Ni(BIPY)(P-AA) coordination polymer: Synthesis, structural characterization, and computational insight into the optoelectronic properties

A new coordination polymer, Ni(BIPY)(P-AA), was synthesized through the solvothermal reaction of 4,4′-bipyridine, p-anisic acid, and nickel(II) acetate tetrahydrate. The resulting compound was characterized by elemental analysis, melting point determination, Fourier-transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD). Elemental analysis confirmed the proposed stoichiometric composition of the complex, while the observed change in melting point relative to the free ligands suggested successful coordination of the metal center. The FTIR spectrum of the coordination polymer showed significant shifts in characteristic vibrational bands compared with those of the uncoordinated ligands, indicating changes in the chemical environment and bonding interactions upon metal coordination. In addition, the PXRD pattern of the complex displayed new diffraction peaks together with the disappearance and shifting of characteristic reflections from the parent ligands, confirming the formation of a new crystalline phase. These findings collectively demonstrate the successful synthesis of a structurally distinct Ni(II)-based coordination polymer. Molecular properties and optical response of Ni(Bipy)(P-AA) were explored using density functional theory approach [DFT/HSE06/6–31 G(d)] to gain insight into its optoelectronic applications. The low band gap (2.85 eV), large dipole moment (10.62 D), and very high static and dynamic hyperpolarizabilities governing the electro-optic Pockels effect, second-harmonic generation, electro-optic Kerr effect, and electric-field-induced second-harmonic generation (EFISHG), which were far larger than those of the reference NLO material KH₂PO₄, with strong wavelength dependence at 1064 and 808 nm, indicate a high nonlinear optical potential of the material for optoelectronic applications. This study reveals Ni(BIPY)(P-AA) as a next-generation optoelectronic material.