Crystal Structure, Photophysical Properties, Third-Order Nonlinear Optical Response, Density Functional Theory, and...

A donor-π-acceptor conjugated dienone, (2E,4E)-5-(4-methoxyphenyl)-1-(pyridin-4-yl)penta-2,4-dien-1-one (MPP), was synthesized and characterized by spectroscopic, crystallographic, computational, and nonlinear optical techniques. Single crystal X-ray diffraction revealed that MPP crystallizes in the non-centrosymmetric monoclinic Pc space group with two crystallographically independent molecules. Hirshfeld surface analysis revealed that H···H and C···H/H···C contacts dominate the crystal packing. The compound showed an absorption maximum at 379 nm with fluorescence emission at 546 nm in solution and 586 nm in the solid state. The Z-scan measurements demonstrated negative nonlinear refraction, and a third-order nonlinear susceptibility of 4.89 × 10^-6 esu. DFT calculations disclosed a HOMO-LUMO energy gap of 3.27 eV. Molecular docking against SARS-CoV-2 main protease (6LU7) showed moderate binding affinity through hydrogen bonding and hydrophobic interactions. These findings suggest the potential of MPP as an organic material for third order nonlinear optical and optoelectronic applications.