Detailed theoretical characterization of azo chromophores containing dicyanomethylene acceptor and various coupling components by DFT

Abstract

The structural, electronic and nonlinear optical (NLO) properties of a new series of donor-π-acceptor (D-π-A) type azo dyes bearing strong electron-accepting dicyanomethylene unit and various coupling components having different properties and conjugated through an azo linker have been investigated theoretically using Density Functional Theory (DFT) at B3LYP/631g(d). The 1H NMR chemical shifts of the dyes were calculated using GIAO method at B3LYP/6311 + g (d,p). The theoretical values of absorption maxima of the dyes were obtained by time dependent DFT using various solvents. The calculated data for 1H NMR and UV–vis were compared with the experimental ones, and the results were consistent with each other. The stabilities of the possible tautomeric forms of the compounds (I, IV, V and VI) were determined by comparison with their energies in the used solvents. The frontier molecular orbitals and the global reactivity descriptors were also computed. The computed HOMO and LUMO proved the charge transfer from the donor to the acceptor units. In addition, the NLO properties of the molecules were determined. The molecules, including strong donor and acceptor units, have a very high NLO response and may be a strong candidate as an NLO material.