Crystalline structure of BAT: dimeric moiety and extended hydrogen bond interactions. Spectroscopic and DFT calculations of several molecular models.

Compound 1-benzyl-5-amino-1H-tetrazole (BAT) was synthesized and characterized by ¹H NMR, FT–IR, and UV–Vis spectroscopies and elemental (CHNS) analysis. The crystal structure was further elucidated by single-crystal X-ray diffraction. Density functional theory (DFT) calculations with B3LYP and PBE1PBE functionals of the BAT were performed to provide structural and spectroscopic information and guide spectral assignments. The compound crystallizes in monoclinic primitive system space group P2(1)/c with a=14.91Å, b=5.12Å, c=11.19Å, V=852ų, Z=4, R₁=0.0428 at 298K. The structure exhibits intermolecular hydrogen bonds of the type N–H(amino)···N(tetrazole). Simultaneous hydrogen bonds between amino···tetrazole and tetrazole···amino establish a dimeric intermolecular structure, whereas another hydrogen bond between the remaining H atom of the amino group and the other N atoms of the tetrazole ring extends the structure into another dimension. The crystal structure of BAT is properly reproduced by DFT calculations only when a dimeric or tetrameric model is employed in the modeling. Comparisons between experimental and calculated spectral properties suggest that the monomeric form of BAT is dominant in aprotic, polar, hydrogen-bonding solvents, such as DMSO and DMF.