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

The structure, conformational behavior and magnetic properties of 1, 5-dime thyl-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 inv estigated by an integrated computational tool including an hybrid HF/DFT el ectronic method coupled to the polarizable continuum model for the descript ion of solvent effects. The computed structural parameters are in agreement with the crystal structure for the radical and with refined post-HF comput ations 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 co nformation found in the solid state can be ascribed to packing effect, as f or the well-known biphenyl molecule. The computed exchange coupling constan t of the and 1, 1', 5, 5' - tetramethyl-6, 6'-dioxo-3, 3'-biverdazyl di-rad ical is in remarkable agreement with the experimental value when averaging effects of the inter-ring torsional motion are included in the calculations .