Experimental and computational studies of charge-transfer and reduction products of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile: HAT-(CN)(6)
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abstract
The compounds HAT-(CN)6C7H 8CH3CN, 1, {[(Cp)2Co][PF 6]}3HAT-(CN)6, 2, {([n-Bu4N][I]) 3HAT-(CN)6]2}3C6H 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 6[HAT-CN6] were prepared by treatment of HAT-CN 6 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. 2004 Springer Science+Business Media, Inc.
