Theoretical Investigation on the Molecular Structure, Electronic, Spectroscopic Studies and Nonlinear Optical Properties of 5-bromo-1-(2-cyano-pyridin-4-yl)-1H-indazole-3-carboxylic acid diethylamide: a DFT and TD-DFT Study.

The optimized structural parameters (bond lengths and bond angles), electronic, NLO, and spectroscopic properties (FT-IR, UV¹H and ¹³C NMR) of 5-bromo-1-(2-cyano-pyridin-4-yl)-1H-indazole-3-carboxylic acid diethylamide were investigated by the B3LYP, B3PW91, and BPV86 level of theory with the 6-311++G(d,p) basis set and were compared with the experimental values. The characterization of the covalent bond was carried out with the Wiberg bond indices (WBIs) derived through the natural bond orbital analysis. The complete vibrational frequencies have been made on the basis of the potential energy distribution (PED) obtained by the Vibrational Energy Distribution Analysis 4 (VEDA4) program. Moreover, the electronic properties, such as the energies of the frontier molecular orbitals (HOMO and LUMO), energy gap (ΔELUMO-HOMO), global reactivity descriptors (global hardness, global softness, chemical potential, and electrophilicity index), absorption wavelengths (λ), excitation energies (E) and oscillator strengths (f) were performed by the time-dependent density functional theory (TD-DFT) in the chloroform solvent and gas phase. The major contributions to the electronic transitions for the UV-Vis analysis were obtained using the Gauss-Sum 2.2 program Solvent effects on NMR tensors of the title compound have been investigated at the B3LYP, B3PW91, and BPV86 levels using the chloroform solvent and gas phase The weak interaction (Van der Waals), strong attraction (hydrogen bond) and strong repulsion (steric effect) in the title compound were analyzed via the reduced density gradient (RDG) analysis using Multiwfn software. [ABSTRACT FROM AUTHOR]