A bis-propargyl-appended rhodamine B-based receptor BPRB has been synthesised that exhibits pronounced fluorescence enhancement in the presence of Pd2+ ions. The addition of Pd2+ enhanced the fluorescence intensity of BPRB by 113-fold (Φf = 0.37) and BPRB was found to exhibit high selectivity towards Pd2+ compared to a range of other metal ions. The enhancement of fluorescence was triggered by spirolactam ring opening followed by depropargylation of BPRB in the presence of Pd2+, as evidenced by FTIR and NMR analyses. BPRB was able to detect Pd0 without the addition of a reducing agent, and the emission intensity of BPRB–Pd0 was almost identical to that of BPRB–Pd2+; however, a rapid fluorescence response was observed in the presence of PPh3. To explore the efficiency of the rhodamine unit, a bispropargyl derivative of cyclohexane (BPCH) was synthesised and the fluorescence response towards Pd2+ was examined and compared with BPRB, revealing that the rhodamine unit enhanced the fluorescence intensity by 500-fold. The fluorescence images of BPRB and BPRB–Pd2+ samples indicate that BPRB could be useful for imaging Pd2+ in living cells.
A novel chiral monomer end-capped with a cholesteryl group and threaded with β-cyclodextrin was synthesized in order to induce the formation of a helical polymer. 1 H NMR studies revealed that one or two cyclodextrin molecules were threaded onto the synthesized chiral monomer, leading to the formation of a helical construction of self-assembled inclusion complexes. The formation of a self-assembled inclusion complex was identified using SEM and TEM. The monomeric self-assembled inclusion complex was further polymerized using benzoyl peroxide as a photoinitiator. Both the highly ordered alignment and the helical structure of self-assembled supramolecules were confirmed using polarized optical microscopy and circular dichroism spectroscopy, respectively. We have first demonstrated an easy process for the fabrication of helical polymers via self-assembled monomers threaded with a β-cyclodextrin end and capped with a chiral moiety.
A series of azobenzene monomers and related model compounds with various side-chain lengths were synthesized. The electrooptical properties of a polymer-dispersed liquid crystal (PDLC) were verified by sidechain methoxy azobenzene in various chain lengths (n ϭ 3, 6, 11). The properties under various voltages were measured and the effect of extra voltage on the transmittance of PDLC was researched as well. The experiment demonstrated the validity of employing these side chain methoxy azobenzene materials in electrooptical devices. The azobenzene model compound showed better electric-optical and thermal-optical properties, having a higher contrast ratio (CR ϭ 689) and a lower saturation voltage (4.7 V/m). All the azobenzene molecules can be photoisomerized through UV light irradiation, following the mechanism of isomerization. The reversible photo and heat isomerization property was studied. The cis-azobenzene that was transformed from the transazobenzene irradiated by UV light can decrease the clearing point of the liquid crystal phase. We used this unique characteristic to record image patterns and it worked successfully. We synthesized the azobenzene monomers can stabilize the PDLC and their relative model compounds with various alkyl chain lengths even got better electric-optical effects. We found that azobenzene monomer shows different behaviors in the electric-optical property from its relative model compound. The difference between the systems were explained using a proposed model.
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