Solid-State Properties of Hexaazatriphenylenehexacarbonitrile HAT(CN) Radical Anions in Crystalline Salts Containing Cryptand(M ) and Crystal Violet Cations.

Crystalline {Cryptand[2.2.2](Na )}{HAT(CN) }⋅0.5C H Cl (1), {Cryptand[2.2.2](K )}{HAT(CN) } (2), (CV ){HAT(CN) } (3), and (CV ){HAT(CN) }⋅2C H Cl (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) are studied. The formation of HAT(CN) in 1-4 leads to the appearance of new bands in the visible range, at 694 and 740 nm. The HAT(CN) radical anions have spin state S=1/2 and are packed in one-dimensional stacks containing the {HAT(CN) } dimers alternated with weaker interacting pairs of HAT(CN) in 1 and nearly isolated {HAT(CN) } dimers in 2. The {HAT(CN) } dimers are diamagnetic in 1 but they effectively mediate one-dimensional antiferromagnetic coupling of spins within the stacks with moderate exchange interaction of J/k = -80 K. The behaviour of salt 2 is described by a singlet-triplet model for the {HAT(CN) } 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) 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) radical anions in 1 and 4 but in solution g-factor shifts to 1.9964. The electronic structure of HAT(CN) is analysed based on X-ray diffraction data for 2, showing a Jahn-Teller distortion of the radical anion that reduces the symmetry from D to C and splits the initially degenerated LUMOs.