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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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Coordination properties of the diethyl (pyridin-3-ylmethyl)phosphonate ligand (3-pmpe) with nitrate transition metal salts

Żurowska B., Kotyński A., Ochocki J.

Materials Science Poland

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2009

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Vol. 27, No. 4/1

999--1007

EN

A new series of nitrate transition metal complexes containing diethyl(pyridin-3-ylmethyl)phosphonate (3-pmpe) as a ligand, having a general formula [M(3-pmpe)2(H2O)2](NO3)2 (M = Cu, Co and Ni) and [Zn(3-pmpe)2](NO3)2 were prepared. The complexes were identified and characterized by the elemental analysis, spectroscopic and magnetic studies. Ligands containing two donor atoms, heterocyclic nitrogen and phosphoryl oxygen atoms bind in a bidentate bridging manner via the pyridine nitrogen and the phosphoryl oxygen atoms. The magnetic behaviour in the temperature range 1.8-300 K) of the Cu(II), Ni(II), Co(II) complexes as well as their spectroscopic properties suggest polymeric structure of all complexes and the existence of a weak antiferromagnetic exchange coupling between paramagnetic centres inside the dibridged linear chains [M(3-pmpe)2M]n.

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Coordination properties of the diethyl 2-quinolilmethylphosphonate ligand with chloride and nitrate transition-metal salts

Żurowska B., Mroziński J., Ochocki J.

Materials Science Poland

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2007

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Vol. 25, No. 4

1063--1074

EN

A new series of the chloride and nitrate transition metal complexes containing the ligand diethyl 2-quinolylmethylphosphonate (2-qmpe) of general formula M(2-qmpe)(NO3)2 (M = Cu, Co), [Zn(2-qmpe)(H2O)2NO3]NO3ź H2O, [Ni(2-qmpe)(H2O)2NO3]NO3, M(2-qmpe)2Cl2 (M = Cu, Ni, Co, Pd) and M(2-qmpe)Cl2 (M = Co, Zn) were prepared. The complexes were identified and characterized by elemental analysis, spectroscopic and magnetic studies. Ligand containing two donor atoms, heterocyclic nitrogen and phosphoryl oxygen atoms exhibits different coordination properties. It was shown that the ligand binds in a bidentate chelate manner via the quinoline nitrogen and the phosphoryl oxygen atoms (complexes with 1:1 metal to ligand molar ratio) and it can also acts as a monodentate ligand coordinated through the nitrogen in the Pd(II) or oxygen atom in the Cu(II) and Co(II) complexes (complexes with 1:2 metal to ligand molar ratio). The magnetic behaviour of the Cu(II), Ni(II) and Co(II) and spectroscopic investigation of Zn(II) complexes suggests mononuclear structure of all the complexes and the existence of a weak intermolecular exchange coupling between magnetic centres inside crystal lattice.