Raman and Infrared Spectral Analysis, Normal Coordinate Analysis, DFT calculations of Novel Schiff Base Containing di-imine moieties

Abstract

The Raman (3500-100 cm-1) and mid-infrared (4000-400 cm-1) spectra in addition to the 1H NMR chemical shifts (δ, ppm) of ((N1Z, N4E)-N1, N4-bis (4 (dimethylamino) benzylidene) butane 1,4-diamine) Schiff base (Molecular formula, C22H30N4) has been recorded. Moreover, we have carried out full geometry optimization followed by frequency calculations using the DFTB3LYP method employing 6-31+G(d) basis set to include the polarization and diffusion functions. The Raman activities and infra intensities favour a slightly distorted symmetric molecule with an inversion center. Aided by the calculated wavenumbers assembled with Raman and infrared spectral observations, we have provided complete/reliable vibrational assignments for all fundamentals with the exception of those anticipated below 100 and 400 cm-1, respectively, this is true regardless of whether or not any fundamentals were found either overlapped or coincident. Analyses of normal coordinates provide support for the prevailing spectral interpretations, that were based on the computed atomic displacements in x, y and z Cartesian coordinate (ADCC) from B3LYP/6-31+G(d). All results are reported herein and compared with similar molecules whenever appropriate.