Two organogelators G2 and G3 with a carboxamide group have been synthesized and characterized with different spectroscopic tools. Dimethylformamide or dimethyl sulfoxide solutions of both the compounds upon the addition of a minute quantity of water show the tendency to form gels. Supramolecular self-assembly for gel formation paves the way for aggregation-induced emission enhancement (AIEE) phenomena for both the gelator molecules. Introduction of metal ions in organogels strengthens the gel property without much affecting the fluorescence behavior. However, the introduction of Ag, Fe, and Fe ions in the G2 organogel separately results in total quenching of AIEE, making it possible to sense that particular cation in the gel state. The G3 organogel shows a similar behavior with the Fe ion. Remarkably, other metallogels such as Ni(II)G2 and Co(II)G2 can sense sulfide ion and Cu(II)G2 can sense iodide ion by switching off the fluorescence even in multianalyte conditions. Furthermore, the copper-based metallogel Cu(II)G2 can be utilized as a catalyst and reaction medium for aerobic oxidation of catechol to quinone. To the best of our knowledge, this is the first attempt known so far to utilize a metallogel material for bioinspired catalysis such as catechol oxidation.

The development of metallogels widens the span of sensing activity as it opens new opportunities to develop chemosensors through metal–ligand interactions. Herein, a new nitrile-substituted 1,3,5-tricarboxamide-based gelator G4 has been fabricated and shows aggregate-induced enhanced emission (AIEE) after gelation in the presence of water. A dimethylformamide (DMF) solution of the gelator shows rapid crystallization, but addition of water to a DMF solution of gelator G4 leads to gelation at room temperature. In addition, gelator G4 was used for the formation of metallogels, and among them, the cobalt metallogel has been found to be effective for sensing l-tryptophan in the gel state through the quenching of AIEE. Interestingly, the gel is also effective in sensing bovine serum albumin protein at the nanomolar level, which contains an l-tryptophan residue. The limit of detection of Co­(II)­G4 for selective sensing of tryptophan has been found to be 2.4 × 10–8 M. To the best of our knowledge, there have been no reports to date of a metallogel being utilized to discriminate and selectively sense an amino acid and a protein. The gelation properties of the organic gelator molecule and metallogels have been explored through various spectroscopic tools and physicochemical experiments.

Finding the most effective method for cancer treatment is one of the thought-provoking tasks. Drug delivery by collapsing of metallogel to the cancer cell is an appealing way out. Cancer cells have an acidic environment due to excessive accumulation of lactic acid. In this work, the novel G5 gelator with a strategically free carboxylic acid arm has been designed and fabricated and characterized by several spectroscopic and microscopic techniques. These experiments suggest the formation of an ordered supramolecular gel with clover-leaf-like morphology. Mechanical properties from rheological measurements suggest the viscoelastic nature of the gel. Furthermore, we have obtained crystals of G5 from the pure dimethyl sulfoxide solution, whereas gelation gets induced by addition of water. This G5 gelator loses its gelation capability once the carboxylate is esterified by layering with methanol, which furnished the crystals of Me-G5′ (G5′ = G5-H). Further, the G5 gelator is used for the formation of ruthenium metallogel. Interestingly, we obtained the monomeric species [Ru­(G5′)­(η6-p-cymene)­Cl] [Ru­(II)­G5] only in confined gel space upon addition of a [Ru2(η6-p-cymene)2Cl4] dimer to G5. The Ru­(II)­G5 metallogel has an inherent anticancer property with an IC50 value of 10.53 μM for the A549 cancer cell line. Treatment of the Ru­(II)­G5 metallogel by lactic acid for mimicking the acidic environment of the malignant cell results in collapsing of the gel by releasing the ruthenium metal ion. This released ruthenium ion binds with the lactic acid derivative making the gelator G5 free and producing a new compound Ru­(II)­L, which has also shown the anticancer property. The molecular docking study revealed that the released G5 could interact with a monocarboxylate transporter to disrupt the lactate transport chain, which might induce apoptosis.

Owing to the discovery of cisplatin, a vast area of use of metallodrugs in cancer treatment was opened, but due to the side effects caused by the cisplatin complexes, researchers...

The self-healing property of metallogels resembles the innate self-healing of plant and animal biomaterials, making metallogels potential candidates for detailed studies. Tetrazoles with diverse coordination abilities and extensive H-bond formation capabilities may be able to be used as ligands to generate metallogels. In this report, four metallogels (M1G6Cl, M2G6Cl, M1G6NO 3 , and M3G6NO 3 ) based on different lanthanoids and functionalized with di­(1H-tetrazole-5-yl)­methane (H 2 G6) are designed and fabricated. All the metallogels are well characterized by different spectroscopic methods. The mechanical strengths of the metallogels are determined by rheology, and FE-SEM images reveal diverse needle-like morphologies of the metallogels after the formation of ordered self-assembled networks. All the metallogels are found to be photoluminescent in nature, with quantum yields falling in the range 0.75–0.12. The emissive nature of the gels is utilized to perform invisible photopatterning experiments, which show the potential of these metallogels to be used in confidential image or writing applications. Furthermore, the crystallization of the M3G6NO 3 metallogel in a confined gel space provides a pathway of elucidating its structure, which can be used to help predict the kinds of noncovalent interactions involved in the ordered self-assembly process. The self-healing nature of the M1G6Cl metallogels makes them the most interesting among all the gels and is further explored by the rhodamine dye-doped approach. Moreover, the low molecular weight, self-healable M1G6Cl metallogels act as unique soft materials for water purification by absorbing 98% Rhodamine B dye from water in 24 h.