ABSTRACT:The hydrogen bonding complexes formed between the H 2 O and OH radical have been completely investigated for the first time in this study using density functional theory (DFT). A larger basis set 6-311ϩϩG(2d,2p) has been employed in conjunction with a hybrid density functional method, namely, UB3LYP/6-311ϩϩG(2d,2p). The two degenerate components of the OH radical 2 ⌸ ground electronic state give rise to independent states upon interaction with the water molecule, with hydrogen bonding occurring between the oxygen atom of H 2 O and the hydrogen atom of the OH radical. Another hydrogen bond occurs between one of the H atoms of H 2 O and the O atom of the OH radical. The extensive calculation reveals that there is still more hydrogen bonding form found first in this investigation, in which two or three hydrogen bonds occur at the same time. The optimized geometry parameter and interaction energy for various isomers at the present level of theory was estimated. The infrared (IR) spectrum frequencies, IR intensities, and vibrational frequency shifts are reported. The estimates of the H 2 O ⅐ OH complex's vibrational modes and predicted IR spectra for these structures are also made. It should be noted that a total of 10 stationary points have been confirmed to be genuine minima and transition states on the potential energy hypersurface of the H 2 O ⅐ HO system. Among them, four genuine minima were located.
On the basis of the basic feature of the electron transfer reactions, a new theoretical scheme and application of a nonempirical ab initio method in computing the inner-sphere Ž . reorganization energies RE of hydrated ions in electron transfer processes in solution Ž . are presented at valence STO basis VSTO level. The potential energy surfaces and the various molecular structural parameters for transition metal complexes are obtained Ž . using nonempirical molecular orbital MO calculations, and the results agree very well with experimentally observed ones from vibrational spectroscopic data. The results of inner-sphere REs obtained from these calculations via this new scheme give a good agreement with photoemission experimental findings and those from the improved 2q Ž . . and Co redox couple systems and are better than those from semiempirical INDOrII MO method and other classical methods. Further, the observed agreement of the optimized structural data and the results of inner-sphere REs of complexes with Ž . experimental findings confirms the following: 1 the validity of nonempirical MO calculation method to get accurate structural parameters and inner-sphere RE for the Ž . redox systems for which reliable vibrational spectroscopic data are not available, 2 the Ž . validity of the improved self-exchange model proposed early for inner-sphere RE, and 3
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