Photodecomposition of MnO₄^-: A Theoretical Study

Abstract

The electronic and geometrical structures of the ground states and low-lying isomers of MnO 4 and MnO 4 -have been calculated as a function of spin-multiplicities by using the molecular orbital theory based on generalized gradient approximation to the density functional formalism. Total energies of isomers are used for evaluating the energetics of the MnO 4 -decay through various fragmentation channels. Two primary channels were found depending on the energy of photons. The preferred photofragmentation channel, accessible with ≈2 eV photons, is found to involve an initial excitation of the ground-state MnO 4 -anion into its peroxo isomer followed by subsequent excitations into a superoxo form. Photodetachment of an extra electron from this superoxo isomer anion leads to the formation of a neutral superoxo isomer of MnO 4 , which, in turn, dissociates to MnO 2 + O 2 . Excitations of the anion peroxo isomer into biperoxo isomer are also possible with 3.7 eV, photons and the latter could dissociate spontaneously to MnO 2 -+ O 2 . A number of other decay channels are accessible with low-energy photons, but their intensities are expected to be low because these require flipping the spin of one or more electrons.

Experimental and theoretical study of the photoelectron spectra of MnOx−(x=1–3) clusters

“…This could be due to the fact that all transition metal oxides appear to have a large number of isomers. For example, MnO 4 has at least 10 isomers in the energy range of 2.8 eV, 27 whereas MnO 3 has 8 isomers within 3.5 eV energy range, and MnO 2 has 11 isomers within 4.3 eV energy range, as discovered in the current work.…”

“…These choices are known to yield results in very good agreement with a variety of experiments. 27,[62][63][64] Geometry optimizations were carried out by the steepest descent method until the gradient forces fell below the threshold value of 3ϫ10 Ϫ4 . Subsequent analytical harmonic frequency calculations were performed in order to confirm that the optimized geometries correspond to stationary states.…”

“…[14][15][16][17][18][19][20] Photodecomposition of MnO 4 Ϫ in solutions has also been the subject of several experimental [21][22][23][24][25] and theoretical studies. 26,27 MnO 4 was found to possess very high electron affinity of ϳ5 eV, 28,29 which puts it in the class of superhalogens, 30 since the largest electron affinity of 3.62 eV among all the atoms is that of halogen Cl. 31 Very few ex-perimental studies of MnO 4…”

Electronic structure of chromium oxides, CrOn− and CrOn (n=1–5) from photoelectron spectroscopy and density functional theory calculations

“…A similar approach is applied here to the CrO n Ϫ series, especially for nϭ3 -5, for which there is little previous work. Among the 3d TM oxide anions, theoretical studies have been performed for ScO 2 Ϫ , [20][21][22] TiO n Ϫ , 23 VO n Ϫ , 24 MnO n Ϫ , 14,25,26 and FeO n Ϫ , 27,28 and good agreement between experimental data and the calculated EA's of the corresponding neutral species has generally been obtained. Detailed studies of the electronic and geometrical structure of the neutral and anionic 3d TM monoxides 29 and dioxides 30 have been performed using DFT methods with different generalized gradient approximations for the exchange-correlation functional.…”

O-atom transport catalysis by neutral manganese oxide clusters in the gas phase: Reactions with CO, C2H4, NO2, and O2

“…The hybrid B3LYP exchangecorrelation functional [41][42][43] and a 6-311+G * basis set [44][45][46] are used. This choice of the B3LYP/6-311+G * method with moderate computational cost has been tested to provide reasonable results in previous studies on manganese oxide clusters: 47,48 this approach yields good results in the interpretation of vibrational spectra of manganese oxides. 49 and reactants are calculated at different typical association geometries to obtain the lowest energy structures.…”