Materiais moleculares funcionais contendo n-heterociclos - capes

1,4-Diaryl and Schiff’s base LC compounds 1001isotropic liquid at 139uC. The same pattern is observedon cooling.2.3. Fluorescence propertiesThese properties were only measured for compounds1,4-diaryl-[1,2,3]-triazoles Ia–e due to the very poorfluorescence of Schiff’s base derivatives IIa–c. The UVvisabsorption and fluorescence spectroscopy data inchloroform solution for compounds Ia–e are summarizedin table 2.The UV spectra of triazoles Ia–e show an intense singleband due to p–p* transitions with wavelength maximabetween 274 and 297 nm (e510 000 mol 21 cm 21 ). Thesecompounds display very weak blue emission withwavelength maxima at around 380 nm. The extensionin the conjugated system and the coplanarity, as seen incompound Ic (with a naphthyl rigid core), lead to betterresults with photoluminescence quantum (W) yields of22.8%, a moderate luminescence for electroluminescentdevice applications.Table 2. Photophysical data of 1,4-diaryl-[1,2,3]-triazolesIa–e in chloroform solution.Compound l abs /nm l em /nm a W Fluor.bIa 265 380 0.004Ib 297 386 0.074Ic 294 386 0.228Id 287 385 0.092Ie 274 380 0.005a Excitation wavelength: 290 nm.b Determined relative tostandard quinine sulphate (W Fluor 50.546).3. ConclusionsIn summary, two series of new [1,2,3]-triazole-basedliquid crystalline compounds were synthesized byapplying Cu(I)-catalysed 1,3-dipolar cycloaddition of1-azido-4-decyloxybenzene 2 to several terminal acetylenes(click-reaction). For series Ia–e, this syntheticroute yielded luminescent non-linear mesogens exhibitingmainly the SmC phase within a wide temperaturerange, as observed by optical microscopy and DSC.Luminescence properties of this series were evaluated,showing weak blue emission peaking at around 380 nm.A second series (IIa–c) comprising three non-linearcompounds containing Schiff’s base units, was preparedby functional group transformation leading to analdehyde group in the part containing the [1,2,3]-triazole, and subsequent reaction with the respectivearylamines. These compounds only exhibited the SmCphase, as observed by optical microscopy and DSC, andhad lower melting points compared with series I. Allcompounds in the two series showed a stable SmCphase and are good candidates for the design of newferroelectric materials.4. Experimental4.1. CharacterizationElemental analyses were carried out using a PerkinElmer model 2400 instrument. Infrared spectra wererecorded on a Perkin-Elmer model 283 spectrometer inKBr discs.1 H NMR spectra were obtained with aVarian Mercury Plus 400 MHz instrument using tetramethylsilane(TMS) as the internal standard. 13 C NMRspectra were recorded on a Varian Mercury Plus100 MHz spectrometer. The melting points, thermaltransitions and mesomorphic textures were determinedusing an Olympus BX50 microscope equipped with aMettler Toledo FP-82 heating stage and an exposurecontrol unit PM-30. DSC measurements were carriedout using Shimadzu equipment with a DSC-50 module.A Hitachi UV-Vis model 3000 spectrophotometer wasused to record absorption spectra. Fluorescence spectrawere recorded on a Hitachi-F-4500.4.2. MaterialsAll the reagents were obtained from commercial sourcesand used without further purification. We have recentlyreported the synthetic procedure for 1,4-diaryl derivativecompounds Ia–e [13]. The organic solvents werecommercial grade except THF (HPLC grade) and allwere dried by traditional methods. In general, all thecompounds were purified by column chromatographyon silica gel (60–120 mesh), and crystallization fromanalytical grade solvents. The purity of the sample wasconfirmed by thin layer chromatography (MerckKieselgel 60F254).4.3. Synthesis4.3.1. [1-(4-Decyloxyphenyl)-1H-[1,2,3]-triazol-4-yl]methanol,3. A mixture of 1-azido-4-decyloxybenzene 2(2.0 g, 7.26 mmol), propargyl alcohol (0.41 g,7.26 mmol), CuI (0.138 g, 0.726 mmol) and a catalyticamount of TEA in 30 ml of ethanol/water 1/1 mixturewas stirred at 70uC for 48 h. After cooling to roomtemperature, the reaction mixture was filtered, washingwith water, and the solid obtained was recrystallizedfrom hexane to give a light green powder. Yield 1.9 g(79%), m.p. 85.6uC. IR (KBr) n max /cm 21 : 3313, 3071,2919, 2850, 1522, 1255, 837. 1 H NMR (CDCl 3 ) d: 7.89(s, 1H), 7.59 (d, J58.8 Hz, 2H), 7.00 (d, J58.8 Hz, 2H),4.92 (s, 2H), 4.00 (t, J56.4 Hz, 2H), 2.37 (s, 1H), 1.79(m, 2H), 1.32 (m, 14H), 0.88 (m, 3H).