- The effect of carborane, bicyclo[2.2.2]octane and benzene on mesogenic and dielectric properties of laterally fluorinated three-ring mesogens
-
Six series of structurally similar compounds containing 12- and 10-vertex p-carborane (A and B), bicyclo[2.2.2]octane (C), and benzene (D) were prepared and their mesogenic and dielectric properties investigated. Comparative analysis showed that all carborane derivatives form significantly less stable mesophases than their carbocyclic analogs, however they exhibit a relatively high shielding ability for lateral fluorination. Depression of the clearing temperature upon fluorination of series 1, 3, and 5 is approximately constant for each series A-D and correlates with the diameter of the ring (the slope = 14.8 °C A-1 and R2 = 0.997). Compounds in series 2 (X = F) were used as low concentration additives to a nematic host, 6-CHBT. Dielectric parameters were extrapolated to pure additives and analyzed using the Maier-Meier equation. The Kirkwood factors g and apparent order parameters Sapp that are required to reproduce the extrapolated dielectric values follow the trend in the size of ring . The smallest g (0.47) and the largest Sapp (6.3) are obtained for carborane 2A, and the largest g (0.69) and the smallest Sapp (0.7) are obtained for the terphenyl derivative 2D. The increase of Sapp in the series D→A corresponds to the increasing disorder of the nematic solution with increasing size of ring script A sign. The Royal Society of Chemistry 2006.
- Januszko, Adam,Glab, Kristin L.,Kaszynski, Piotr,Patel, Kaushik,Lewis, Robert A.,Mehl, Georg H.,Wand, Michael D.
-
-
Read Online
- Palladium-catalyzed Suzuki cross-coupling reactions in a microemulsion
-
An enhancement of palladium-catalyzed Suzuki cross-coupling reactions between substrates possessing long-chain alkyl or oxyalkyl substituents in two-phase media, in the presence of sodium dodecylsulfate, is shown. Quantitative evaluations of the influence of SDS on the reaction rates were determined.
- Vashchenko, Valery,Krivoshey, Alexander,Knyazeva, Irina,Petrenko, Alexey,Goodby, John W.
-
p. 1445 - 1449
(2008/09/18)
-
- The Synthesis and Transition Temperatures of Some 4,4"-dialkyl- and 4,4"-Alkoxyalkyl-1,1':4',1"-terphenyls with 2,3- or 2',3'-difluoro Substituents and of their Biphenyl Analogues
-
The tetrakis(triphenylphosphine)palladium(o)-catalysed coupling of arylboronyc acids with aryl halides is used to prepare several 4,4"-dialkyl- and 4,4"-alkoxyalkyl-1,1':4',1"-terphenyls with 2,3- or 2',3'-difluoro substituents and their related biphenyl systems.Lithiation ortho to a 1,2-difluoroaromatic unit provides the route to the 2,3-difluoroarylboronic acids.The 2,3-difluoro substituted terphenyls are low-melting liquid crystals with wide-range Sc phases and no underlying smectic phase; these compounds are excellent hosts for ferroelectric systems.The compounds with widest Sc ranges are those with the difluoro substituents in an end ring and the compounds with difluoro substituents in the central ring show more nematic character and so are useful for ECB devices.
- Gray, George W.,Hird, Michael,Lacey, David,Toyne, Kenneth J.
-
p. 2041 - 2054
(2007/10/02)
-