Furuno Yuka, Sato Hisako, Yoshida Jun, Hoshino Naomi, Fukuda Yutaka, Yamagishi Akihiko
Department of Chemistry, Faculty of Science, Ochanomizu University, Tokyo 112-8610, Japan.
J Phys Chem B. 2007 Jan 25;111(3):521-6. doi: 10.1021/jp065586b.
The linkage effects of polynuclear metal complexes on chiral induction have been studied by application of the chiral oligomers of acetylacetonato chromium(III) units as a dopant, inducing chiral nematic phases. The compounds were prepared by reacting [Cr(acac)(3)] (acac = acetylacetonato) and 1,1,2,2-tetraacetylethane (taetH(2)) in solid phase at 160 degrees C. Binuclear diastereomers were separated on a silica gel column, followed by chromatographic resolution on a chiral column packed with an ion-exchange adduct of Delta-Ru(phen)(3) (phen = 1,10-phenanthroline) and synthetic hectorite. An enantiomeric pair (DeltaDelta- and LambdaLambda-[Cr(acac)(2)(taet)Cr-(acac)(2)]) and a meso species (DeltaLambda-[Cr(acac)(2)(taet)Cr(acac)(2)]) were identified. The binuclear enantiomers were doped into a room-temperature nematic liquid crystal, N-methoxybenzylidene-4-n-butylaniline. Helical twisting power (beta(M)) was found to be +97.9 and -88.9 microm(-1) for LambdaLambda- and DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)], respectively. The values were compared with beta(M) for the monomeric enantiomers (+99.5 and -91.0 microm(-1) for Lambda- and Delta-[Cr(acac)(3)], respectively). The results are interpreted on the basis of the surface chirality model. DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)] was found to photoisomerize both in a hexane solution and in a liquid crystal phase of ZLI-1132. The quantum yield of photoisomerization in a liquid crystal phase was lowered to ca. 30% of that in a hexane solution.
通过将乙酰丙酮铬（III）单元的手性低聚物用作掺杂剂来诱导手性向列相，研究了多核金属配合物对手性诱导的连锁效应。这些化合物是通过使[Cr(acac)₃]（acac = 乙酰丙酮基）与1,1,2,2 - 四乙酰乙烷（taetH₂）在160℃下于固相中反应制备的。双核非对映异构体在硅胶柱上分离，然后在填充有Δ-[Ru(phen)₃]²⁺（phen = 1,10 - 菲咯啉）与合成锂皂石的离子交换加合物的手性柱上进行色谱拆分。鉴定出一对对映体（ΔΔ-和ΛΛ-[Cr(acac)₂(taet)Cr-(acac)₂]）和一种内消旋体（ΔΛ-[Cr(acac)₂(taet)Cr(acac)₂]）。将双核对映体掺杂到室温向列型液晶N - 甲氧基亚苄基 - 4 - 正丁基苯胺中。发现ΛΛ-和ΔΔ-[Cr(acac)₂(taet)Cr(acac)₂]的螺旋扭曲力（βM）分别为+97.9和 - 88.9 μm⁻¹。将这些值与单体对映体的βM值（Λ-和Δ-[Cr(acac)₃]分别为+99.5和 - 91.0 μm⁻¹）进行了比较。基于表面手性模型对结果进行了解释。发现ΔΔ-[Cr(acac)₂(taet)Cr(acac)₂]在己烷溶液和ZLI - 1132的液晶相中均发生光异构化。液晶相中的光异构化量子产率降至约为己烷溶液中的30％。
