Synthesis and physical properties of ferrocene derivatives XXIV: structural study of liquid crystalline mono-substituted ferrocene derivatives

Abstract

Crystal structures of mono-substituted ferrocene derivatives,ω-[4-(4-methoxyphenoxycarbonyl)phenoxy]alkoxycarbonyl ferrocene (mMAF-n, n = 3-8, 11, where n is the number of carbon atoms in the alkyl spacer), are newly determined. The molecular structures of mMAF-n are divided into three groups; (i) a bent shape containing a doublegauche conformation (n = 2, 4, 6), (ii) a linear shape containing a kink (n = 3, 5, 7), and (iii) an extended linear shape adopting an all-trans conformation (n = 8, 11). The difference of the molecular shape between group (i) and (ii) is highly correlated with the parity of the number of carbon atoms in the alkyl spacer (odd-even effects). In both group (i) and (ii), the high entropic contribution of gauche conformations is introduced in the alkyl spacer, which is consistent with the non-liquid crystallinity of mMAF-n (n = 2-7). In group (iii), it is found out that there is a border at mMAF-8 on the mesomorphism of mMAF-n (n = 2-12).