title: Ultraviolet spectrophotometric characterization of copper(II) complexes with imidazole N-methyl derivatives of L-histidine in aqueous solution.
abstract: In this study we considered pi-methyl-L-histidine (pi-methis) and tau-methyl-L-histidine (tau-methis) as ligands for copper(II) ion, in order to clarify, by means of ultraviolet (UV) spectroscopy in aqueous solution (T = 25 degrees C, I = 0.1 M), some aspects of the co-ordination mode with respect to other ligands of a previous study in which copper(II) complexes of L-histidine, N-acetyl-L-histidine, histamine, L-histidine methyl ester or carnosine were investigated. Particularly, UV spectra (300-400 nm) were recorded on solutions at various pH values, containing each binary system Cu-L; afterwards, an UV absorption spectrum for single complexes was calculated, taking into account the chemical model previously assessed, in order to fulfil a correct spectrum-structure correlation. The problem related to the eventual superimposition of the CT shoulder (approximately 330 nm) to copper(II) of OH- and imidazole pyridine nitrogen groups were now solved by means of a comparison of the UV spectra of dimer species formed by both pi-methis or tau-methis. Finally, copper(II) complex formation with 2,2'-bipyridine was taken into account to compare the behaviour of pyridine (from 2,2'-bipyridine) and pyridine imidazole nitrogens (from pi-methis or tau-methis) with respect to the UV charge transfer process to copper(II) ion.
authors.affiliation: Dipartimento di Chimica Analitica, dell'Universitá, Via Pietro Giuria 5, I-10125 Torino, Italy. enrico.prenesti@unito.it
authors.forename: Enrico
authors.initials: E
authors.lastname: Prenesti
authors.forename: Silvia
authors.initials: S
authors.lastname: Berto
authors.forename: Pier Giuseppe
authors.initials: PG
authors.lastname: Daniele
mesh_terms: D003300:Copper / Q000032:analysis* / Q000737:chemistry; D006639:Histidine / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000032:analysis* / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D013053:Spectrophotometry / Q000379:methods*; D014466:Ultraviolet Rays; D014867:Water / Q000378:metabolism
chemical_list: D007093:Imidazoles; D008024:Ligands; D014867:Water; D006639:Histidine; D003300:Copper; C029899:imidazole; C023495:N-acetylhistidine