Synthesis of 2,3-diaryltetrazole-5-thiones and theoretical studies on atomic charge distributions of 2,3-diphenyltetrazole-5-thione

Four 2,3-diaryltetrazole-5-thiones have been synthesized in high yields using a new synthetic method under mild reaction conditions. Theoretical calculations of the structure, vibrational frequencies, and natural population analysis (NPA) of atomic charge distributions on 2,3-diphenyltetrazole-5-thione 1 have been performed by DFT-B3LYP, HF, and MP2 methods using several basis sets. According to the NPA results a new resonance hybrid structure of 1 has been proposed with an exocyclic sulfur atom and a tetrazole ring carrying negative charges and two phenyl rings having positive charges. On the basis of this new proposed structure, the calculated results can explain experimental facts logically. In addition, a new chemical property of 1 has been predicted: the protonation should occur not only on the exocyclic S atom, but also on the N atoms having negative charges.