A Multi-Redox Responsive Cyanometalate-Based Metallogel

Efficient antimicrobial applications of two novel supramolecular metallogels derived from a l(+)-tartaric acid low molecular weight gelator

Novel metallogels were synthesized using l(+)-tartaric acid as a gelator, along with cadmium(ii)-acetate and mercury(ii)-acetate in N,N-dimethyl formamide at room temperature. Rheological analyses confirmed the mechanical stability of Cd(ii)- and Hg(ii)-metallogels under varying conditions. Characterization through EDX mapping and FESEM imaging provided insights into their chemical constituents and microstructural features. FT-IR spectroscopy elucidated the metallogel formation mechanism. Antimicrobial assays revealed significant activity against various bacteria, including Gram-positive and Gram-negative strains. This study presents a comprehensive exploration of Cd(ii) and Hg(ii)-based l(+)-tartaric acid-mediated metallogels, highlighting their potential in combating bacterial infections. These findings suggest promising applications in both industrial and biomedical fields, offering avenues for the development of advanced materials.

Novel supramolecular luminescent metallogels containing Tb(iii) and Eu(iii) ions with benzene-1,3,5-tricarboxylic acid gelator: advancing semiconductor applications in microelectronic devices

A novel strategy was employed to create supramolecular metallogels incorporating Tb(iii) and Eu(iii) ions using benzene-1,3,5-tricarboxylic acid (TA) as a gelator in N,N-dimethylformamide (DMF). Rheological analysis demonstrated their mechanical robustness under varying stress levels and angular frequencies. FESEM imaging revealed a flake-like hierarchical network for Tb-TA and a rod-shaped architecture for Eu-TA. EDX analysis confirmed essential chemical constituents within the metallogels. FT-IR, PXRD, Raman spectroscopy, and thermogravimetric analysis assessed their gelation process and material properties, showing semiconducting characteristics, validated by optical band-gap measurements. Metal-semiconductor junction-based devices integrating Al metal with Tb(iii)- and Eu(iii)-metallogels exhibited non-linear charge transport akin to a Schottky diode, indicating potential for advanced electronic device development. Direct utilization of benzene-1,3,5-tricarboxylic acid and Tb(iii)/Eu(iii) sources underscores their suitability as semiconducting materials for device fabrication. This study explores the versatile applications of Tb-TA and Eu-TA metallogels, offering insights for material science researchers.

Rapid Semiconducting Supramolecular Mg(II)-Metallohydrogel: Exploring Its Potential in Nonvolatile Resistive Switching Applications and Antiseptic Wound Healing Properties

An effective strategy was employed for the rapid development of a supramolecular metallohydrogel of Mg(II) ion (i.e., Mg@PEHA) using pentaethylenehexamine (PEHA) as a low-molecular-weight gelator in aqueous medium under ambient conditions. The mechanical stability of the synthesized Mg@PEHA metallohydrogel was characterized by using rheological analysis, which showed its robustness across different angular frequencies and oscillator stress levels. The metallohydrogel exhibited excellent thixotropic behavior, which signifies that Mg@PEHA has a self-healing nature. Field emission scanning electron microscopy and transmission electron microscopy images were utilized to explore the rectangular pebble-like hierarchical network of the Mg@PEHA metallohydrogel. Elemental mapping through energy-dispersive X-ray spectroscopy analysis confirmed the presence of primary chemical constituents in the metallohydrogel. Fourier transform infrared spectroscopy spectroscopy provided insights into the possible formation strategy of the metallohydrogel. In this work, Schottky diode structures in a metal-semiconductor-metal geometry based on a magnesium(II) metallohydrogel (Mg@PEHA) were constructed, and the charge transport behavior was observed. Additionally, a resistive random access memory (RRAM) device was developed using Mg@PEHA, which displayed bipolar resistive switching behavior at room temperature. The researchers investigated the switching mechanism, which involved the formation or rupture of conduction filaments, to gain insights into the resistive switching process. The RRAM device demonstrated excellent performance with a high ON/OFF ratio of approximately 100 and remarkable endurance of over 5000 switching cycles. RRAM devices exhibit good endurance, meaning they can endure a large number of read and write cycles without significant degradation in performance. RRAM devices have shown promising reliability in terms of long-term performance and stability, making them suitable for critical applications that require reliable memory solutions. Significant inhibitory activity against the drug-resistant Klebsiella pneumonia strain and its biofilm formation ability was demonstrated by Mg@PEHA. The minimum inhibitory concentration value of the metallohydrogel was determined to be 3 mg/mL when it was dissolved in 1% DMSO. To study the antibiofilm activity, an MTT assay was performed, revealing that biofilm inhibition (60%) commenced at 1 mg/mL of Mg@PEHA when dissolved in 1% DMSO. Moreover, in the mouse excisional wound model, Mg@PEHA played a crucial role in preventing postoperative wound infections and promoting wound healing.

Exploration of a wide bandgap semiconducting supramolecular Mg(II)-metallohydrogel derived from an aliphatic amine: a robust resistive switching framework for brain-inspired computing

A rapid metallohydrogelation strategy has been developed of magnesium(II)-ion using trimethylamine as a low molecular weight gelator in water medium at room temperature. The mechanical property of the synthesized metallohydrogel material is established through the rheological analysis. The nano-rose like morphological patterns of Mg(II)-metallohydrogel are characterized through field emission scanning electron microscopic study. The energy dispersive X-ray elemental mapping analysis confirms the primary gel forming elements of Mg(II)-metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic study. In this work, magnesium(II) metallohydrogel (Mg@TMA) based metal-semiconductor-metal structures have been developed and charge transport behaviour is studied. Here, it is confirmed that the magnesium(II) metallohydrogel (Mg@TMA) based resistive random access memory (RRAM) device is showing bipolar resistive switching behaviour at room temperature. We have also explored the mechanism of resistive switching behaviour using the formation (rupture) of conductive filaments between the metal electrodes. This RRAM devices exhibit excellent switching endurance over 10,000 switching cycles with a large ON/OFF ratio (~ 100). The easy fabrication techniques, robust resistive switching behaviour and stability of the present system makes these structures preferred candidate for applications in non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics etc.

A 5-aminoisophthalic acid low molecular weight gelator based novel semiconducting supramolecular Zn(ii)-metallogel: unlocking an efficient Schottky barrier diode for microelectronics

A novel method has been successfully developed for creating supramolecular metallogels using zinc(ii) ions and 5-aminoisophthalic acid as the gelator (low molecular weight gelator) in a dimethylformamide (DMF) solvent at room temperature. Comprehensive rheological investigations confirm the robust mechanical strength of the resulting zinc(ii)-metallogel. Microstructural analysis conducted through field-emission scanning electron microscopy (FESEM) unveils a unique flake-like morphology, with energy-dispersive X-ray (EDX) elemental mapping confirming the prevalence of zinc as the primary constituent of the metallogel. To understand the formation mechanism of this metallogel, Fourier-transform infrared (FT-IR) spectroscopy was employed. Notably, these supramolecular zinc(ii)-metallogel assemblies exhibit electrical conductivity reminiscent of metal-semiconductor (MS) junction electronic components. Surprisingly, the metallogel-based thin film device showcases an impressive electrical conductivity of 1.34 × 10-5 S m-1. The semiconductor characteristics of the synthesized zinc(ii)-metallogel devices, including their Schottky barrier diode properties, have been extensively investigated. This multifaceted study opens up a promising avenue for designing functional materials tailored for electronic applications. It harnesses the synergistic properties of supramolecular metallogels and highlights their significant potential in the development of semiconductor devices. This work represents a novel approach to the creation of advanced materials with unique electronic properties, offering exciting prospects for future innovations in electronic and semiconductor technologies.

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.

Recent advances in the development of europium(III) and terbium(III)-based luminescent supramolecular metallogels

In the recent past, special attention has been paid to the development of metallogels as novel luminescent materials from rationally designed gelators with lanthanide ions, especially europium (Eu(III)) and terbium (Tb(III)) metal ions. Lanthanide (Ln(III)) based metallogels possess various useful properties with an extensive range of applications in the field of advanced materials, and electronic and bio-technologies. Lanthanide ions in coordination with appropriate sensitizer ligands can reproduce metal-based optical, redox, and electronic properties in soft gel materials. The optical properties of the luminescent Ln(III) based metallogels can be tuned over the complete visible spectrum (400-750 nm) including the generation of white light by mixing both Eu(III) and Tb(III) with the ligand in various stoichiometric ratios. Additionally, the dynamic nature of the lanthanide-ligand (Ln-N) coordination bond allows the Ln(III) based metallogels to respond to various external stimuli. Luminescent self-healing supramolecular gels using organic ligands as 'hosts' and Ln(III) ions as 'guests' are also a current topic of research interest. In this review, we discuss and summarize some selected recent examples of newly developed luminescent Eu(III) and Tb(III) based supramolecular metallogels with potential applications in the fields of optoelectronic devices, stimuli responsiveness, self-healing, luminescent films, and sensors.

A "heat set" Zr-Diimide based Fibrous Metallogel: Multiresponsive Sensor, Column-based Dye Separation, and Iodine Sequestration

Sensing and monitoring hazardous contaminants in water and radioactive iodine sequestration is pivotal due to their detrimental impact on biological ecosystems. In this context, herein, a water stable zirconium-diimide based metallogel (Zr@MG) with fibrous columnar morphology is accomplished through the "heat set" method. The presence of diimide linkage with long aromatic chain manifests active luminescence properties in the linker as well as in the supramolecular framework structure. The as-synthesized Zr@MG xerogel can selectively detectCr₂O₇^2- (LOD = 0.52 ppm) and 2,4,6-trinitrophenol (TNP) (LOD = 80.2 ppb) in the aqueous medium. The Zr@MG paper strip-based detection for Cr₂O₇^2- and nitro explosive makes this metallogel reliable and an attractive luminescent sensor for practical use. Moreover, a column-based dye separation experiment was performed to show selective capture of positively charged methylene blue (MB) dye with 98 % separation efficiency from the mixture of two dyes. Also, the Zr@MG xerogel showed effective iodine sequestration from the vapor phase (232 wt%).

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.

A croconate-directed supramolecular self-healable Cd(II)-metallogel with dispersed 2D-nanosheets of hexagonal boron nitride: a comparative outcome of the charge-transport phenomena and non-linear rectifying behaviour of semiconducting diodes

The use of croconic acid disodium salt (CADS) as an organic gelator with Cd(II) salt to obtain an efficient soft-scaffold supramolecular self-healable metallogel (Cd-CADS) in N,N-dimethyl formamide (DMF) media was investigated following an ultrasonication technique. The experimentally scrutinized rheological values of the fabricated metallogel not only revealed the visco-elastic property and mechanical stiffness, but also exposed the self-healable behaviour of the gel material. Two-dimensional (2D) nanosheets of hexagonal boron nitride (h-BN) were incorporated within the gel network to obtain a 2D nanosheet dispersed metallogel of Cd(II) croconate (h-BN@Cd-CADS). The microstructural investigations of the original gel network and hexagonal boron nitride (h-BN) 2D nanosheet dispersed gel-network were performed through field emission scanning electron microscopy (FESEM) and established the interconnecting rod-like fibrous type morphological patterns and inter-connected hexagonal type rod-shaped architecture pattern, respectively. High resolution transmission electron microscopy (HRTEM) was used to visualize the morphological distinction of the Cd-CADS metallogel with the h-BN 2D nanosheets. The infrared spectral (FT-IR) outputs helped to identify the formation pathway to construct the semi-solid self-healing flexible metallogel and h-BN 2D nanosheet dispersed metallogel nanocomposite, respectively. Fascinating electronic-charge transportation was revealed in the as-fabricated Cd-CADS and h-BN@Cd-CADS metallogel-based devices. Furthermore, h-BN 2D-nanosheet-directed modulation of the non-linear rectifying feature of the supramolecular Cd-CADS-metallogel was observed, with the h-BN@Cd-CADS metallogel showing a greater rectifying property, implying that it has a higher conductivity compared to the Cd-CADS metallogel.

A multistimulus-responsive self-healable supramolecular copper(ii)-metallogel derived from l-(+) tartaric acid: an efficient Schottky barrier diode

A low molecular weight gelator l-(+) tartaric acid- based self-healing supramolecular Cu(ii)-metallogel offers an electronic device of Schottky barrier diode at room temperature.

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.

4,4′-Bipyridine-based Ni(ii)-metallogel for fabricating a photo-responsive Schottky barrier diode device

4,4′-Bipyridine-based Ni(ii)-metallogel has been implemented to execute a light-responsive semiconducting Schottky barrier diode device with advanced functionality.

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.

Copper-based metal-organic xerogels on paper for chemiluminescence detection of dopamine

In this work, copper(ii)-containing metal-organic xerogels (Cu-MOXs), which were composed of copper as the central ion and 2,2'-bipyridine-6,6'-dicarboxylic acid as the ligand, were quickly synthesized by a mild facile strategy. The Cu-MOXs exhibited superior catalytic performance for the luminol-H₂O₂ chemiluminescence (CL) system. The possible mechanism was studied via CL spectra, UV-Vis absorption and electron paramagnetic resonance (ESR). Since dopamine (DA) can inhibit the reaction of this system, a sensitive paper-based CL device for the detection of DA was established. Under the optimal experimental conditions, the linear range of this method was 40-200 nM with a detection limit of 10 nM. The proposed method was used for the determination of DA in urine samples.

Tunable Metallogels Based on Bifunctional Ligands: Precursor Metallogels, Spinel Oxides, Dye and CO2 Adsorption

A semisolid gel material is a gift of serendipity via various chemical interactions, and metal incorporation (metallogels) imparts diverse functional properties. In this work, we have synthesized four metallogels from tetrapodal and hexapodal carboxylic acid/amide-based low-molecular-weight gelators with Ni(II) and Cu(II) salts. These metallogels can be tuned to be a low-temperature precursor of porous spinel oxides. These xerogels exhibit impressive water soluble dye and carbon dioxide adsorption, which coupled with the tunability and facile synthesis of porous spinel oxides underscores their potential in environmental remediation and energy applications.

Recent advances in coordination-driven polymeric gel materials: design and applications

Recently, research attention has been directed towards the coordination driven synthesis of gels, including coordination polymer gels (CPGs) and metal-organic cage based gels, which have shown applications in diverse fields, including optoelectronics, catalysis, sensing, gas-storage, and self-healing. A wide variety of CPGs and metal-organic cage based gels have been reported, to date, by choosing the right combination of metal ions and rationally designed organic linkers. In this article, we focused on recent developments in CPGs and metal-organic cage based gels and their applications.

Self-healing, luminescent metallogelation driven by synergistic metallophilic and fluorine-fluorine interactions

Square planar platinum(ii) complexes are attractive building blocks for multifunctional soft materials due to their unique optoelectronic properties. However, for soft materials derived from synthetically simple discrete metal complexes, achieving a combination of optical properties, thermoresponsiveness and excellent mechanical properties is a major challenge. Here, we report the rapid self-recovery of luminescent metallogels derived from platinum(ii) complexes of perfluoroalkyl and alkyl derivatives of terpyridine ligands. Using single crystal X-ray diffraction studies, we show that the presence of synergistic platinum-platinum (PtPt) metallopolymerization and fluorine-fluorine (FF) interactions are the major driving forces in achieving hierarchical superstructures. The resulting bright red gels showed the presence of highly entangled three-dimensional networks and helical nanofibres with both (P and M) handedness. The gels recover up to 87% of their original storage modulus even after several cycles under oscillatory step-strain rheological measurements showing rapid self-healing. The luminescence properties, along with thermo- and mechanoresponsive gelation, provide the potential to utilize synthetically simple discrete complexes in advanced optical materials.

Triethylenetetramine-Based Semiconducting Fe(III) Metallogel: Effective Catalyst for Aryl-S Coupling

A fascinating way to originate a mechanically stable metallogel of ferric ions with metal-coordinating organic ligand triethylenetetramine through direct mixing of their water solutions in a stoichiometric ratio is achieved under ambient conditions. The rheological study established the mechanical property of the Fe(III) metallogel. A cashew-shaped microstructure of the metallogel was observed by FESEM analysis. The electrical property of the Fe(III) metallogel was also carefully scrutinized. The semiconducting features like the Schottky barrier diode property of the Fe(III) metallogel were explored. The catalytic role of the Fe(III) metallogel was also critically explored. The Fe(III) metallogel shows an excellent catalytic property toward the synthesis of aryl thioethers via a C-S coupling reaction under mild reaction conditions without the use of any organic solvent.

Gel Formed by Self-Assembly of a Urea-Modified Monopyrrolotetrathiafulvalene Derivative Displays Multi-Stimuli Responsiveness and Absorption of Rhodamine B

A new monopyrrolotetrathiafulvalene-based derivative containing a urea group was designed, synthesized and thoroughly characterized. It proved to be a non-gelator in a single solvent even when heated or sonicated. However, it could self-assemble in a CHCl₃ (CH₂ Cl₂ )/n-hexane mixture to form a thermo-responsive supramolecular organogel. SEM, FT-IR spectroscopy, UV/Vis absorption spectroscopy, and SAXS revealed that in the organogel system, the gelators self-assembled into supramolecular networks with a J-type aggregation mode under the joint effect of π-π stacking, intermolecular hydrogen-bonding, and van der Waals forces. Interestingly, the gel phase was shown to undergo reversible gel-sol transformation induced by Fe³⁺ -Vitamin C (Vc), trifluoroacetic acid-triethylamine (TFA-TEA) and picric acid (PA)-NaOH. In particular, in the presence of picric acid, the experimental results proposed that charge transfer occurred from the electron-donor gelator to the electron-acceptor picric acid due to the possibility of complex formation. Furthermore, the formed organogel could behave as the matrix for encapsulating cationic fluorescent dye from wastewater, and the adsorption efficiency was directly proportional to the concentration of the gelator.

Instant hydrogel formation of terpyridine-based complexes triggered by DNA via non-covalent interaction

Biomolecule-based hydrogels have potential use in a wide range of applications such as controlled drug release, tissue engineering, and biofabrication. Herein, driven by specific interactions between ds-DNA (double-stranded DNA) and Zn2+ based metal-complexes, we report that the use of DNA as cross-linkers can enhance interactions between self-assembling Zn2+ complexes containing terpyridine and sugar groups in the generation of bioinspired hydrogels from solutions or suspensions. The gelation process is fast and straightforward without tedious steps and happens at room temperature. Such a hydrogelation process of different Zn2+ complexes endows the visualized and selective DNA analogue discrimination. Several experiments suggest that the strong intercalation binding of Zn2+ complexes with ds-DNA results in the unzipping of ds-DNA into ss-DNA (single-stranded DNA), which further behave as linkers to enhance the intermolecular interactions of self-assembling Zn2+ complex molecules via coordination interactions. This work demonstrates an efficient and universal strategy to prepare hydrogels based on biomolecular recognition. Moreover, the DNA responsive behaviors of Zn2+ complexes are further compared with that of solutions and cells.

Infinite coordination polymer networks: metallogelation of aminopyridine conjugates and in situ silver nanoparticle formation

Herein we report silver(i) directed infinite coordination polymer network (ICPN) induced self-assembly of low molecular weight organic ligands leading to metallogelation. Structurally simple ligands are derived from 3-aminopyridine and 4-aminopyridine conjugates which are composed of either pyridine or 2,2'-bipyridine cores. The cation specific gelation was found to be independent of the counter anion, leading to highly entangled fibrillar networks facilitating the immobilization of solvent molecules. Rheological studies revealed that the elastic storage modulus (G') of a given gelator molecule is counter anion dependent. The metallogels derived from ligands containing a bipyridine core displayed higher G' values than those with a pyridine core. Furthermore, using single crystal X-ray diffraction studies and ¹H-¹⁵N two-dimensional (2D) correlation NMR spectroscopy, we show that the tetracoordination of silver ions enables simultaneous coordination polymerization and metallosupramolecular cross-linking. The resulting metallogels show spontaneous, in situ nanoparticle (d < 2-3 nm) formation without any additional reducing agents. The silver nanoparticle formation was followed using spectroscopic studies, and the self-assembled fibrillar networks were imaged using transmission electron microscopy (TEM) imaging.

Heterometallic Coordination Polymer Gels Supported by 2,4,6-Tris(pyrazol-1-yl)-1,3,5-triazine

Complexes of type [M(tpt)₂]X₂ (M²⁺ = Fe²⁺, Co²⁺, Ni²⁺; tpt = 2,4,6-tri{pyrazol-1-yl}-1,3,5-triazine; X^- = BF₄ ^- or ClO₄ ^-) crystallize in a cubic lattice, with the metal ion and ligand conformation showing unusual symmetry-imposed disorder. Addition of 1 equiv AgX to the corresponding preformed [M(tpt)₂]X₂ salt in concentrated MeNO₂ solution affords thixotropic gels. Gelation was not observed in analogous reactions using [Mn(tpt)₂][ClO₄]₂, or from reactions in other, more donating solvents. Scanning electron microscopy (SEM) images from dilute solutions of the reagents confirmed the fibrous microstructure of the gels and their homogeneous elemental composition. However, energy-dispersive X-ray data show a reduced Fe/Ag ratio compared to the Co/Ag and Ni/Ag gels, where a 1:1 ratio of metals is evident. More concentrated gels decomposed to silver nanoparticles during SEM sample preparation. Mass spectrometry and ¹H NMR indicate that silver induces partial ligand displacement reactions in [Fe(tpt)₂]²⁺ and [Co(tpt)₂]²⁺, but not in [Ni(tpt)₂]²⁺. Hence, the strength of the gels, which follows the order M = Mn (no gel) < Fe < Co < Ni, correlates with the stability of octahedral [M(tpt)₂]²⁺ under gelation conditions. Iron(II) complexes of the related ligands 2,4,6-tri{pyrazol-1-yl}pyridine (tpp) and 2,4,6-tri{pyrazol-1-yl}pyrimidine (tpym) did not undergo gelation with silver salts under the above conditions. The unique properties of tpt as a gelator in this work may reflect the crystallographically observed ability of metal-coordinated tpt to chelate to exogenous silver ions, through its pendant pyrazolyl group and triazinyl N donors. In contrast, the pendant azolyl substituents in silver complexes of the nongelators tpp and tpym only bind exogenous silver in monodentate fashion.

Two-electron redox-active tricyano iron(ii) complex with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine as a building block for coordination polymers

A new tricyano iron(ii) building unit, [{K(H2O)4}{FeII(CN)3(L)}]·3H2O (1), was synthesized by the reaction of Moor's salts with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (L) as a capping ligand. X-ray structural analysis reveals that the mononuclear iron(ii) tricyano complex consists of one ligand and three cyanide groups, with K+ ions coordinated between neighboring units to form a one-dimensional chain network structure. 1 shows two reversible redox waves at +0.713 and -0.849 V vs. SCE, which are assigned as Fe(ii)/Fe(iii) and L/L˙- processes, respectively. One-dimensional 4,2-ribbon chain type coordination polymers, [MII(H2O)2{FeII(CN)3(L)}2]·6H2O (M = Fe (2) and Mn (3)), were synthesized by using 1 as a building unit. Cryomagnetic studies reveals that 2 and 3 show paramagnetic behaviour of S = 2 and 5/2, respectively. On the other hand, reaction of 1 and Gd(NO3)3·6H2O forms another one-dimensional chain, [GdIII(NO3)2(H2O)3{FeII(CN)3(L)}]·0.5H2O·2CH3OH (4), showing S = 7/2 paramagnetic behaviour.

A supramolecular Cd(ii)-metallogel: an efficient semiconductive electronic device

A supramolecular Cd(ii)-metallogel with oxalic acid in DMF medium has been achieved, and the semi-conductive characteristics such as the Schottky barrier diode nature of the metallogel were explored.