The molecular structure of N,N′-diformohydrazide from ab initio studies (MP2 and density functional theory) and FTIR matrix spectroscopy

Abstract

The FTIR spectrum of N,N′-diformohydrazide isolated in argon and nitrogen matrices is presented and discussed in terms of normal modes predicted by ab initio calculations. MP2/6-31G* and BLYP/6-31G* methods are applied to calculate vibrational frequencies, IR intensities and isotopic shifts of different structures of the molecule. The number of absorption bands and their frequencies for the isolated molecule differ significantly from those of N,N′-diformohydrazide in the solid state. The conformation of the undistorted molecule is different from the planar structure adopted by the molecule in the crystal and such a conformation change is proposed as the reason for the spectral differences. Ab initio calculations support this assignment and predict the vapour of N,N′-diformohydrazide to be a mixture of conformers.