Synthesis, spectroscopic, and DFT quantum chemical studies of 3- and 4-pyridylacetonitriles

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The compounds 3-Pyridylacetonitrile (3PAN) and 4-Pyridylacetonitrile (4PAN) have been synthesized by cyanation of 3 and 4-bromo methyl pyridines with TMSiCN under basic conditions. The synthesized molecules 3PAN and 4PAN were distinguished by FTIR, FT-Raman, NMR and density functional theory (DFT) computations. The ground state structure of the molecules were determined by evaluating torsional potential energies as a function of angle of rotation around CC bonds of functional groups by DFT method B3LYP level with 6–311++G (d,p) basis set. All the vibrational modes of the molecule are assigned unambiguously utilizing potential energy distribution (PED) procure in the DFT computations. The rms error between the experimental and scaled calculated frequencies of 3PAN and 4PAN were obtained as 7.20 and 6.67 cm−1. The first order hyperpolarizability, polarizability and dipole moment values are evaluated to study the NLO response of the molecules under examination. The HOMO-LUMO orbital energy gap and thermodynamic parameters are also determined. The molecular electrostatic potential (MESP) is mapped to obtain the charge density distribution. The 13C and 1H NMR chemical shifts of the compounds are studied by the gauge independent atomic orbital (GIAO) procedure and correlate with experimental observed results. NBO analysis is made to study the stability of the molecule arising from charge delocalization and hyper conjugative interactions. The UV–Visible spectra have been calculated using TD-DFT procedure theoretically to know the type of electronic transitions involved in titled compounds and Fukui functions were also studied for 3PAN and 4PAN.