related to their electronic structure are extre mely challenging for quantum chemistry. Especially severe problems appear for the bonding of NO to fe rrous sites, e.g. in myoglobin or non-heme enzymes. Therefore, special care has to be shown in t he assessment of a quantum chemical method employed with respect to its power in des cribing the properties of interest. In this work we discuss spin-resolved Fe-NO charge transfe rs and their relation to the metal spin state, with special attention paid to the interpretation of t he bonding between NO and the transition metal center in terms of dative or covalent contributi ons; furthermore, the impact of spin and the electron transfer on the reactivity of the center is discussed. The stress is put on the role of the coordinating environment in controlling the re action mechanism via fine-tuning of the spin and the oxidation status of the metal core. This goe s in line with the high significance of spin in enzymatic reaction mechanisms ( cf. multi-state reactivity proposed for iron enzymes).

elektronowej we fragmencie Mo-O-Mo. Zależność struktury elektronowej, tj. lokalizacji/ delokalizacji niesparowanego elektronu od wzajemnego położenia lokalnych układów współrzędnych D i A, może nadawać kompleksom właściwości molekularnych przełączników i reostatów.

complexes of mixed valence. The relationship between the electron structure, i.e. localization/ delocalization of unpaired electron and mutual position of D and A coordinate systems, may bestow the properties of molecular switches and rheostats on complexes.

recrystallized, originally amorphous monolith. When the mesoporous Al-SBA-15 sieves are used in stead of monoliths, a controlled hydrothermal process results in the formation of the MFI nanodomains dispersed in the walls that separate mesopores hexagonally arranged. These do mains possess strong acidic sites of the zeolitic type, but the original ordering of mesopores in the parent material is very well retained. A simple method for the synthesis of the MFI crystals containing both meso- and macrovoids is also proposed. It makes use of the suspended mono- and polydispersed carbon particles that serve as porogens. Thus, the porous MFI crystals obtained can be used for the preparation of effective bifunctional catalysts by the de position of a highly dispersed metallic (Pd) phase.

oxygen vacancies were compared with EPR interpretation of the studied paramagnetic species. Thanks to good agreement between experimental and theoretical results it was possible to verify the nature of paramagnetic sites in reduced MoO(3).

agreement between the energy level diagram elucidated from EPR data with calculated orbital energies led to the conclusion that the structure of this Mo(V) centre seems to be well founded.