and K-2[HAT-CN6] were prepared by treatment of HAT-CN6 with appropriate equivalents of K metal and EPR studies were undertaken. The results support the conclusion that the mono-radical is a typical S = 1/2 species and that the doubly-reduced species is a di-radical with a triplet ground state. Density functional theory calculations were carried out on the neutral, mono-anionic, and di-anionic forms of HAT-CN6 to deduce the ground state geometry and spin state of each molecule. The theoretical results are in accord with the lowest energy ground state of [HAT-CN6](2-) being a triplet state.