An analysis of the carboxylate stretching vibrations in the Cu(II)
complexes of amino acids
Baran E.J.1, Torre M.H.2
1
Universidad Nacional de La Plata, Facultad de Ciencias Exactas, Centro de Química
Inorgánica (CEQUINOR, CONICET/UNLP), La Plata, Argentina; 2Universidad de la
República, Facultad de Química, Cátedra de Química Inorgánica,
Montevideo, R.O. del Uruguay
Besides iron and zinc, copper is the most ubiquitous transition metal present in
living organisms, and is involved in a large number of important functions and
processes. Copper metalloenzymes are present in oxidases (laccases, ascorbate oxidase,
galactose oxidase, amine oxidases), participate in oxygenation and dismutation
reactions (plastocyanins, tyrosinases, superoxide dismutases) and even in oxygen
transport in arthropods and mollusks (hemocyanins).
On the other hand, copper compounds and, in particular, Cu(II) complexes
present great pharmacological interest as several of them show an important number of
effects, including anti-inflammatory, antiulcer, anticonvulsant and even anti-tumoral
activity. In this context, copper complexes of most of the simplest amino acids showed
a particular relevance, appearing even useful for copper supplementation in human and
veterinary medicine. Due to the commented importance of these complexes, since the
last ten years we have been investigating, in a systematic way, their vibrationalspectroscopic behaviour by means of IR and Raman measurements.
In this presentation the behavior of the stretching vibrations related to the
carboxylate groups of nineteen Cu(II) complexes from amino acids (aa) of general
composition Cu(aa)2 or Cu(aa)2nH2O is analyzed on the basis of the previously
reported vibrational spectroscopic data and on the structural characteristics of these
complexes.
Some general trends and tendencies are remarked and discussed. Some of the
experimentally obtained results are also analyzed on the basis of the molecular orbital
approach of Nara et al. (J. Phys. Chem. 100 (1996) 19812). In all cases, the
spectroscopic results are consistent with the monodentate binding of the COO- groups to
the metal center.
Finally, brief comments on the spectroscopic behaviour of a series of polymeric
Cu(II) complexes of dipeptides are also presented.
Keywords: Copper(II), Amino acids, Carboxylate, Stretching vibrations.
Email: baran@quimica.unlp.edu.ar