Banana-shaped mesogens: mesomorphic properties of seven-ring esters derived from 5-chlororesorcinol

Two new homologous series of seven-ring bent-core compounds derived from 5-chlororesorcinol have been synthesized. Many of the lower homologues in both series exhibit the rectangular columnar B-1 phase. However, the three analogous compounds having long terminal alkyl chains exhibit a switchable lamellar phase, which is different from the usual B-2 phase. Although the ground state structure of the mesophase is antiferroelectric, it shows chiral conglomerates with opposite tilt and polarity. Simultaneously, racemic structures are also seen. The mesophases have been characterized using a combination of polarized light microscopy, X-ray diffraction and electro-optical studies.