Z-Isomers of Azobenzenes Highly Compatible with Liquid Crystals
作者:Christian Ruslim、Kunihiro Ichimura
DOI:10.1246/cl.1998.789
日期:1998.8
Novel guest-host liquid crystal systems containing 3,3-disubstituted azobenzenes as guests were prepared on the basis of molecular design by molecular calculations to achieve the improvement of compatibility of the chromophore with nematic phases. No phase change of nematic liquid crystals was induced by the E-to-Z photoisomerization of the guests even at doped concentrations as high as 20 wt%.
Both trans and cis isomers of azobenzene‐linked bis‐terpyridine ligand L1 were incorporated in rigid macrocycles linked by FeII(tpy)2 (tpy: terpyridine) units. The complex of the longer trans‐L1 is dinuclear [(trans‐L1)2⋅FeII2], whereas the complex of the shorter cis‐L1 is mononuclear [cis‐L1⋅FeII]. The complex cis‐L1⋅FeII was not only thermally stable but also photochemically inactive. These results
两个反式和CIS偶氮苯联双-三联吡啶配体的异构体L1在由铁联刚性大环化合物掺入II(TPY)2(:三联吡啶TPY)单元。该复合物的较长的反式- L1是双核[(反式- L1)2 ⋅的Fe II 2 ],而复杂的较短的顺式- L1是单核[顺式- L1⋅的Fe II ]。复杂的顺- L1⋅铁II不仅具有热稳定性,而且具有光化学惰性。这些结果表明顺式偶氮苯处于完全锁定状态。的稳定大环结构的顺- L1⋅铁II引起的异构化的锁定。据我们所知,这是顺式偶氮苯光和热异构化双重锁定的第一个例子。
Fusion of Photochromic Reaction and Synthetic Reaction: Photoassisted Cyclization to Highly Strained Chiral Azobenzenophanes
A method for synthesizing highly strained cyclic structures by combining photochromic and synthetic reactions is described. Tightly linked azobenzene binaphthyl dyads (R)-4 and (R)-6 could not be obtained by conventional cyclization, but continuous application of photoirradiation, which induced (E)->(Z) isomerization of the azobenzene moiety, allowed the cyclization reaction to proceed, affording the desired chiral azobenzenophanes.
CRANK, G.;MAKIN, M. I. H., AUSTRAL. J. CHEM., 1984, 37, N 4, 845-855