1,3-Disubstituted Ferrocene-Containing Thermotropic Liquid Crystals: Synthesis, Mesomorphic Properties and the Crystal and Molecular Structure

Abstract

Two families of 1,3-disubstituted ferrocene derivatives have been synthesized and their liquid-crystal behavior investigated. Compounds of series I, (η⁵-C₅H₅)Fe[(η⁵-C₅H₃)-1,3-(COOC₆H₄OOCC₆H₄OC_nH_2n+1)₂] (n = 1–14, 16, 18), exhibited remarkable mesomorphic properties. Indeed, nematic and/or smectic C phases, associated with large anisotropic domains, were observed. Derivatives of series II, (η⁵-C₅H₅)Fe[(η⁵-C₅H₃)-1,3-(COOC₆H₄OC_nH2_n+1)₂] (n = 1-9), were found to be non-mesogenic. The crystal and molecular structure of Ih (n = 8) was determined by means of X-ray analysis. The crystallographic data confirmed both a highly anisometric structure for Ih and a compact arrangement of the molecules in the crystal. The present results have shown that a critical length/depth ratio of ca. 5-7 must be passed for obtaining liquid-crystal properties.