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.