Spectral Characterization and Biological Studies on Mixed Ligand Complexes of Cr(III), Ni(II) and Cu(II) Derived from 3-Aminopyridine and Nitrite Ion

Abstract

The biological activity of the aminopyridines and their transition metal complexes act as K + and Ca 2+ channel inhibitors has been discussed in the literature 1,2. 3-aminopyridine (3AP) possesses significant antiproliferative, antiinflammatory and antibacterial activities 3 and furthermore, an antitumor activity of its derivatives has also proposed 4. Metal aminopyridine complexes are generally used as asymmetric catalysts for various reactions such as hydrogenation, cyclopropanation, epoxidation etc 5. The versatile coordination modes of the ambidentate ligand nitrite ion (NO2-) were previously reported 6. Metal nitrito complexes (M-ONO) are in general used as photochemical NO precursors 7. The transition metal complexes have many applications in pharmaceutical industries, biology and medicine. They posses electrical, thermo chromic, catalytic, antibacterial and antifungal properties 8 , Metal complexes of chromium, nickel and copper have a wide range of applications such as dyes and pigments 9. Many drugs possess modified toxicological and pharmacological properties in the form of metal complexes and the most widely studied in this respect is the Cu(II) ion which has proved beneficial in many diseases such as tuberculosis, gastric ulcers, rheumatoid arthritis and cancers 10. Copper complexes are currently being investigated for their potential anticancer activity. Moreover, coordination with copper often enhances the activity of various types of drugs such as antitumor and antiinflammatory agents 11 .

Origins of optical absorption characteristics of Cu2+ complexes in aqueous solutions

“…3 These include the peak position, intensity, and the spectral width of the absorption band. 3 These include the peak position, intensity, and the spectral width of the absorption band.…”

“…For instance, Billo 5 extended notions of ligand field theory to show that the peak absorption wavelength of ligand-substituted Cu 2+ complexes follows a linear combination of ligand field strengths of the constituent equatorial ligands. 3,10 As an added advantage, Cu 2+ has only one half-filled electronic a Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, orbital ([Ar] 3d 9 ). 7 Cu 2+ complexes are extremely important as industrial colorants, 8,9 and are crucial to the functionality of a variety of biological systems and processes.…”

“…A number of parameters need to be considered for describing the optical characteristics of transition-metal complexes, as well as for revealing their probable configuration in biological settings. 3 These include the peak position, intensity, and the spectral width of the absorption band. Ligand-field theory has often been invoked to explain trends in the d-d separation arising from different chemical environments, which in turn determine the peak absorption wavelength (or energy) according to the spectrochemical series.…”

“…7 Cu 2+ complexes are extremely important as industrial colorants, 8,9 and are crucial to the functionality of a variety of biological systems and processes. 3,10 As an added advantage, Cu 2+ has only one half-filled electronic orbital ([Ar] 3d 9 ). This simplifies the description because possible transitions between multi-reference spin states can be ignored; viz., a Tanabe-Sugano diagram needs not be used.…”