TD-DFT Calculations, NBO, NLO Analysis and Electronic Absorption Spectra of Some Novel Thiazolo[3,2-a]Pyridine Derivatives Bearing Anthracenyl Moiety

The electronic structure and spectra of the studied compounds 1–4 are investigated using TD-DFT/B3LYB/6-311G (d, p) level of theory. The results of calculations show that all the studied compounds 1–4 are non-planar, as indicated from the dihedral angles. The electronic absorption spectra of the studied compounds are recorded in the UV-VIS region, in both Acetone (as polar solvent) and Xylene (as non-polar solvent). The observed vertical electronic transitions assignments are facilitated via time-dependent density functional theory TD-DFT. Solvent dependence of the band maxima (λmax) and intensities of the observed spectra are explained in terms of blue and red shifts. Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The natural bond orbital (NBO) analysis were discussed in terms of the extent of delocalization, intermolecular charge transfer and second order perturbation interactions between donor and acceptor MOs. The Coulomb-attenuating method (CAM-B3LYP) and Corrected Linear Response Polarizable Continuum Model (CLR) PCM studied for theoretically obtaining the electronic absorption spectra in gas phase, Acetone and Xylene, respectively, indicate a good agreement with the observed spectra. The calculated nonlinear optical parameters (NLO); polarizibilty (α), anisotropy of the polarizibility (Δα) and first order hyperpolarizibility (β) of the studied compounds show promising optical properties. The HOMO-LUMO energy gap helped in analyzing the chemical reactivity, hardness, softness, chemical potential and electro negativity. 3D-plots of the molecular electrostatic potential (MEP) for the studied compounds are investigated and analyzed showing the distribution of electronic density of orbital's describing the electrophilic and nucleophilic sites of the selected molecules