Molecular, spectroscopic and thermal studies on catechol, 4,5-dibromocatechol, resorcinol, hydroquinone and 4-4′-dihydroxybiphenyl derivatives armed with benzothiazole moieties

A new series of catechol, 4,5-dibromocatechol, resorcinol, hydroquinone and 4-4′-dihydroxybiphenyl derivatives possessing two benzothiazole moieties at respective positions of 1,2, 1,3, 1,4 and/or 4,4′ has successfully been synthesized. The molecular structures were fully elucidated by spectroscopic techniques (1H NMR, 13C NMR and two dimensional COSY, HMBC, HMQC, DEPT-135 and DEPT-90). The connectivity study between the cause of using different core systems in the target compounds and the anisotropic behavior as inferred from phase transition temperature and relevant morphology studies has led to some unique features arising from this series. Compounds with ortho substituent exhibit enantiotropic N and SmA phases. The analogues containing resorcinol and 4,4′-disubstituentbiphenyl show enanotiotropic nematic behavior while the hydroquinone derivative induces the formation of monotropic nematogen. An extensive study to further substantiate the relationship between the stability of the nematic phase and associated transition temperatures due to different core systems is also reported.