Probing the chemical landscape of 3,4-dichloro-1,2,5-thiadiazole: DFT calculations and biological activity insights

Experimental and theoretical investigations were made on the molecule 3,4-dichloro-1,2,5-thiadiazole abbreviated as DCTDA. Density functional theory (DFT) approach with B3LYP functional was employed for the theoretical calculations. Geometrical optimization is performed for the molecule under DFT’s B3LYP functional and MP2 method with basis set 6-311++ G (d, p) on which the entire computational study (Molecular Electrostatic Potential [MEP], Electron localization function [ELF], Natural bond orbital [NBO], Non-Linear optical [NLO], Temperature dependent DFT [TD-DFT] calculations) is made. Spectrochemical studies involved FT-IR and UV-Visible investigations. The molecule’s chemically reactive sites have been explained via MEP andFukui function analysis. NBO analysis was done to explain the acceptor-donor interactions interference energy, and hybridization of the bond generated. Reduced Density Gradient calculations were made to analyze the non-covalent interactions within the molecule. Optical utility along with hyperpolarizability and polarizability are studied with the help of NLO analysis. Vibrational analysis included the Potential Energy Distribution assignments made by the usage of VEDA program. Frontier molecular orbital interactions were studied using the TD-DFT calculations which predicted the probable transitions. Binding of different proteins to the ligand (titled molecule) was effectively done to obtain lowest binding scores (which is found to be −4.5 kcal/mol for DCTDA) indicating to strong receptor (protein)-ligand interactions and thus deduced the very probability of the molecule being biologically active. ELF was used to explain AIM (Atom in Molecule) theory and helps visualize the localization and delocalization of electrons within the molecule. UV-Visible spectroscopy employed using TD-DFT in various solvents to study the charge transfer and the impact of different solvents on the peak position in the spectra. Thermodynamic properties such as entropy, internal energy, enthalpy, Gibb’s free energy, specific heat capacity was calculated for a wide range of temperatures. Certain local descriptors including chemical softness, chemical hardness, chemical potential and electrophilicity index were deduced using the LUMO-HOMO energy gap. Drug likeness was also deduced for DCTDA and various other of its derivatives.