Spectroscopic (Raman, FT-IR and NMR) and theoretical study of alkali metal picolinates

The FT-IR, FI-Raman and H-1 and C-13 NMR spectra of lithium, sodium, potassium, rubidium and caesium picolinates were recorded, assigned and compared in the Li -> Na -> K Rb -> Cs series and analysed. Experimental, vibrational and NMR spectra were interpreted with the aid of calculated data from density functional theory at the B3PW91/6-311++G** level. Distance, angles and dipole moments and also aromaticity indices (HOMA, EN, GEO, I-6) for the optimized structures of picolinic acid and sodium picolinate were calculated. Comparison of theoretical and experimental (x-ray) data and the application of Bader's theory enabled us to evaluate the intramolecular interactions in picolinic acid. Also, the influence of the carboxylic anion structure and the nature of metal-ligand bonding on the electronic charge distribution in the aromatic ring was investigated. The degree of perturbation in the electronic system of the ligand under the influence of metal in the Li -> Cs series was investigated with the use of statistical methods (principal component analysis) and calculated aromaticity indices. Copyright (c) 2005 John Wiley & Sons, Ltd.