ABSTRACT
A facile approach to the design of stimuli-responsive supramolecular gels (SRSGs) termed double-metal-ion competitive coordination control is reported. By this means, the fluorescence signals and guest-selective responsiveness of the SRSGs are controlled by the competitive coordination of two different metal ions with the gelators and the target guest. To demonstrate this approach, a gelator G2 based on multiple self-assembly driving forces was synthesized. G2 could form Ca(2+) -coordinated metallogel CaG with strong aggregation-induced emission (AIE). Doping of CaG with Cu(2+) results in AIE quenching of CaG and formation of Ca(2+) - and Cu(2+) -based metallogel CaCuG. CaCuG could fluorescently detect CN(-) with specific selectivity through the competitive coordination of CN(-) with the Cu(2+) and the coordination of Ca(2+) with G2 again. This approach may open up routes to novel stimuli-responsive supramolecular materials.
Subject(s)
Calcium/chemistry , Coordination Complexes/chemistry , Copper/chemistry , Gels/chemistry , Cations, Divalent/chemistry , Coordination Complexes/chemical synthesis , Fluorescence , Gels/chemical synthesisABSTRACT
Through the rational introduction of the multi self-assembly driving forces and F(-) sensing sites into a gelator molecule, low-molecular-weight organogelators L1 and L2 were designed and synthesized. L1 and L2 showed excellent gelation ability in DMF and DMSO. They could form stable organogels (OGL1 and OGL2) in DMF and DMSO with very low critical gelation concentrations. OGL1 and OGL2 could act as anion-responsive organogels (AROGs). Unlike most of the reported AROGs showing gel-sol phase transition according to the anions' stimulation, OGL1 could colorimetrically sense F(-) under gel-gel states. Upon addition of F(-), OGL1 showed dramatic color changes, while the color could be recovered by adding H(+). Moreover, OGL1 showed specific selectivity for F(-), other common anions and cations could not lead to any similar response. What deserves to be mentioned is that the report on specific sensing of anions under gel-gel states is very scarce. The gel-gel state recognition can endow the organogel OGL1 with the merits of facile and efficient properties for rapid detection of F(-). Therefore, OGL1 could act as a F(-) responsive smart material.
ABSTRACT
An organogelator (G2) based on multi self-assembly driving forces, fluorescent signal groups and coordination binding sites was designed and synthesized. G2 could form a stable Cd(2+)-coordinated supramolecular metallogel (CdG) accompanied by strong brilliant blue aggregation-induced fluorescence emission (AIE). By the competitive coordination of Cd(2+) with gelator and I(−), the AIE of CdG could be reversibly switched "on-off-on" under gelgel states via alternative adding I(−) and Cd(2+) into CdG. Interestingly, because of the competitive coordination of Cd(2+) with I(−), the micro structure of the CdG xerogel carried out dramatic changes and formed lots of micro cavities. These micro cavities could absorb iodine vapour and caused the color of CdG xerogel change from white to brown. The CdG could not only act as a convenient high selective and sensitive I(-) detection test kit (detection limit for I(-) is 1.0 × 10(-7) M) but also as rewritable dual-channel security display materials.
ABSTRACT
By rationally introducing Ca(2+) and Fe(3+) into a supramolecular gel, a bimetal-gel CaFeG was prepared. CaFeG could reversibly "turn-on" its fluorescence upon sensing H2PO4(-) with specific selectivity under gel-gel states through the competitive coordination of Ca(2+) and Fe(3+) with gelators and H2PO4(-). Thus, CaFeG could act as a H2PO4(-) test kit and could be utilised in rewritable security display materials.