O complexo Cu II -N-benzoilglicina provê um sistema conveniente para se estudar interações de troca fracas entre elétrons desemparelhados que são transmitidas por caminhos químicos de interesse biológico. A molécula existe como um dímero onde cada Cu II está coordenado a cinco ligantes, formando uma pirâmide de base quadrada distorcida. O único caminho químico entre íons Cu II magneticamente não-equivalentes envolve 17 átomos diamagnéticos e uma fraca ligação de hidrogênio putativa. Esta interação foi estudada por Ressonância Paramagnética Eletrônica de amostras monocristalinas a 9,5 e 34,5 GHz, tendo sua magnitude sido calculada em 4(1) mK. Esse valor é discutido em termos de valores obtidos para caminhos similares em outros compostosmodelo e proteínas.The complex Cu II -N-benzoylglycine provides a convenient system to study weak exchange interactions between unpaired spins transmitted through a biologically relevant long chemical bridge.The molecule exists as a dimer with each Cu II ion coordinated to five ligands, forming a distorted square-based pyramid. The only chemical connection between magnetically non-equivalent copper ions is a very long path comprising 17 diamagnetic atoms and a weak putative hydrogen bond. This interaction was studied using Electron Paramagnetic Resonance in single-crystal samples at 9.5 and 34.5 GHz and its magnitude was calculated as 4(1) mK. This value is discussed in terms of values obtained for similar paths in other model compounds and in proteins.Keywords: electron paramagnetic resonance, exchange interactions, model systems
IntroductionToluene and other volatile organic compounds (VOCs) 1 are widely used as organic solvents in pharmacological, plastic and rubber industries, as well as in various materials such as paints, adhesives and combustion materials.2 The exposure to high concentration of toluene and other VOCs causes adverse health effects in nervous system, 3 mucous and dermal irritations, 4 and chromosome aberrations. 5,6 Toluene is metabolized in human liver microsomes 7,8 or in rat hepatic microsomes 9,10 by the hepatic cytochrome P450-mediated mixed function oxidase system to benzyl alcohol, to benzoic acid and finally to hippuric acid, by conjugation with glycine to yield hippuric acid or N-benzoylglycine, which is then excreted in urine.
11Copper is a bioessential element with relevant oxidation states. 12,13 Due to the complexity of metalobiomolecules and the associated problems, a very useful way of gaining information is examining the behavior of simpler model compounds. The study of ion complexes of copper-amino acids 14-26 (or peptides) 27-31 and copper-nucleoside (or related bases) 32,33 has been a topic of increasing interest in the last few years, manly due to their relevance in the development of new reagents for biotechnology and medicine. 34 N-benzoylglycine is structurally similar to a dipeptide except for the absence of the N-terminal group. Due to its high affinity for Cu II , the dimeric complex Cu II -N-benzoylglycine could form in vivo, especia...