1038806-72-2Relevant academic research and scientific papers
Induction and structural control of chiral nematic phases by the use of photoresponsive tris(?2-diketonato) Co(III) and Ru(III) complexes
Yoshida, Jun,Sato, Hisako,Hoshino, Naomi,Yamagishi, Akihiko
, p. 9677 - 9683 (2008)
Two kinds of tris(?2-diketonato) metal(III) complexes denoted as [M(acac)2(LC12)] and [M(acac)2(L azo)] (M = Ru(III) and Co(III); acac = acetylacetonato; LC 12 = 1,3-didodecyloxyphenyl-1,3-propanedionato; Lazo = 3-[4a?2-(4a?3-(butoxy)phenylazo)phenyl]-pentane-2,4-dionato) were synthesized and optically resolved into ??, ?? isomers. Here, LC 12 and Lazo were designed to be elongated perpendicular to and in parallel with the molecular C2 axis, respectively. The metal complexes were doped into three kinds of nematic liquid crystals (MBBA, EBBA, and ZLI-1132). Both dopants induced chiral nematic phases with relatively high helical twisting powers. With a purpose to clarify the mechanisms of helical induction, order parameters (S) were determined by means of polarized UV-vis measurements on nematic samples doped with racemic Co(III) complexes. As a result, the long axes of the elongated ligands in both [Co(acac) 2(LC12)] and [Co(acac)2(trans-Lazo)] were found to align in the direction of the director vector with S = 0.50 ?± 0.05 and 0.60 ?± 0.05, respectively. Based on the results, the photoresponsive behavior of ??- or ??-[Ru(acac)2(L azo)] was interpreted in terms of the variation of S accompanied with the cis-trans isomerization of the azobenzene moiety in Lazo. ? 2008 American Chemical Society.
