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

Shimaa Abdel Halim Hussien

doi:10.11648/j.ijctc.20190701.19

Abstract

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.

Highlights

The novel structure may be used in designing new potent and less toxic antimicrobial agents
In continuation to our previous work [22,23,24], the objective of the present study aims to the calculations of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) by using B3LYP at the 6311G(d,p) basis set to obtain geometries, electronic structures, non liner optical properties (NLO), natural bonding orbital's (NBO), UV-Vis spectra, and molecular electrostatic potential contours of the studied compounds 1– 4, these parameters characterize the forces that govern the structure of the studied compounds 1–4
They include HOMO, LUMO, energy gap (Eg), chemical hardness (η), electronegativity (X), chemical potential (V), electrophilicity (ω), electron affinity (A), ionization potential (I) and global softness (S) which are calculated at B3LYP/6-311G (d,p)

Summary

Introduction

The novel structure may be used in designing new potent and less toxic antimicrobial agents. In continuation to our previous work [22,23,24], the objective of the present study aims to the calculations of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) by using B3LYP at the 6311G(d,p) basis set to obtain geometries, electronic structures, non liner optical properties (NLO), natural bonding orbital's (NBO), UV-Vis spectra, and molecular electrostatic potential contours of the studied compounds 1– 4, these parameters characterize the forces that govern the structure of the studied compounds 1–4. The identify the extent of delocalization and the charge transfer of the electron density in the studied molecular systems by Natural bond orbital analysis (NBO) and ; extent of conjugative interaction between different subsystems of the studied compounds. The molecular electrostatic potential (MEP) of the studied molecules were explored as well

Computational Details

Electronic Structure

Global Reactivity Descriptors

Summary and Conclusion