| Institution: | 1. Department of Kinetics and Catalysis, Institute of Problems of, Chemical Physics RAS, 142432 Chernogolovka, Russian Federation;2. Institute of Solid State Physics RAS, 142432 Chernogolovka, Russian Federation;3. Department of Kinetics and Catalysis, Institute of Problems of, Chemical Physics RAS, 142432 Chernogolovka, Russian Federation
Moscow State University, Leninskie Gory, 119991 Moscow, Russia;4. Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502 Japan |
| Abstract: | Crystalline {Cryptand2.2.2](Na+)}{HAT(CN)6.?}?0.5C6H4Cl2 ( 1 ), {Cryptand2.2.2](K+)}{HAT(CN)6.?} ( 2 ), (CV+){HAT(CN)6.?} ( 3 ), and (CV+){HAT(CN)6.?}?2C6H4Cl2 ( 4 ) salts (where CV+ is the crystal violet cation) containing hexaazatriphenylenehexacarbonitrile radical anions have been obtained. The solid-state molecular structure as well as the optical and magnetic properties of HAT(CN)6.? are studied. The formation of HAT(CN)6.? in 1 – 4 leads to the appearance of new bands in the visible range, at 694 and 740 nm. The HAT(CN)6.? radical anions have spin state S=1/2 and are packed in one-dimensional stacks containing the {HAT(CN)6.?}2 dimers alternated with weaker interacting pairs of HAT(CN)6.? in 1 and nearly isolated {HAT(CN)6.?}2 dimers in 2 . The {HAT(CN)6.?}2 dimers are diamagnetic in 1 but they effectively mediate one-dimensional antiferromagnetic coupling of spins within the stacks with moderate exchange interaction of J/kB = ?80 K. The behaviour of salt 2 is described by a singlet–triplet model for the {HAT(CN)6.?}2 dimers with an energy gap of 434(±7) K. Magnetic behaviour of both salts agree well with the data of extended Hückel calculations. Salts 3 and 4 contain isolated stacks of alternated HAT(CN)6.? and CV+ ions, and in this case, nearly paramagnetic behaviour is observed with Weiss temperatures of ?1 and ?7 K, respectively. Narrow Lorentzian EPR signals with g = 2.0033–2.0039 were found for the HAT(CN)6.? radical anions in 1 and 4 but in solution g-factor shifts to 1.9964. The electronic structure of HAT(CN)6.? is analysed based on X-ray diffraction data for 2 , showing a Jahn–Teller distortion of the radical anion that reduces the symmetry from D3h to Cs and splits the initially degenerated LUMOs. |
