Columnar mesophase from a new hybrid siloxane-triphenylene

Abstract

The design, the synthesis and the mesomorphic properties of a new disc-like mesogen based on a hexasubstituted triphenylene core terminated with pentamethyldisiloxane pendant groups are reported. The siloxane fragments were grafted to the six terminal olefinic branches of a triphenylene precursor by a Pt-catalysed hydrosilylation reaction. Both the hexaolefinic and the hexasiloxane derivatives are mesomorphic, showing a rectangular columnar (Col R -p2gg) mesophase between 55 and 88 uC for the former, and a broad hexagonal (Col H -p6mm) mesophase between ambient temperature and 125 uC for the latter. The liquid crystalline behaviour was investigated by means of differential scanning calorimetry, polarised-light optical microscopy, and X-ray diffractometry. The mesophase temperature range and stability were considerably extended for the hybrid compound with respect to the siloxane-free compound. This behaviour is explained on the basis of enhanced microsegregation between the chemically distinct constituent components of the molecule.

2,3,6,7,10,11-Hexahydroxytriphenylene tetrahydrate: a new form of an important starting material for supramolecular chemistry and covalent organic frameworks

“…The closest contact distances are C9Á Á ÁC4 of 3.293 (4) Å and C9Á Á ÁC4 of 3.381 (4) Å . Experimental 2,3,6,7,10,11-Hexamethoxytriphenylene was prepared according to the literature method of Zniber et al (2002). Other chemicals were purchased from Aldrich and used as received.…”

“…Hexahydroxytriphenylene has been reported as colourless (Andresen et al, 2000;Toda et al, 2000), grey (Zniber et al, 2002) or brown (Bhalla et al, 2009). Recent reports of the synthesis of hexahydroxytriphenylene using anaerobic conditions lead one to conclude that the darker preparations are contaminated by oxidized forms of the molecule (Percec et al, 2009).…”

A columnar mesophase with high lateral order from a triphenylene-hexa(3,5-dialkoxy)benzoate

“…The starting materials, 3,5-dialkoxybenzoic acids [20] and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) [13,18,[21][22][23], have been synthesised as reported previously. Symmetric benzoate esters of triphenylene have been synthesised by reacting an acid chloride with 2,3,6,7,10,11-hexahydroxytriphenylene in the presence of pyridine or triethylamine.…”

“…It is also known that introduction of large bulky substituents causes thickening of the molecules and weakens the face-to-face interactions. This suppresses columnar phases, while the nematic phase remains relatively unaffected [17,18]. Broadening of the mesophase range is mostly achieved by frustrating the crystallisation process, thus specifically lowering the melting temperature.…”

A compact model system for electron–phonon calculations in discotic materials

“…2,3,6,7,10,11-hexakishexyloxytriphenylene (HAT6) and 2,3,6,7,10,11-hexakispropyloxytriphenylene (HAT3) and their deuterated analogues HAT6D, HAT3D were made by alkylation of 2,3,6,7,10,11-hexahydroxytriphenylene with appropriate alkylbromides in DMF in the presence of potassium carbonate [10,11]. …”