Experimental and theoretical investigation on spectroscopic properties of some nitrogen-ended ligands

In the current dissertation, the structural, spectroscopic, and electronic properties of 1,2,4-triazole-3-carboxylic acid, 3-amino-1,2,4-triazine, and 1,2,4-triazolo-[1,5-a]pyrimidine molecules were examined. All calculations were conducted by means of DFT/ B3LYP and MP2 functionals with 6-311++G(d,p), 6-31G(d,p) and 6-311++G(d) basis sets of Gaussian 03W and GaussView programs. While the infrared spectra belonging to the molecules were recorded on 4000-400 cm-1 region, the Raman spectra were scaled on 3500-50 cm-1 region. Theoretically calculated vibrational frequencies were compared with the experimentally obtained spectra. All possible tautomer and dimer forms of the 1,2,4-triazole-3-carboxylic acid molecule in the gas phase were determined within the current study. After determining the most stable structure among those forms, geometrical parameters, vibrational frequencies, charge distributions, and HOMO and LUMO energy values of the most stable structure were theoretically calculated. Calculated vibrational frequencies and geometrical parameters were compared with experimental values. Solute-solvent interactions for 3-amino-1,2,4-triazine, and 1,2,4-triazolo-[1,5-a] pyrimidine molecules were examined under various medium by applying PCM (Polarizable Continuum Model) method at the DFT B3LYP/6-311++G(d,p) level. These examinations were optimized through B3LYP/6-311++G(d,p) method by determining all possible tautomers and isomers of the both molecules in the gas phase. Following to optimization of both forms in the gas phase, these structures were optimized by using SCRF method in various solvents. Additionally, optimized structures were utilized to examine solvent effects on geometrical parameters, vibrational frequencies, dipole moment and charge distributions.