The application of the stochastic genetic algorithm (GA) in conjunction with the deterministic Powell search to analysis of the multicomponent powder EPR spectra based on computer simulation is described. This approach allows for automated extraction of the magnetic parameters and relative abundances of the component signals, from the nonlinear least-squares fitting of experimental spectra, with minimum outside intervention. The efficiency and robustness of GA alone and its hybrid variant with the Powell method was demonstrated using complex simulated and real EPR data sets. The unique capacity of the genetic algorithm for locating global minima, subsequently refined by the Powell method, allowed for successful fitting of the spectra. The influence of the population size, mutation, and crossover rates on the performance of GA was also investigated.

DFT calculations of the molecular structure of the intrazeolite η 1 {CuNO} 11 adduct and the 14 N and 17 O hyperfine and 63 Cu superhyperfine coupling constants were performed and compared with previous EPR results. The calculations confirmed the choice of signs adopted in the previous analysis of the experimental data and the character of the SOMO. The influence of the basis set and the exchange-correlation functional on the HFCC and the spin-density distribution was investigated and briefly discussed. The global repartition of the spin density over Cu (F ) 0.11), N(F ) 0.58), and O (F ) 0.34) atoms determined from the Mulliken population analysis compared well with the experiment. The 14 N hyperfine tensor was successfully reproduced with the LanL2DZ basis and BPW91 functional, whereas in the case of the 63 Cu superhyperfine dipolar tensor T the agreement, except for that of the T zz component, was less satisfactory because of an overestimated polarization of the 3d yz orbital, regardless of the computation level. For the calculation of a iso (Cu), because LanL2DZ treats inner electrons with the effective core potential, a 6-311G(df) basis set appeared to be the most appropriate, leading to excellent agreement between the experimental and calculated values.

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Formation of reactive oxygen species (ROS) is of vital importance in catalytic oxidation chemistry. In this paper we have shown that a nonredox system such as amorphous zirconium dioxide (a-ZrO2) is highly active in ROS formation via H2O2 decomposition. Interaction between a-ZrO2 and H2O2 in aqueous solution was investigated by means of EPR, HYSCORE, Raman, and UV–vis, along with auxiliary FTIR, TG-MS, and XPS techniques, in a broad range of pH values and H2O2 concentrations. Various reaction intermediates such as superoxide (O2 •–) and hydroxyl (•OH) radicals as well as peroxide (O2 2–) species were identified. At pH <5.3 the superoxide and hydroxyl radicals were generated simultaneously in large amounts with the peak concentration being reached around the isoelectric point of the gel catalyst. In this pH region, the ZrO2 gel exhibited peroxidase-type activity, quantified by an o-phenylenediamine assay. At pH >5.3 formation of O2 2– is accompanied by a substantial release of O2 due to the pronounced catalase-like activity of a-ZrO2. The role of electroprotic processes (an interfacial proton transfer coupled with an intermolecular electron transfer) in H2O2 decomposition and ROS formation was elucidated, and a plausible mechanism of this reaction, Zr+–HO2 – (surf) + H2O2(aq) → •OH(aq) + Zr+–O2 •– (surf) + H2O, was proposed. The surface of a-ZrO2 covered with hydroxyl groups plays a role of an ionic sponge, which controls the electroprotic equilibrium by capturing the charged reaction intermediates. Unlike the amorphous gel, crystalline zirconia exhibits only weak activity in the production of the O2 •– and •OH radicals, and a different mechanism is involved. It is worth mentioning that the activity of the zirconia gel catalyst in ROS generation, as gauged by the Michaelis–Menten constant, is comparable (ca. 40%) to that of the Fenton-type oxides (Fe3O4, Co3O4).