The hybrid DFT and molecular orbital study of structure and molecular bonding of FeO4 and FeO4-
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The structures, vibrational frequencies and molecular bonding of FeO4 and FeO4- species with different spin states have been investigated by the hybrid DFT, ab initio Hartree-Fock and post-Hartree-Fock molecular orbital methodologies. For FeO4- the properties of the ground state strongly depend on the level of the calculation. The quasi-tetrahedron FeO4- (B-2(1)) was predicted to be the lowest by DFT and MP4(SDQ) calculations, while the doubler (O-2)FeO4- ((2)A(2)) was found to be the lowest at CISD/B3P86 and CCSD/B3P86 levels. The ground state of neutral FeO4 species is the singlet (O-2)FeO2 ((1)A(1)) at B3P86 and CISD/B3P86 levels of theory. Most of the strong bands for the isomers of FeO4 and FeO4- appear at about 1000 cm(-1). The molecular bondings in FeO4 and FeO4- species containing cyclic Fe(O-2) subunits, bring about a net charge transfer from Fe and the bonding pi orbital into anti-bonding pi orbital of O-2 which activate the O-O bond in coordinated O-2. Larger O-O bond lengths in the cyclic Fe(O-2) subunits than in the isolated O-2 and O-2 were observed. (C) 1999 Elsevier Science B.V. All rights reserved.