Electronic Spectra (Experimental and Simulated), and DFT Investigation of NLO, FMO, NBO, and MESP Characteristics of Some Biphenylcarboxaldehydes

Experimental UV–Visible spectral data for biphenyl-4-carboxaldehyde (B4A), biphenyl-3-carboxaldehyde (B3A), and biphenyl-2-carboxaldehyde (B2A) were obtained in the spectral space 200–400nm in a solution of CDCl3. In order to substantiate the experimental data, theoretical quantum chemical calculations were made using time-dependent DFT (TD-DFT) formalism employing B3LYP functional in combination with 6–311++G(d,p) for the three molecules in CDCl3 solution phase. Certain global reactivity descriptors were evaluated with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) (FMOs) analysis, with in the frame work of DFT/B3LYP/6–311++G(d,p) method for the three molecules being investigated. The non-linear optical (NLO) material profiles of the three molecules consisting of their static NLO parameters were theoretically investigated to find their utility for NLO applications. Hyperconjugative interactions, as revealed by natural bond orbital (NBO) analysis, helped to explain NLO behavior of the molecules in terms of intramolecular charge transfer (ICT). The reactive sites of B4A, B3A, and B2A molecules were probed by MESP surface analysis.