Second-order nonlinear optical properties of eight-membered centrosymmetric cyclic borasiloxanes

Abstract

<p>SHG efficiencies of eight-membered centrosymmetric cyclic borasiloxanes arise form distorted silicon atom, strong electron withdrawing group and non-covalent interactions in crystal packing.</p>

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

“…Also, we have observed puckering conformation in the eight-membered ring (Si, O, and B atoms) due to the presence of Fc substitution (Figure b) . The bond angles of boron atom, O1–B1–C13 [119.6 (3)°], O2–B2–C13 [119.8 (3)°], and O1–B1–O2 [120.7 (4)°] are close to trigonal planar, whereas the bond angle around the silicon atom is not in tetrahedral geometry; {O1–Si1–C6 [108.09 (12)°], C6–Si1–C7 [114.56 (13)°], C7–Si1–O2 [107.07 (13)°], and O2–Si1–O1 [111.03 (12)°]} indicate that the silicon atom is in the distorted environment from the regular tetrahedral geometry (Table S2), which facilitates the second-order NLO effect in the molecules. , Further, the FcBSi ( 1 ) structural parameters obtained with the DFT using the B3LYP/6-31+G** level of theory were found to be in good agreement with X-ray crystal data (Table S3). The optimized structural parameters such as bond length and bond angles are shown in Table S3.…”

“…The SHG efficiency of both FcBSi ( 1 ) and FcBSiPy ( 2 ) were measured by the Kurtz–Perry powder technique at room temperature with a uniform particle size ( 1 and 2 ) and potassium dihydrogen phosphate (KDP) as the reference material. The SHG signal of FcBSi ( 1 ) is found to be 8.0 mV (reference KDP is 20.0 mV); although 1 crystallizes in the centrosymmetric space group P 1̅, there was a surprising reflection of SHG efficiency due to the noncovalent (C–H···π) interaction, distorted silicon environment, electrostatic interaction between Fc units across the borasiloxane ring, , and unequal antiparallel packing in crystals (Figure S13), whereas FcBSiPy ( 2 ) is 1.88 times higher than FcBSi ( 1 ), which was essentially created by broken symmetry in molecule 2 , which facilities the effective charge transfer process because one boron atom is four-coordinated in the system (Figure S19). The obtained SHG result follows the same trend with the various electron-withdrawing substituted borasiloxanes that were previously reported by our group, which shows increasing electron-withdrawing nature of peripheral substitutions, and SHG efficiency is likewise increased …”

“…There are reports on different types of mono- and diferrocenyl boranes with their structures, Lewis acidity, and redox behaviours. − The reports on photophysical properties of siloxanes and boranes are known in the literature, but borasiloxanes are yet to be more explored. Recently, our group has reported the experimental and theoretical investigation of structural, ring strain, optical, and NLO properties of eight-membered centrosymmetric borasiloxanes. , The NLO activities emerged from the distorted tetrahedral environment of the silicon atom in the borasiloxane ring and noncovalent interactions in centrosymmetric crystals . Although, ferrocenyl siloxanes and cage borasiloxanes have been reported in the literature, − their optical and NLO properties have never been reported.…”

Aggregation induced emission (AIE)‐active N‐arylated ferrocenyl pyrazole‐based push–pull chromophores: Structural, photophysical, theoretical and effect of substitution on second‐order non‐linear optical properties

“…[54] The DRS UV-Vis spectrum of N-arylated ferrocenyl pyrazoles 1 and 2 exhibits strong absorption in the visible light region, and the charge transfer involving maximum absorption at 550 (1) and 585 (2) nm is due to the contribution of LMCT band; the compounds from 300 to 900 nm prove that there is absorption in most of the visible region ( Figure S15). [55] The cut-off wavelengths were observed to vary from sample to sample and were the lowest for the N-arylated ferrocene pyrazole.…”

“…The compounds can uniformly exhibit considerable first hyperpolarizability (β), which is instructive to accumulate a brief presentation of the electronic communication or charge separation between donor and acceptor (D-π-A-π-D). [55] In addition, the computed first hyperpolarizabilities of compounds 1 and 2 using B3LYP and long-range corrected functionals (CAM-B3LYP and LC-BLYP) are significantly different from each other due to the overestimates of the first hyperpolarizabilities between the donor-π-acceptor systems in B3LYP-hybrid functional, which leads to incorrect long-range charge transfer [81] (Table 3) (1) and 39.27 × 10 −30 e.s.u. (2) in LC-BLYP.…”