Directed Metalation Route to Ferroelectric Liquid Crystals with a Chiral Fluorenol Core: The Effect of Restricted Rotation on Polar Order
摘要:
A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a-e) or chiral fluorenol (3a-e) core were synthesized using a combined directed ortho metalation-directed remote metalation strategy. The SmC* phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C(11) fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (P(o)) values of +106 and +183 nC/cm(2), respectively, at 10 K below the SmA*-SmC* phase transition temperature. The difference in P. values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor one orientation of its transverse dipole moment along the polar axis, and to steric coupling of the core to the chiral 2-octyloxy side chain.
Directed Metalation Route to Ferroelectric Liquid Crystals with a Chiral Fluorenol Core: The Effect of Restricted Rotation on Polar Order
摘要:
A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a-e) or chiral fluorenol (3a-e) core were synthesized using a combined directed ortho metalation-directed remote metalation strategy. The SmC* phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C(11) fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (P(o)) values of +106 and +183 nC/cm(2), respectively, at 10 K below the SmA*-SmC* phase transition temperature. The difference in P. values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor one orientation of its transverse dipole moment along the polar axis, and to steric coupling of the core to the chiral 2-octyloxy side chain.
Directed Metalation Route to Ferroelectric Liquid Crystals with a Chiral Fluorenol Core: The Effect of Restricted Rotation on Polar Order
作者:J. Adam McCubbin、Xia Tong、Ruiyao Wang、Yue Zhao、Victor Snieckus、Robert P. Lemieux
DOI:10.1021/ja038920f
日期:2004.2.1
A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a-e) or chiral fluorenol (3a-e) core were synthesized using a combined directed ortho metalation-directed remote metalation strategy. The SmC* phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C(11) fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (P(o)) values of +106 and +183 nC/cm(2), respectively, at 10 K below the SmA*-SmC* phase transition temperature. The difference in P. values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor one orientation of its transverse dipole moment along the polar axis, and to steric coupling of the core to the chiral 2-octyloxy side chain.