Liquid crystals for IR: Part II synthesis and properties of perfluoroalkyl- or perfluoroalkoxy-terminated tolanes

Abstract

4-[3-fluoro-4-(trifluoromethoxy)phenyl]-2-methylbut-3-yn-2-ol 100 4-bromo-2-fluoro-1-(trifluoromethoxy)benzene 31 (388.5g -1.5mol), triethylamine TEA (218cm 3 -1.58mol), 1.8-diazabicyclo[5.4.0]undec-7-ene DBU (236cm 3 -1.58mol), PdCl2(PPh3)2 (0.3mol%), CuI (0.15mol%) and 750cm 3 of toluene were added to reaction vessel. Reaction was carried out under an N2 atmosphere. The mixture was stirred and heated up to the boiling temperature and kept under this conditions for 15 minutes. Then it was cooled down to 60 o C and a solution of 2-methylbut-3-yn-2-ol 99 (155cm 3 -1.575mol) in 300cm 3 of toluene was added dropwise and the reaction mixture was heated under reflux for 4h. When the reaction was finished resulting precipitate was filtered on a Büchner funnel. The filtrate was poured into a large amount of water and stirred for 15 minutes. Moved to a separating funnel, the layers were separated. The organic layer was washed three times with water, separated, dried with MgSO4 and solvent evaporated. Product was distilled under reduced pressure b.p. 103 o C at 0.6mmHg, yield 283g (72%). MS(EI) m/z: 262(

New-Generation Liquid Crystal Materials for Application in Infrared Region

“…As described in previous works [ 57 , 58 , 59 ] in the case of mesomorphs dedicated to infrared applications, where short perfluorinated chains are used, the presence of liquid crystalline phases is mainly related to the structure of the core itself. Functionalization in the lateral position helps to fine-tune expected parameters such as mesophase morphology, temperature range, and clearing and melting temperatures.…”

“…2-(4-(Trifluoromethoxy)phenyl)-1,3,2-dioxaborinane, 2-(3-fluoro-4 (trifluoromethoxy)phenyl)-1,3,2-dioxaborinane, and 2-(3,5-difluoro-4-(trifluoromethoxy)phenyl)-1,3,2-dioxaborinane were synthesized in our laboratory; all the details of the synthesis and purification process are described in [ 58 ]. 1-Ethynyl-4-(trifluoromethoxy) benzene, 4-ethynyl-2-fluoro-1-(trifluoromethoxy) benzene, and 5-ethynyl-1,3-difluoro-2-(trifluoromethoxy) benzene were synthesized in our laboratory; all the details of the synthesis and purification process are described in [ 57 ].…”

“…Another narrow, moderately intense absorption band at λ ~ 4.5 μm (2128 cm −1 ) was associated with the presence of the C≡C bond. However, the intensity of these vibrations changed with the anharmonicity change of the oscillator, which was the R1-C≡C-R2 system, as detailed in [ 57 ]. The different intensities of this band for different structures containing the C≡C triple bond were also directly related to the presence of fluorine atoms in positions proximal to the OCF 3 group [ 62 ].…”

“… Spectral properties in the range of 2–6 μm for selected compounds: terphenyl (in black) [ 57 ], phenyltolane (in red) [ 58 ], 13b (in blue), 18c (in green), and 5CB (in orange). …”

“…As part of our previous work [ 57 , 58 , 59 ], we developed a new molecular design approach that allowed us to obtain a next-generation self-assembling material primarily for use in the infrared range, and particularly in the MWIR range [ 60 , 61 , 62 , 63 ]. This approach involved shifting parasitic absorption bands toward longer wavelengths.…”