Hartree-Fock linear response calculations of g-tensors of substituted benzene radicals

Linear response theory has been applied for calculations of g-tensors of or ganic radicals in order to test the range of validity of restricted Hartree -Fock reference states. The g-values were calculated for the benzene cation (C6H6+), the benzene anion (C6H6-), hydropyrazine (C4H5N2), the dihydropyr azine cation (C4H6N2+), the aniline radical (C6H5NH), the p-benzoquinone an ion (C6H4O2-), phenoxyl (C6H5O), the nitrobenzene anion (C6H5NO2-), and the nitropyridine anion (C5H4N2O2-). Influence of variations of structural par ameters on the g-tensor components were investigated. Calculated g-values w ere in excellent agreement with experiment for six out of nine radicals. Tw o radicals - the p-benzoquinone anion and aniline radical - showed minor di screpancies, while the g-tensor of the phenoxyl radical was incorrect. The problem with the phenoxyl radical was traced to a complex electronic struct ure and optical spectrum. Results consistent with experiment could in that case only be obtained with electron correlated calculations. (C) 1999 Elsev ier Science B.V. All rights reserved.