Experimental and Computational Studies of Charge-Transfer and Reduction Products of 1, 4, 5, 8, 9, 11-Hexaazatriphenylene-Hexacarbonitrile: HAT-(CN)6

• Published in: Journal of cluster science Vol. 15; no. 4; pp. 503 - 530
• Main Authors: Szalay, P. S., Gal n-Mascar s, J. R., Schottel, B. L., Bacsa, J., P rez, L. M., Ichimura, A. S., Chouai, A., Dunbar, K. R.
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01-12-2004
• Subjects: Atomic energy levels; Charge transfer; Color; Crystallization; Crystallography; Density functional theory; Ground state; Molecular structure; Radicals
• ISSN: 1040-7278; 1572-8862
• DOI: 10.1007/s10876-004-5772-6

The compounds HAT-(CN)6 · C7H8 · CH3CN, 1, {[(Cp)2Co][PF6]}3HAT-(CN)6, 2, {([n-Bu4N][I])3HAT-(CN)6]2} · 3C6H6, 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 K6[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.