Efficient Synthesis of Nicotinaldehyde-based Crystalline Organic Derivatives: Comparative Analysis between Experimental and DFT Study

The analogues of pyridine ring structures demonstrate various physiological as well as biological activities. The current research is based on experimental along with computational investigations of two new phenyl substituted nicotinaldehyde derivatives; 2-(2,4-difluorophenyl)pyridine-3-carbaldehyde (DFPPC) and 2-(2,5-dichlorophenyl)pyridine-3-carbaldehyde (DCPPC) . For structural optimization of DFPPC as well as DCPPC and to explore nonlinear optical properties, computational quantum chemical analysis was executed via density functional theory (DFT) calculations by employing M06 level with 6-311G(d,p) basis set. A consensus among theoretical (DFT) and experimental (SC-XRD) results was observed by the calculation of geometric parameters. Molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis, natural population analysis (NPA), nonlinear optical (NLO), global reactivity parameters (GRPs), and frontier molecular orbital (FMO) exploration were carried out at M06/6-311G(d,p), to comprehend hyper-conjugative interactions, electron density, electronic communications and oscillation strength. The HOMO/LUMO energy gap of DCPPC (5.108 eV) was observed to be lower than DFPPC i.e., 5.170 eV, which resulted in its higher value of global softness (0.196 Eh) along with lower global hardness (2.554 Eh) value than DFPPC. The NLO attributes of DFPPC as well as DCPPC was calculated by evaluating the total dipole moment (μtot), average linear polarizability ⟨α⟩ and second hyperpolarizability (γtot) at aforementioned level. From the NLO results, it was observed that DCPPC exhibits a higher average linear polarizability value such as 3.0772 × 10−23 esu than DFPPC i.e., 2.6116 × 10−23 esu . Whereas, higher results of γtot were observed for DFPPC i.e., 3.2455 × 10−35 than DCPPC (3.0708 × 10−35 esu). The distinguished NLO characteristics revealed that, both the chromophores (DFPPC and DCPPC) can be recognized as highly efficient NLO materials for future applications.