A Multistimuli‐Responsive Photochromic Metal‐Organic Gel

Abstract

A photochromic metal-organic gel with thermo-, photo-, and anion-responsive behavior is obtained. Unusually, heating of the Al-ligand solution leads to gel formation and cooling to room temperature reverses the process to reform the solution. The gel is sensitive to weakly coordinating anions. Additionally, reversible photochromic transformations take place both in the solution and gel states, accompanied by reversibly switched luminescence.

Multi-responsive fluorescence of amphiphilic diblock copolymer containing carboxylate azobenzene and N-isopropylacrylamide

“…Environmental stimuli such as light [8], pH [9], temperature [10], humidity [11], CO 2 [12,13] and electric/ magnetic field [14] can induce conformational and/or soluble changes of segments of chains at molecular level. As one of the most famous photoresponsive chromophores, azobenzene has been widely studied in many fields, such as liquid crystal display [15], photomechanical actuators [16], light-controllable gels [17,18], holographic gratings [19], nanotechnology and photonic materials [20,21]. Nonetheless, only a few reported fluorescent properties of azobenzene-containing materials because they were virtually nonfluorescent at free state due to the high efficiency of trans-cis isomerization.…”

Gels with sense: supramolecular materials that respond to heat, light and sound

“…For example, Wei et al observed that ring closing in aluminium complexes of a dicarboxylated DTE species in alcohols produces a colour change from yellow to red, but affects neither the heat-setting of gels at 80 o C nor the dissolution of these materials on cooling to room temperature. 48 In other cases, the behaviour of the gel depends on the order in which stimuli are applied. Chen et al demonstrated that gels of a spiropyran-functionalised fibrous dendron can cycle between red emissive and yellow nonemissive states by alternating treatments with visible and UV light.…”

“…In rare cases, however, a thermoreversible gel may be obtained by raising, rather than lowering, the temperature: the gel is "heatset" and dissolves upon cooling. 29,[48][49][50][51][52][53][54][55] Reversible heat-setting is often the result of an entropically-favoured molecular transformation. For example, a metallopolymer reported by de Hatten et al forms a reversible gel at 140 o C due to a ligandexchange reaction, in which the material dissociates into free trioctylphosphine-copper(I) complexes and neutral organic polymers that can more readily aggregate.…”

Synthesis of Highly Stable Porous Metal‐Iminodiacetic Acid Gels from A Novel IDA Compound

“…[9,10] Compared with MOFs, the metal-organic gels possess poor crystallinities and unclear structures, however, they still have the following advantages: (1) The reaction can proceed at a low temperature, some materials can be obtained at room temperature; (2) the reaction time is shorter and solvent quantity is less; (3) reaction solvent is cheap and with low toxicity, the reaction can proceed in ethanol, water, N,N'-dimethylformamide (DMF), or the mixture of them; (4) the easily obtained desired shapes of the gels by utilizing various shapes of reaction containers make them more suitable for industrialized and commercial applications. Due to above points, metal-organic gels have amounts of potential applications in catalysis, [11] sensing, [12] anion recognition, [13] photophysics, [14,15] vapor adsorption, [16] separation technologies, electrochemical detection, [17] etc. Conformationally flexible ligands with amide groups [18][19][20] have been often employed to design metal-organic gels because the formed networks are able to trap solvent molecules in their crystal lattices.…”