Theoretical and experimental spectroscopic investigation of some piperazine derivatives and metal complexes

In this research, FT-IR and Raman spectra of some piperazine derivatives such as 1-cyclobutylpiperazine, 1-butylpiperazine, 1-cyclobutylpiperazine and 2-methylpiperazine have been reported in the region of 4000-30 cm-1 and 4000-50 cm-1, respectively. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments are theoretically examined by means of B3LYP density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable vibratioanl assignments have been made on the basis of potential energy distribution (PED) and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of these molecules have been predicted. Calculations are employed for four different conformations of molecules, both in gas phase and in solution. Solvent effects are investigated using chloroform and dimethylsulfoxide. All results indicate that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and the structural parameters. Vibrational frequencies, assignments and intensities are solvent dependent. Also Hofmann type host and host-guest compounds have been obtained by using 2-methylpiperazine ligand molecule. By analysing these structures with vibrational spectroscopy, it is shown that the ligand molecule was coordinated to M metal atom from nitrogen atom of 2-methylpiperazine and the guest benzen molecules were imprisoned in the structural cavities between the sheets.