Supramolecular Metallogels Research Articles

Two novel low molecular weight gelator-driven supramolecular metallogels efficient in antimicrobial activity applications.

A remarkable ultrasonication technique was successfully employed to create two novel metallogels using citric acid as a low molecular weight gelator, in combination with cadmium(ii)-acetate and mercury(ii)-acetate dissolved in N,N-dimethyl formamide at room temperature and under ambient conditions. The mechanical properties of the resulting Cd(ii)- and Hg(ii)-metallogels were rigorously examined through rheological analyses, which revealed their robust mechanical stability under varying angular frequencies and shear strains. Detailed characterization of the chemical constituents within these metallogels was accomplished through EDX mapping experiments, while microstructural features were visualized using field emission scanning electron microscope (FESEM) images. Additionally, FT-IR spectroscopic analysis was employed to elucidate the metallogel formation mechanism. Significantly, the antimicrobial efficacy of these novel metallogels was assessed against a panel of bacteria, including Gram-positive strains such as Bacillus subtilis and Staphylococcus epidermidis, as well as Gram-negative species like Escherichia coli and Pseudomonas aeruginosa. The results demonstrated substantial antibacterial activity, highlighting the potential of Cd(ii) and Hg(ii)-based citric acid-mediated metallogels as effective agents against a broad spectrum of bacteria. In conclusion, this study provides a comprehensive exploration of the synthesis, characterization, and antimicrobial properties of Cd(ii) and Hg(ii)-based citric acid-mediated metallogels, shedding light on their promising applications in combating both Gram-positive and Gram-negative bacterial infections. These findings open up exciting prospects for the development of advanced materials with multifaceted industrial and biomedical uses.

Itaconic and citraconic acid directed thixotropic and self-healable supramolecular metallogels of M(ii) (M = Co, Cu, Zn, and Cd) for the growth-inhibitory potency against human pathogenic microbes

Itaconic acid-based Co(ii), Cu(ii) and Zn(ii)-metallogels and citraconic acid-directed self-healing Cd(ii)-metallogel have been established through exploring diverse microstructural, mechanical properties and fascinating anti-pathogenic activities.

A novel supramolecular Zn(ii)-metallogel: an efficient microelectronic semiconducting device application.

A unique strategy for the synthesis of a supramolecular metallogel employing zinc ions and adipic acid in DMF medium has been established at room temperature. Rheological analysis was used to investigate the mechanical characteristics of the supramolecular Zn(ii)-metallogel. Field emission scanning electron microscopy and transmission electron microscopy were used to analyse the hexagonal shape morphological features of the Zn(ii)-metallogel. Interestingly, the electrical conductivity is observed in the electronic device with Zn(ii)-metallogel based metal-semiconductor (MS) junctions. All aspects of the metallogel's electrical properties were investigated. The electrical conductivity of the metallogel-based thin film device was 7.38 × 10-5 S m-1. The synthesised Zn(ii)-metallogel based device was investigated for its semi-conductive properties, such as its Schottky barrier diode nature.

Ni(II) supramolecular gel-derived Ni(0) nanoclusters decorated with optimal N, O-doped graphitized carbon as bifunctional electrocatalysts for oxygen and hydrogen evolution reactions

Developing bifunctional, inexpensive and scalable electrocatalyst for both oxygen and hydrogen evolution reactions (OER and HER) is of essence, considering the thrust for clean fuel hydrogen, and the association of OER with several renewable energy systems, including metal-air batteries. A systematic understanding of electrocatalysts based on the amount and speciation of heteroatom doping on the carbon matrix is fundamental to catalyst design, but remains rarely investigated. This work presents the controlled synthesis of a series of homogeneously dispersed Ni nanoclusters confined in multiple layers of heteroatom-doped graphitized carbon, from the pyrolysis of a readily preparable Ni(II)-triazole gel. The best catalyst showed superior activity requiring low overpotentials of 360 mV & 250 mV and Tafel slopes of 69 mV dec−1 & 115 mV dec−1 for OER and HER respectively, with prolonged stability under challenging electrocatalytic conditions. Judicious modulation of the type of heteroatom dopants on Ni@N,O-doped carbon redistributed the electron-density and provided additional active sites, which assisted the adsorption/desorption of OER and HER intermediates during electrocatalysis and improved electron conductivity, benefitting both OER and HER. Our results highlight a simplistic approach for the meticulous synthesis of bifunctional electrocatalysts from supramolecular metallogels, opening new horizons for designing materials for energy applications.

An organic acid consisted multiresponsive self-healing supramolecular Cu(II)-metallogel: Fabrication and analysis of semiconducting device

A remarkable strategy of a supramolecular metallogel synthesis using copper ion and succinic acid as a low molecular weight gelator (LMWG) in N,N-dimethyl formamide (DMF) medium has been developed at room temperature under ambient conditions. The mechanical property of the supramolecular copper acetate - succinic acid i.e. CuA-SA metallogel was examined by rheological study. The excellent self-healing property of CuA-SA metallogel has been recorded through thixotropic analysis. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) were used to analyse the flake-like morphological features of CuA-SA metallogel. Further, the supramolecular structure of CuA-SA metallogel exhibits electrical conductivity on a metal-semiconductor (MS) junction electronic device. The metallogel's electrical properties were extensively investigated. The metallogel based thin film device shows the electrical conductivity as 3.24 × 10−5 S.m−1. The synthesised CuA-SA metallogel based device was explored for its semi-conductive properties, such as its Schottky barrier diode-like nature.

Squaric acid driven supramolecular metallogels of Cd(II) and Zn(II): Sensitive inhibitors for multi-drug resistance ESKAPE pathogens

The article depicts the synthesis and significance of two metallogels of squaric acid implementing Cd(II) and Zn(II)-metal salts. N,N΄-dimethyl formamide has been utilised as an immobilised solvent for successive construction of metal ions directed both gel scaffolds. These metallogels exhibit an intriguing visco-elasticity which gets experimentally validated by rheological findings. Microstructural versatility with varied metal ions and EDS elemental analysis confirm the presence of all the gel-forming constituents present in the observed hierarchical morphological visualizations for both soft-scaffolds. FT-IR data indicate the considerable shifting of peaks compared to precursor gel-forming ingredients and also establish that the metallogel-development tactic might be progressed by non-covalent type supramolecular interactions. Comparative analysis of these metallogels as anti-bacterial agents against multi-drug resistive deadly pathogens including Gram-negative bacteria Escherichia coli, Salmonella typhimurium, Vibrio parahaemolyticus and Gram-positive bacteria Bacillus cereus, and Staphylococcus aureus reveals them as the potential and promising bio-functional stuffs. Thus, the bactericidal effects of Cd(II) and Zn(II) based squaric acid mediated metallogels against ESKAPE pathogens are accounted in this study.

Adipic acid directed self-healable supramolecular metallogels of Co(II) and Ni(II): intriguing scaffolds for comparative optical-phenomenon in terms of third-order optical non-linearity.

Two brilliant outcomes of supramolecular self-assembly directed, low molecular weight organic gelator based self-healable Co(II) and Ni(II) metallogels were achieved. Adipic acid as the low molecular weight organic gelator and dimethylformamide (DMF) solvent are employed for the metallogelation process. Rheological analyses of both gel-scaffolds reveal mechanical toughness as well as visco-elasticity. Thixotropic behaviours of both the gels were scrutinized. Morphological variations due to the presence of two different metal ions with diverse metal-ligand coordinating interactions were established. The mechanistic pathways for forming stable metallogels of Co(II)-adipic acid (Co-AA) and Ni(II)-adipic acid (Ni-AA) were judiciously developed through infrared absorption spectral analysis. The nonlinear optical properties, such as the third-order process, of these synthesized metallogels were scrutinized by means of the Z-scan method at a beam excitation wavelength of 750 nm by a femtosecond laser with different excitation intensities ranging from 64 to 140 GW cm-2. The third-order nonlinear optical susceptibility (χ(3)) of the order of 10-14 esu was obtained from the measured Z-scan data. Both the metallogels exhibit positive nonlinear refraction and reverse saturable (RSA) absorption at high-intensity excitation. Co(II) and Ni(II) metallogels show nonlinear refractive indices (n2I) of (3.619 ± 0.146) × 10-6 cm2 GW-1 and (3.472 ± 0.102) × 10-6 cm2 GW-1, respectively, and two photon absorption coefficients (β) of (1.503 ± 0.045) × 10-1 cm GW-1 and (1.381 ± 0.029) × 10-1 cm GW-1 at an excitation intensity of 140 GW cm-2. We also studied the optical limiting properties with a limiting threshold of 9.57 mJ cm-2. Therefore, both metallogels can be considered promising materials for photonic devices: for instance, for optical switching and optical limiting.

Building multi-color emitters with tailored lanthanide-based supramolecular metallogels

Multicomponent lanthanide-based metallogel offers unique prospects to access versatile, dynamic supramolecular soft materials with hierarchical stimuli-responsiveness and tunable functions, particularly for applications in the optical display field. In this work, a novel ligand L bearing classical coordinating terpyridine (tpy) and hosting 24-Crown-8 (24C8) moieties was synthesized with a function-oriented design principle, which further allowed the complexation between L and a series of lanthanide ions (Ln). Interestingly, several L-Ln complexes with 1:1 stoichiometry were found to be able to gel the solvent toluene/CH3CN (1:1), and thus lanthanide-based metallogels were successfully prepared. The L-Eu and L-Tb gel was found to be emissive and further utilized to produce a white light emitter through fine adjustment of stoichiometry among Eu, Tb, and L. Importantly, the multicomponent gel strategy was employed, and additional non-coordinating chromophores were introduced into the metallogel system. Thus a broad-spectrum of emission was achieved, and these multicomponent emissive gels were successfully applied as a photo printer. The metallogels also showed multiple stimuli-responsiveness such as pH, guest molecules thanks to the anchoring of predesigned functional moieties such as tpy and 24C8 on the ligand L. It is assumed that our multicomponent metallogel research shown here may open new avenues towards the design and preparation of intelligent and tunable hybrid lanthanide-based optical materials.

Exploring the studies of charge transportation of an aromatic acid based Co(II)-Metallogel scaffold fabricated Schottky device

An efficient supramolecular metallogel of Cobalt(II) has been synthesized through the ultra-sonication technique. Cobalt(II)-salt (Cobalt acetate tetrahydrate), organic acid like terephthalic acid along with N,N-dimethyl formamide solvent are the key ingredients of the Co(II)-metallogel. The rheology-based experimental values of storage and loss modulus of the Co(II)-metallogel prove the mechanical efficiency of the metallogel-material. The chemical compositions are found through elemental investigations. The infrared spectral results help to realize the metallogel formation strategy. The electrical characteristics of the synthesized metallogel have been properly investigated. The semiconducting feature of the metallogel-material has been experimentally verified. The measured current-voltage characteristics of Cobalt(II)-metallogel (Co-TA) based thin film type metal-semiconductor (MS) junction-device shows a non-linear rectifying behaviour, representing a Schottky diode (SD) performance with promising electronic charge transport property.

Hierarchical self-assembly of crown ether based metal-carbene cages into multiple stimuli-responsive cross-linked supramolecular metallogel

Hierarchical self-assembly of crown ether based metal-carbene cages into multiple stimuli-responsive cross-linked supramolecular metallogel

Carboxymethyl chitosan‒promoted luminescence of lanthanide metallogel and its application in assay of multiple metal ions

In this work, the luminescence of lanthanide supramolecular metallogel formed by the self-assembly of 5,5′,5″-(1,3,5-triazine-2,4,6-triyl)tris(azanediyl)triisophthalate (H6L) and Tb3+ was efficiently promoted by carboxymethyl chitosan (CMCS). The total quantum yield of the resultant metallogel (denoted as H6L/Tb3+/CMCS gel) was 9 times higher than the gel without CMCS. The average lifetime of H6L/Tb3+/CMCS gel increased from 0.51 ms to 1.20 ms. More importantly, the aqueous dispersion of H6L/Tb3+/CMCS xerogels showed a stable and pH-dependent luminescence. Based on the selective affinity of CMCS to different metal ions as well as with the aid of principal component analysis, H6L/Tb3+ /CMCS can be used as a sensor array to distinguish 11 metal ions (P < 0.05). This work provides a new strategy for the design and development of bio-based functional luminescent lanthanide supramolecular metallogels.

Ag-Induced metallogel based on cyclooctatetrathiophene: structural characterization and stimuli-responsive properties.

Based on saddle-shaped cyclooctathiophene (COTh) as a building block, ligands 2 and 3 were synthesized bearing 3- or 4-substituted pyridyl groups as coordination groups, which showed strong gelation abilities with AgBF4 in several solvents at room temperature. This Ag+-induced metallogel exhibited outstanding stimuli-responsive properties upon addition of halogen ions, acetonitrile or H2O.

Terephthalic acid‐directed supramolecular Cu(II)‐metallogel for photosensitive semiconducting Schottky diode with promising electronic charge transportation

SummaryTerephthalic acid‐based supramolecular metallogel of Cu(II) (ie, Cu‐TA) is developed by sonicating the mixture of copper(II) acetate monohydrate and terephthalic acid in N,N‐dimethyl formamide solvent. The rheological study is performed to expose the mechanical property of metallogel. The flake‐like morphological patterns are found through FESEM microstructural investigations. The formation strategy, crystalline nature, and thermal behavior of the Cu‐TA metallogel are also studied. The optical and electrical properties of Cu‐TA metallogel are exhaustively scrutinized, and the measured data show that Cu‐TA metallogel is semiconducting in nature. The electrical analysis indicates that the conductivity of Cu‐TA metallogel increased up to ~four times under illumination (7.49 × 10−5 S m−1) rather than the nonirradiation condition (1.83 × 10−5 S m−1). The measured I‐V characteristics of Cu‐TA metallogel‐based thin‐film metal‐semiconductor (MS) junction devices under irradiation and nonirradiation conditions show a nonlinear rectifying behavior, typical of a Schottky diode (SD).

Balancing connectivity with function in silver(i) networks of pyridyltriazole (tzpa) ligands results in the formation of a metallogel.

A new flexible and divergent 1,2,3-triazol-4-yl-picolinamide (tzpa) ligand 2 and the half-equivalent model ligand 1, both functionalised with pendant 3-pyridyl groups, are reported and their coordination behaviour with silver(i) ions is explored, both in the crystalline phase and through the formation of a supramolecular metallogel. The self-assembly of tzpa ligand 1 with AgCF3SO3 resulted in the formation of a 1D coordination polymer, binding in a bidentate fashion through the pyridyl and triazole nitrogen atoms of the tzpa binding site and a pendant pyridyl nitrogen atom of an adjacent ligand. Doubling the number of metal binding sites in ligand 2, while retaining the same metal binding domain, gives rise to the formation of a supramolecular metallogel on reaction with AgBF4 at 5 wt% in MeCN, possessing self-healing properties.

A thixotropic supramolecular metallogel with a 2D sheet morphology: iodine sequestration and column based dye separation.

Sequestration of hazardous radioactive iodine and dye separation to reduce industrial waste through reutilization is pivotal for environmental safety. In this regard, herein, the synthesis of a new waterborne ultrasensitive supramolecular metallogel (Mg@DEOA) with a 2D sheet morphology is accomplished through direct mixing of a low molecular weight gelator diethanolamine and magnesium nitrate hexahydrate. This porous metallogel (180 m2 g-1) exhibits thixotropic properties and is injectable. The material was found to be an effective (587 mg g-1) host matrix for iodine sequestration from solution. Moreover, the Mg@DEOA xerogel was used to efficiently remove rhodamine B from a mixture of dyes with high separation factors through a xerogel packed column and as an adsorbent material for water-soluble dyes and CO. This column based application demonstrated by the metallogel could be useful for practical industrial dye-separation.

Bioinspired catalysis and bromoperoxidase like activity of a multistimuli-responsive supramolecular metallogel: supramolecular assembly triggered by pi–pi stacking and hydrogen bonding interactions

We report the synthesis and characterization of a new self-assembled VO2-L metallogel. Multi-responsive properties of the gel were also studied and can be used for sensing OH− anions. Bromoperoxidase-like activity of VO2-L metallogel for oxidative bromination reaction was also reported.

Steroidal supramolecular metallogels.

The review deals with an expanding number of steroidal compounds that are capable of forming a metallogel providing a multitude of novel materials rich in their properties. The future of steroidal metallogels holds a myriad of potential applications as new intelligent materials. Detection of potentially harmful compounds without expensive instrumentation, entrapment of environmentally hazardous substances, and sensitive and selective nanomaterials represent only a few of these potential applications. This article reviews the design, synthesis, characterization, and applications of steroidal metallogels.

Vanadium(V) complex based supramolecular metallogel: self-assembly and (Metallo)gelation triggered by non-covalent and N+[sbnd]H…O hydrogen bonding interactions

Metallogel (VLG) was obtained by reaction of tridentate dibasic donor’s ligand with vanadium pentoxide in 1:1 M ratio in H2O\\DMF solution. Metallogel formation was studied using IR, UV–Visible and 1H NMR spectroscopies. Single crystal structure suitable for XRD analysis was obtained by repeated crystallization of VLG from DMF/H2O solution after few days. VLG crystallized with monoclinic P21/n space group. The ligand bonded to metal ions in tridentate dibasic fashion, together with two oxido ligand forming a square pyramidal structure. Hence, the metal ions adopted a square pyramidal geometry with slight distortion with geometrical index, τ = 0.13.

Supramolecular lanthanide metallogels rapidly formed at room temperature and their thermally stable luminescence behavior

Luminescent supramolecular metallogels based on the coordinating interaction of lanthanide ions and Fmoc-L-phenylalanine were prepared at room temperature within several seconds. The prepared metallogels exhibited strong characteristic luminescent behavior of lanthanide ions. The formation mechanism of metallogels was investigated by scanning electron microscopy, 1H NMR, FT-IR as well as UV–Vis spectroscopy. The results indicated that the formation mechanism involved the synergistic effect between lanthanide metal-ligand coordination, π-π stacking and hydrogen bonding. The prepared metallogels showed excellent thermally stable luminescence, which may be attributed to their thermally stable structure. Additionally, the reversible “on-off” luminescence effect could be achieved by alternately titrating NaOH and HCl into the metallogels. Therefore, the metallogels could be potentially used as sensors and luminescent materials.

Metal-Ion Modulated Structural Transformation of Amyloid-Like Dipeptide Supramolecular Self-Assembly.

The misfolding of proteins and peptides potentially leads to a conformation transition from an α-helix or random coil to β-sheet-rich fibril structures, which are associated with various amyloid degenerative disorders. Inhibition of the β-sheet aggregate formation and control of the structural transition could therefore attenuate the development of amyloid-associated diseases. However, the structural transitions of proteins and peptides are extraordinarily complex processes that are still not fully understood and thus challenging to manipulate. To simplify this complexity, herein, the effect of metal ions on the inhibition of amyloid-like β-sheet dipeptide self-assembly is investigated. By changing the type and ratio of the metal ion/dipeptide mixture, structural transformation is achieved from a β-sheet to a superhelix or random coil, as confirmed by experimental results and computational studies. Furthermore, the obtained supramolecular metallogel exhibits excellent in vitro DNA binding and diffusion capability due to the positive charge of the metal/dipeptide complex. This work may facilitate the understanding of the role of metal ions in inhibiting amyloid formation and broaden the future applications of supramolecular metallogels in three-dimensional (3D) DNA biochip, cell culture, and drug delivery.