Experimentelle Prüfung von approximativen Chiralitätsfunktionen [1, 2] am Beispiel der induziert cholesterischen Lösung chiraler Methan‐Derivate

Abstract

Die R-Cotton-Effekte von cholesterischen LBsungen, die durch chirale Methan-Derivate in nematischen Phasen induziert werden. stellen Chiralitltsbeobachtungen dar, die durch approximative Chiralitatsfunktionen in guter Naherung beschrieben werden konnen. Die untersuchten System sind Schiffsche Basen, gelost in EBBA/MBBA sowie in Licristal? Nur fur die Losung der Schiffschen Basen in EBBA/MBBA lassen sich bei Anwendung von Chiralitatsfunktionen ligandenspezifische Zahlen ermitteln.Certain chiral methane-derivatives dissolved in nematic phases induce a cholesteric structure; the measured R-Cotton-effects represent chirality observations. Approximative chirality functions serve as a competent model for the description of these observations. Here, the inducing molecules are Schitl's bases, the nematic phases LicristaP and EBBA/MBBA. Only the latter allows the calculation of ligdnd specific parameters.

Design and Synthesis of Chiral Nematic Liquid Crystals

“…This is usually achieved by addition of chiral dopants to either shorten or lengthen the pitch length (the latter is sometimes termed compensation). Questions might also be raised about how a given chiral dopant allows transfer of chirality to the phase; for optimal transfer of the twist, it is best to use a dopant that has some structural similarity with the host mixture [28][29][30][31]. • How does the pitch change with temperature?…”

“…The first step involves the FeCl 3 catalyzed coupling of (S)-(+)-2-methylbutyl bromide (10) and 4-biphenylmagnesiumbromide (formed by transmetalation from previously generated (S)-(+)-2-methylbutylmagnesiumbromide), to give the chiral biphenyl (29); this was then brominated to give (S)-(+)-4-(2-methylbutyl)-4 -bromobiphenyl (30), which was eventually cyanated using copper cyanide to give the chiral biphenyl 25. An improved synthesis of 25 was described later, applying a Kumada type coupling of 4-bromobiphenyl and (R)-2-methylbutylmagnesiumbromide to give 29 [122,123].…”