A series of 2,3-disubstituted-tetrazole-5-thiones and 3,5-disubstituted-[1,3,4]-thiadiazole-2-thiones were synthesized by using dithizone under the best suitable reaction conditions. These two new synthetic methods feature high yield, good repeatability and easy work-up,which make them promising in industry applications.Four synthesized 2,3-disubstituted-tetrazole-5-thiones were characterized by elemental analysis, IR spectra and UV-spectra and crystal structures for the two compounds of them were also obtained. Density Functional Theory (DFT) method calculations of the optimized structure, atomic charge distributions, vibrational frequencies, electronic spectra, natural bond orbital and thermodynamic functions for the four compounds were performed and compared with their corresponding experimental results. The calculations of the second order optical nonlinearity were also carried out. All the theoretical data provid helpful information for the further studies on 2,3-disubstituted-tetrazole-5-thiones.For 2,3-diphenyl-tetrazole-5-thione, the further investigations about Mulliken and Natural populations analysis (NPA) atomic charge distributions were carried on by Hartree-Fock, DFT-B3LYP and MP2 methods using 6-31G~* 6-311G~(**) and 6-31+G~* basis sets, respectively. According to the calculated results, a new atomic charge distributions of 2,3-diphenyl-tetrazole-5-thione was proposed with the sulfur atom and tetrazole ring having negative charges and the two phenyl-rings havingpositive charges. This new resonance hybrid structure was different from the one proposed by Ogilvie et al. in 1937. Based on the new structure, physical and chemical properties of 2,3-diphenyp-tetrazole-5-thione was explained logically and protonation of 2,3-diphenyp-tetrazole-5-thione should take place not only on the S atom, but also on the N atoms having negative charges.Three synthesized 3,5-disubstituted-[1,3,4]-thiadizole-2-thiones were characterized by elemental analysis, IR spectra and UV-spectra and crystal structures for the two compounds of them were also obtained. Density Functional Theory (DFT) method calculations of the optimized structure, atomic charge distributions, vibrational frequencies, electronic spectra, natural bond orbital and thermodynamic functions for the three compounds were studied and compared with their corresponding experimental results, which were halpful for the furhter study on 3,5-disubstituted-[1,3,4]-thiadizole-2-thiones.Three metal coordination complexes with lignads containing N atom were