The first spectroscopic characterization of the VO2 radical is reported along with new results for V17O and tentative assignments for the VO3 and V+2 radicals. These vanadium radicals were investigated in neon matrices at 4 K by electron spin resonance utilizing conventional high temperature vaporization and pulsed laser ablation generation methods. A detailed ESR study of VO2 showed it to be nonlinear with a 2A1 ground state; the g tensor analysis reveals the presence of an excited electronic state (2B1) approximately 1 eV above the ground state. This excited state prediction and the observed nuclear hyperfine interactions (A tensors) for 51V and 17O were compared with theoretical results obtained from various ab initio computational methods. Ab initio calculations with an extended basis set were performed at various levels of theory including UHF, ROHF, CAS-SCF, and MR-SDCI (multireference single and double configuration interaction). While UHF calculations of the hyperfine interaction were grossly in error, the better levels of theory gave qualitative agreement with experiment and provided an aid to interpretation. VO2 is predicted to be a bent 2A1 state, correlating with the linear 2Δ configuration having the odd electron predominantly in the V 3d orbital. VO3 is predicted to be planar C2v, with the odd electron in a b2 orbital localized in the oxygen in-plane n-type p orbitals.

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