Structure and magnetic properties of oxoverdazyl radicals and biradicals by an integrated computational approach

The structure, conformational behavior and magnetic properties of 1, 5-dimethyl-3-phenyl-6-oxoverdazyl radical and 1,1',5,5'-tetramethy1-6, 6'-dioxo-3, 3'-biverdazyl biradical and of some related model compounds have been investigated by an integrated computational tool including an hybrid HF/DFT electronic method coupled to the polarizable continuum model for the description of solvent effects. The computed structural parameters are in agreement with the crystal structure for the radical and with refined post-HF computations for a simpler model compound. For the di-radical system a non planar structure is predicted both in vacuo and in solution. The nearly planar conformation found in the solid state can be ascribed to packing effect, as for the well-known biphenyl molecule. The computed exchange coupling constant of the and 1, 1', 5, 5' - tetramethyl-6, 6'-dioxo-3, 3'-biverdazyl di-radical is in remarkable agreement with the experimental value when averaging effects of the inter-ring torsional motion are included in the calculations.