Experimental and theoretical DFT studies of structure, spectroscopic and fluorescence properties of a new imine oxime derivative

Abstract

A new imine oxime, (1E,2E)-phenyl-[(1-phenylethyl)imino]-ethanal oxime (I), is synthesized and characterized. The title compound crystallizes in the monoclinic space group P2(1)/c with a = 12.3416(7), b = 9.5990(6), c = 11.9750(7), beta = 92.417(4) and Z = 4. Crystallographic, vibrational (IR), and NMR (H-1 and C-13 chemical shifts) data are compared with the results of density functional theory (DFT) method at the B3LYP/6-311++G(d,p) level. The structure of I is stabilized by intermolecular O-H center dot center dot center dot N hydrogen bonds. The theoretical calculations show that the compound exhibits a number of isomers, and the molecular geometry of the most stable optimized isomer (s-trans-E,E) can well reproduce the X-ray structure. The calculated vibrational bands and NMR chemical shifts are consistent with the experimental results. The NBO/NPA atomic charges are performed to explore the possible coordination modes of the compound. The electronic (UV-vis) and photoluminescence spectra calculated using the TD-DFT method are correlated to the experimental spectra. The DMSO solutions of I are fluorescent at room temperature. The assignment and analysis of the frontier HOMO and LUMO orbitals indicates that both absorption and emission bands are originated mainly from the pi-pi transitions.