Synthesis and characterization of a three-ring bent-core compound

To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core （that is, banana-shaped） compound m-bis（4-p-octoxysryrenyl）benzene （m-OSB） and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported.^13C and ^1H NMR spectra and ^1R spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material： phase Ⅰ （T〈66℃） and phase Ⅱ （66~C〈T〈157℃）; an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombie system and P212121 space group with cell parameters of a = 7.43A°. b=6.34A°, c=72.07A°, and α=β=γ=90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-eleetrie alignment. The structure of phase Ⅱ is very similar to that of phase Ⅰ. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation （SHG）. Such characterization of the bulk material is necessary for the understanding of the growth and microstructures in the films.

Synthesis and characterization of a three-ring bent-core compound

To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core (that is, banana-shaped) compound m- bis(4- p- octoxysryrenyl)benzene (m-OSB) and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported. ¹³C and ¹H NMR spectra and IR spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material: phase I (T<66°C) and phase H (66°C12₁2₁ space group with cell parameters of a = 7.43 Å, b = 6.34 Å, c = 72.07 Å, and α = β = γ= 90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-electric alignment. The structure of phase II is very similar to that of phase I. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation (SHG). Such characterization of the bulk material is necessary for the understanding of the growth and microstructures in the films.