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Research has been conducted on the Cu complexes of the bis{(2-pyridyl)ethyl]-appended monoaza crown ether. The results of the X-ray absorption spectroscopic analysis of the complexes are presented.

Copper dioxygen complexes derived from molecular receptor ligands are discussed relative to structure, synthesis and reactivity. The objective of realizing substrate-selective oxidation using a given complex, (2(Cu(II)(sub.2)O(sub.2))) was not realized. The complex was reactive toward phenols, but undesired radical coupling reactions were seen for the most part.

Dinuclear copper complexes containing tridentate dinucleating ligands are prepared and considered as structural and functional models for catechol oxidases. In these complexes, the Cu(II) centers undergo antiferromagnetic coupling. The crystal structure of the complexes remain unchanged in the methanolic solution. The copper complex of 1,5-bis(2-benzimidazolyl)-3-pentanol exhibits catecholase activity by oxidizing 3,5-di-tert-butylcatechol to quinone.

The solvation and structure of aquocobalamin (vitamin B12a, I+) in crystal and aqueous solutions are determined. The EXAFS spectra of the aquocobalamin, perchlorate, 1+ClO(super -)(sub 4), crystals exhibits that, both in solid state and in solution, the coordination of cobalt is same. The single crystal structure analysis shows that 1+ClO(super -)(sub 4) crystallizes in the orthorhombic space group P212121, with approximately 100 solvent water molecules for each unit cell and four 1+ClO4 moieties. In aquocobalamin chloride, an intramolecular hydrogen bonds to the Co(III) axially coordinated water molecule, as given by the nuclear magnetic resonance data.

X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, has been carried out at the Zn K edge of the N-terminal part of the integrase protein of the human immunodeficiency virus, type 2 (HIV-2), and of some zinc coordination compounds. In the presence of excess β-mercaptoethanol, which was present in the NMR structure elucidation of the protein [Eijkelenboom et al. (997), Curr. Biol. 7, 739-746; (2000), J. Biomol. NMR, 18, 119-28], the protein spectrum was nearly identical to that recorded in its absence. Comparison of the XANES of the protein with that of model compounds and literature data permits the conclusion that the Zn ion is four-coordinated. The major shell of the EXAFS provides evidence for a mixed (N or O as well as S) coordination sphere, while the minor shells indicate imidazole coordination. Our approach to the analysis of the EXAFS, including quantification of the imidazole by multiple scattering simulations with EXCURV92, was validated on the model compounds. An important result is that with multiple scattering simulations using restraints on the parameters of the imidazole rings the number of imidazoles and their orientation could be determined. The integrase spectra can be fitted with two sulfur ligands at 2.26 Å (Debye-Wallertype factor 0.009 Ų) and two imidazole ligands with the N atoms at 1.99 Å (Debye-Waller-type factor 0.005 Ų). The XAS-derived geometry is fully consistent with that found in the NMR structure determination and, allowing for the volume contraction due to the temperature difference between the experiments, justifies the restraints applied in the structure calculation (Zn-S and Zn-N distances of 2.3 Å and 2.0 Å, respectively). [ABSTRACT FROM AUTHOR]