Synthesis, Characterization, and DFT Study of Mono- and Di-Arylated Pyridine Derivatives

The current study was performed to synthesize novel arylated pyridine derivatives viz; 2,6-bis(benzothiophen-2-yl)pyridine (PB1), 2-bromo-6-(2-bromophenyl)pyridine (PB2), 2,6-bis(2-bromophenyl)pyridine (PB3) and 2-(benzo[b]thiophen-2-yl)-6-bromopyridine (PB4), through well-known Suzuki-Miyaura Pd0-catalyzed protocol. Different characterization techniques such as UV-Visible, FT-IR, 13C-NMR, 1H-NMR, and single-crystal X-ray diffraction (SC-XRD) analysis were used for the structure elucidation of synthesized compounds. The SC-XRD results demonstrated that the crystal system of the novel compounds PB1 and PB2 was orthorhombic and monoclinic, and their space group was found to be P212121 and P21/n, respectively. The computational quantum analysis of the investigated entities was conducted using density functional theory (DFT). The geometry was optimized using the M06-2X and 6-311++G(d,p) functional. The same functional was also utilized to investigate natural bond orbitals (NBOs). At the same time, the time-dependent density functional theory (TD-DFT) was applied to examine the frontier molecular orbitals (FMOs) and the UV-Visible spectrum, which also gave Global reactivity parameters (GRPs) values. The NBO investigation proved that the stability was caused by hyper-conjugative interactions. Data from FMO and NBO were used to validate the intramolecular charge transfer (ICT) mechanisms in the compounds under study. The non-linear optical (NLO) characteristics were assessed by means of the LC-BLYP, HF, and M06-2X techniques with the 6-311++G(d,p) basis set. The analysis of NLO indicated encouraging NLO response for all the compounds that were examined.