A series of 11 chiral dopants with an atropisomeric core derived from 4,4′-dihydroxy-2,2′,6,6′-tetramethyl-3,3′-dinitrobiphenyl were synthesized in optically pure form. These compounds were doped into five different smectic C (S C ) liquid crystal hosts to induce a ferroelectric S C * liquid crystal phase, and the reduced polarization P o was measured as a function of the dopant mole fraction x d over the range 0.005 < x d e 0.05. The polarization power δ p was found to strongly depend on the core structure of the S C host. For example, the dopant (+)-2,2′,6,6′-tetramethyl-3,3′-dinitro-4,4′-bis[(4-octyloxybenzoyl)oxy]biphenyl gave δ p values of <30 nC/cm 2 in a phenyl benzoate S C host and 1738 nC/cm 2 in a phenylpyrimidine S C host; the latter is one of the highest polarization power values reported thus far in the literature. In the phenylpyrimidine S C host, the polarization power was found to depend on the length of the dopant side chains and on the position of the atropisomeric core with respect to those of the surrounding S C host molecules, on the time average. The polarization power followed a trend opposite to that followed by the S C * helical pitch. Analysis of these results suggests that chirality transfer from the atropisomeric core of the dopant to those of the S C host molecules plays a key role in amplifying the polarization induced in the phenylpyrimidine host. It is likely that such intercore chirality transfer results in an asymmetric distortion of the S C * lattice, which in turn, further increases the conformational asymmetry of the chiral dopant by virtue of increased diastereomeric bias between the S C * lattice and the chiral conformations of the dopant.

Four new chiral dopants containing an atropisomeric biphenyl core derived from 4,4′-dihydroxy-2,2′,6,6′-tetramethylbiphenyl with different symmetry-breaking groups at the 3,3′-positions (X ) F, Cl, Br, and Me) were synthesized in optically active form. These dopants were used to induce ferroelectric SmC* liquid crystal phases in four SmC hosts with different core structures. Polarization powers δ p were measured as a function of the SmC host and compared to δ p values previously obtained for an analogous atropisomeric dopant with X ) NO 2 . Theoretical conformational analyses for rotation of the atropisomeric cores about the C-O bonds of the ester groups linking the core to the side chains were performed at the B3LYP/6-31G(d) level and used in calculating Boltzmann-weighed statistical average transverse dipole moments 〈µ ⊥ 〉 for the core-diester units. The 〈µ ⊥ 〉 values were used to normalize δ p to study the influence of the symmetry-breaking groups X on the polar ordering of the dopants. Variations in δ p(norm) are rationalized by considering models describing either achiral or chiral distortions of the zigzag binding site model of the SmC host. Results show that the symmetry-breaking groups X exert a unique influence on polar ordering of the dopants in the phenylpyrimidine host PhP1 that is consistent with a model in which chirality transfer via core-core interactions between dopant and host molecules causes a chiral distortion of the zigzag binding site.

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