A comparative molecular structure – NLO activity study of ortho-bridged dibenzaldehydes: Synthesis, crystal structure, SHG, and DFT studies.

• The origin of structure driven NLO activity of 2,2′-[1,2-phenylene-bis(methylenoxy)]- dibenzaldehyde with non-linear o -xylenyloxy linker is demonstrated in comparison with three other dibenzaldehydes with linear linkers. • Single crystal XRD, UV-Vis-NIR spectroscopy, DFT, and SHG studies rationalize their linear and nonlinear optical properties. • A comparative molecular structure-NLO activity relationship of four o -bridged dibenzaldehydes is investigated from computational and experimental studies. Structural and second order nonlinear optical characteristics of four ortho -bridged dibenzaldehydes with alkyloxy- and xylenyloxy linkers are compared from the XRD, UV-Vis-NIR spectroscopic, SHG, and DFT studies. Interruption of electron polarization by π -conjugation of the linkers between the two benzaldehyde units affect their NLO properties like hyperpolarizability (β) in these acceptor– π –bridge–donor– π –bridge–acceptor (A– π –D– π –A) systems. The noncentrosymmetric 2,2′-[1,2-phenylenebis(methylenoxy)]dibenzaldehyde exhibits SHG efficiency matching with that of potassium dihydrogenphosphate (KDP) in Kurtz-Perry powder method. The acentric supramolecular architecture stabilized by H-bonding and aromatic π - π stacking interactions in the solid state with the non-linear o -xylenyloxy linker rationalizes the origin of its structure driven NLO property. Chromophore density, broad optical transparency, low cut-off wavelength of electronic absorptions, and thermal stability of 2,2′-[1,2-phenylenebis(methylenoxy)]dibenzaldehyde make it a promising candidate for second order NLO applications. [Display omitted] Conjugation interrupted ortho -bridged dibenzaldehyde exhibits NLO activity due to inductive and steric effects, acentric supramolecular packing in the solid state, broad optical transparency, low cut off wavelength of electronic absorption, and thermal stability. [ABSTRACT FROM AUTHOR]