Interaction of copper(II) with imidazole pyridine nitrogen-containing ligands in aqueous medium: a spectroscopic study.
UV (300-400 nm) and FT/IR (4000-850 cm(-1)) spectra were considered for a structural discussion of the copper(II) complexes formed with a series of imidazole-containing ligands (namely L-histidine, N-acetyl-L-histidine, histamine, L-histidine methyl ester and carnosine) in aqueous solution (T=25 degrees C, I=0.1 M). A shoulder at 330 nm was recorded for the main copper(II) complexes with all the ligands considered with the exception of carnosine: this singularity is discussed and a spectrum-structure correlation is proposed. epsilon(330) values were evaluated for CuL (59 M(-1) cm(-1)) and Cu(2)L(2)H(-2) (577 M(-1) cm(-1)) complexes with histamine and for CuL(2) (49 M(-1) cm(-1)) and CuL(3) (163 M(-1) cm(-1)) with N-acetyl-L-histidine, thus indicating the usefulness of UV spectra in the explored region for the purpose of structural definition. FT/IR spectra (recorded both in aqueous solution and on the residue of evaporated solutions of carnosine and N-acetyl-L-histidine only) help to reveal a significant conformational rearrangement of the ligand, corresponding to complex formation in solution: in fact, modifications in the fingerprint region of the FT/IR spectrum for the dimer of carnosine are observed. Indications of a copper(II)-imidazole nitrogen interaction are also obtained from FT/IR data in the 1000-1100 cm(-1) range.
Prenesti
Enrico
E
Dipartimento di Chimica Analitica dell'Università, Via Pietro Giuria 5, I-10125 Torino, Italy. prenesti@ch.unito.it
Berto
Silvia
S
D003300:Copper / Q000737:chemistry*; D004355:Drug Stability; D007093:Imidazoles / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared
D007093:Imidazoles; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D012996:Solutions; D003300:Copper