Synthesis, transition temperatures, and optical properties of compounds with simple phenyl units linked by double bond, triple bond, ester or propiolate linkages

A series of compounds has been prepared with 4-butylsulfanylphenyl and 4-cyano- or 4-isothiocyanato-phenyl units connected by -CH=CH-, -COO-, -C=C-, or -C=C-COO- linking groups. The synthesis of the novel compounds is presented and the transition temperatures and optical parameters of the compounds are discussed and compared with those for related biphenyl reference systems. The ester linking group reduces optical and polarisability anisotropy, but the other linking groups give increased optical anisotropy (up to Delta n = 0.50) and polarisability anisotropy [up to Delta alpha = 45.2 Angstrom(3) (10(-30) m(3))].