Characterization and conformational analysis of a novel hydrazonoyltetrazole: Crystallographic and theoretical investigations of an unexpected reaction product

Abstract

A new hydrazonoyltetrazole was isolated as a byproduct from a previously reported reaction, and characterized by 1H and 13C NMR spectroscopy, infrared spectroscopy, single-crystal X-ray diffraction, and high-resolution mass spectroscopy. Intermolecular interactions in the crystal state were examined by Hirshfeld surface analysis (HSA), 2D fingerprint plots, and noncovalent interaction analysis (NCI). Geometry optimization in the gaseous phase was executed at the ωB97X-D4/def2-TZVPP level of theory, and subsequent maps of molecular electrostatic potential (MEP) were generated and analyzed. The calculated MEP was in good agreement with the HSA and NCI results. Conformational analysis was performed using a CREST/CENSO protocol. Two low-energy solution conformers were obtained. To confirm the presence of the second conformer, 1H NMR spectra were calculated, the transition state connecting the two conformers was found, and their energies were obtained with the DLPNOCCSD(T) scheme. A barrier of only 4 kcal mol-1 was found between them, and their MEP maps were also created. The dispersion energies between fragments of the three structures were calculated using the local energy decomposition (LED) scheme.