Enhancement of Second-Order Nonlinear Optical Properties of Centrosymmetric Ferrocenyl Borasiloxane by a Broken-Symmetry Approach

A new eight-membered centrosymmetric ferrocenyl borasiloxane FcBSi (1) and its pyridine adduct FcBSiPy (2) were synthesized and spectroscopically characterized. Further, the compound FcBSi (1) is confirmed by single-crystal X-ray diffraction studies, which crystallizes the triclinic crystal system in the centrosymmetric space group P (1) over bar with an eight-membered ring (B2O4Si2) configuration. Both the compounds FcBSi (1) and FcBSiPy (2) exhibit a negative solvatochromism in nonpolar to polar solvents because the dipole interactions between solvent and solute molecules make high ground-state dipole moments. The time-dependent density functional theory (DFT) calculations further support the same trend with the experimental results. Second-order nonlinear optical (NLO) properties of FcBSi (1) and its four coordinated pyridine adduct FcBSiPy (2) were studied by the Kurtz and Perry powder technique. The enhanced second harmonic generation efficiency (1.88 times) and ground-state dipole moment in 2 were achieved by breaking the symmetry through the formation of four coordinated boron pyridine adduct in the solid state. Further, optical and NLO properties were supported by DFT, which revealed enhanced polarizability (alpha(0)), hyperpolarizability (beta(0)), and dipole moment (mu(tot)) in FcBSiPy (2).

Automated summary

A new eight-membered centrosymmetric ferrocenyl borasiloxane FcBSi (1) and its pyridine adduct FcBSiPy (2) were synthesized and characterized. Both compounds exhibit negative solvatochromism in nonpolar to polar solvents due to dipole interactions. DFT calculations and NLO studies support the optical and NLO properties of FcBSi (1) and FcBSiPy (2).