title: Polar structures of bent-core liquid crystals with tetrathiafulvalene units.
abstract: We report on a series of three bent-core liquid crystals containing tetrathiafulvalene units. Their characterization consisted of electro-optical observations, second-harmonic generation (SHG) analysis, and x-ray diffraction measurements. Compound I exhibits a lamellar optically isotropic phase on cooling from the isotropic liquid and undergoes a nonreversible field-induced transition to a birefringent state. The two others present two-dimensional structural periodicities, being only compound II switchable. Additionally, the electron density maps of compounds II and III have been obtained based on the analysis of the x-ray diffraction intensities. According to SHG measurements the ground state is antiferroelectric in the three compounds. A quite good SHG performance is found in compounds I and II.
authors.affiliation: Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Alonso
authors.forename: J
authors.initials: J
authors.lastname: Martínez-Perdiguero
authors.forename: C L
authors.initials: CL
authors.lastname: Folcia
authors.forename: J
authors.initials: J
authors.lastname: Etxebarria
authors.forename: J
authors.initials: J
authors.lastname: Ortega
authors.forename: I C
authors.initials: IC
authors.lastname: Pintre
authors.forename: M B
authors.initials: MB
authors.lastname: Ros