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Spin and electron density redistribution upon binding of non-innocent ligand by iron in enzymatic environment: challenges for quantum chemistry

Brocławik E., Borowski T., Radoń M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2014

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Vol. 18, No 3

255--263

EN

The quality of the description of a chemical bond between the metal (acti ve site) and the ligand (substrate) critically depends on the electronic pro cesses accompanying the bond formation. However, as far as transition metal centers ( TM ) in enzymes are considered, most of the properties 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).

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Zastosowanie teorii funkcjonałów gęstości do modelowania właściwości elektronowych skorpionianowych kompleksów oksodimolibdenowych

Romańczyk P., Brocławik E.

Chemik

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2011

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Vol. 65, nr 10

1093-1100

PL

W artykule, na przykładzie skorpionianowych kompleksów oksodimolibdenowych o mieszanej walencyjności, przedstawiono zastosowanie modelowania DFT do określenia i interpretacji fizycznej wpływu wzajemnej orientacji grup [MoII,INO]3+,2+ (par donorowo- akceptorowych, D-A) na przepływ gęstości 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.

EN

This paper presents the application of DFT modelling in the determination and physical interpretation of the effect of mutual orientation of [MoII, INO] 3+,2+ groups (donor-acceptor pairs, D-A) on the electron density flow in the Mo-O-Mo moiety, exemplified by oxodimolybdenum scorpionate 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.

3

Cu+, Ag+ and Na+ Cationic Sites in ZSM-5 Interacting with Benzene: DFT Modeling

Załucka J., Kozyra P., Mitoraj M., Brocławik E., Datka J.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 9

1801-1808

EN

Synthesis and characterization of new multimodal porous systems containing thin MFI zeolitic films is reported. These films cover the internal surface of the meso- and macroporous silica-alumina monoliths. They are easily accessible through the open porous structure retained in the partially 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.

4

EPR and quantum chemical studies on structural changes in MoO3 upon reduction

Brocławik E., Łabanowska M., Jurkiewicz A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 3

359-371

EN

On the basis of EPR signals registered during reduction of MoO(3) a sequence of structural changes leading to creation of paramagnetic centres has been proposed. Electronic and geometrical structures obtained from quantum chemical calculations for cluster models describing creation of various 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).

5

Quantum chemical verification of new paramagnetic Mo(V) centre in MnO3

Brocławik E., Łabanowska M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 4

303-311

EN

The aim of our work was independent verification of the proposed from EPR experiment uncommon nature of paramagnetic Mo(V) species lacking molybdenyl oxygene For this purpose quantum chemical DFT calculations have been carried out for [MoO(5)H8](3+) cluster model of reduced MOO3. Good 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.