VIBRATIONAL STUDY OF NICOTINIC-ACID COMPLEXES WITH DIFFERENT CENTRAL IONS

Assignments are proposed for the IR and Raman spectra of potassium, zi nc and mercury(II) nicotinates and for the UV-visible spectra of the f --> f transition for erbium nicotinate. The influence of K, Zn, Hg(II ), Nd(III), Dy(III) and Er(III) on the aromatic system of nicotinic ac id was studied. There are essential differences in the number, wavenum ber and intensity of aromatic system bands in the ranges of the ring m odes, v(C=C)ar (1610-1400 cm-1), gamma(CH) (970-700 cm-1) and phi(CC) (700-650 cm-1), depending on the central ion. Potassium and mercury(II ) perturb but lanthanides stabilize the aromatic system of nicotinic a cid. The wavenumbers and intensities of some vibrational bands of the aromatic system depend systematically on the ionic potentials of the m etals.