Zinc Center Research Articles

Synthesis, Crystal Structures, Antimicrobial Activity, and Acute Toxicity Evaluation of Chiral Zn(II) Schiff Base Complexes

Four mononuclear bioefficient zinc coordination complexes [Zn(NN)3](ClO4)2 (A–D) involving chiral bidentate Schiff base ligands have been synthesized and characterized by IR, 1H, and 13C NMR spectroscopy and mass spectrometry. X-ray crystal structures of three of the zinc complexes revealed that the zinc metal ion is hexacoordinated, exhibiting a distorted octahedral geometry where both the nitrogen atoms (NN = pyridyl and imine) of imines are coordinated to the central zinc ion. The isolated zinc complexes were evaluated for their antimicrobial activity in vitro against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, displaying varying levels of growth inhibition. An acute toxicity test conducted using Artemia salina and Swiss albino mice showed that the zinc complexes A–D were non-toxic towards A. salina at concentrations below 414, 564, 350, and 385 µM, respectively, and did not affect liver biochemical parameters, although pyknosis was induced in hepatocytes of the treated mice.

Unveiling the mechanism of reverse saturable absorption in zinc tetrapyridyl porphyrins

Reverse saturable absorption (RSA) is one of the important mechanism for a molecule showing optical-limiting property. The experiment found that zinc tetrapyridyl porphyrins (ZnTPyP) exhibit distinct RSA characteristics at both 470 nm and 532 nm wavelengths. To understand the origin of the RSA in ZnTPyP, a theoretical analysis based on the linear-response time-dependent density functional theory(LR-TDDFT) for the ground state absorption (GSA) and the pseudo-wavefunction formulation of LR-TDDFT(PWF-TDDFT) for excited states absorption (ESA) were conducted. Experimentally observed RSA in ZnTPyP are well predicted. It is shown that the transitions of S1→S13,14,15,18 are the origin of the observed RSA feature in ZnTPyP. We found that these excited states transitions exhibit intramolecular charge transfer character and the pyridyl groups play an important role in the charge transfer process. It is also noticed that the pyridyl groups results in a red shift for both the GSA and ESA of porphyrin. In addition, the central zinc atom causes the energy gap between the positions with prominent absorption in GSA and ESA increased. These observations indicate that pyridyl groups and central zinc atom play an important role in tuning the spectral window and strength of RSA in the porphyrin complexes. These observations provide guidance for designing novel optical-limiting materials based on the porphyrin derivatives.

The efflux system CdfX exports zinc that cannot be transported by ZntA in Cupriavidus metallidurans.

Cupriavidus metallidurans is able to survive exposure to high concentrations of transition metals, but is also able to grow under metal starvation conditions. A prerequisite of cellular zinc homeostasis is a flow equilibrium combining zinc uptake and efflux processes. The mutant strain ∆e4 of the parental plasmid-free strain AE104 with a deletion of all four chromosomally encoded genes of previously known efflux systems ZntA, CadA, DmeF, and FieF was still able to efflux zinc in a pulse-chase experiment, indicating the existence of a fifth efflux system. The gene cdfX, encoding a protein of the cation diffusion facilitator (CDF) family, is located in proximity to the cadA gene, encoding a P-type ATPase. Deletion of cdfX in the ∆e4 mutant resulted in a further decrease in zinc resistance. Pulse-chase experiments with radioactive 65Zn(II) and stable-isotope-enriched 67Zn(II) provided evidence that CdfX was responsible for the residual zinc efflux activity of the mutant strain ∆e4. Reporter gene fusions with cdfX-lacZ indicated that the MerR-type regulator ZntR, the main regulator of zntA expression, was responsible for zinc- and cadmium-dependent upregulation of cdfX expression, especially in mutant cells lacking one or both of the previously characterized efflux systems, ZntA and CadA. Expression of zntR also proved to be controlled by ZntR itself as well as by zinc and cadmium availability. These data indicate that the cdfX-cadA region provides C. metallidurans with a backup system for the zinc-cadmium-exporting P-type ATPase ZntA, with CdfX exporting zinc and CadA cadmium.IMPORTANCEBacteria have evolved the ability to supply the important trace element zinc to zinc-dependent proteins, despite external zinc concentrations varying over a wide range. Zinc homeostasis can be understood as adaptive layering of homeostatic systems, allowing coverage from extreme starvation to extreme resistance. Central to zinc homeostasis is a flow equilibrium of zinc comprising uptake and efflux reactions, which adjusts the cytoplasmic zinc content. This report describes what happens when an imbalance in zinc and cadmium concentrations impairs the central inner-membrane zinc efflux system for zinc by competitive inhibition for this exporter. The problem is solved by activation of Cd-exporting CadA or Zn-exporting CdfX as additional efflux systems.

Rational Assembly of Three-component Coordination Polymers as Heterogeneous Catalysts for CO2 Cycloaddition and Cyanosilylation Reactions.

Four new coordination polymers based on 5-(((1H-imidazol-2-yl)methyl)amino) isophthalic acid (H3L) and auxiliary ligands (1,10-phenanthroline, 2,2'-bipyridine, and 4,4'-bipyridine), namely, {[Zn(HL)(phen)(H2O)]·2H2O}n (CP 1), {[Ni(HL)(phen)(H2O)]}n (CP 2), {[Ni(HL)(2,2'-bpy)(H2O)]·2H2O}n (CP 3) and {[Cd(HL)(4,4'-bpy)0.5(H2O)]·2H2O}n (CP 4) were rationally assembled. Furthermore, these four CPs were screened as heterogeneous catalysts for CO2 cycloaddition and cyanosilylation reactions under mild conditions. The catalytic experiments showed that CP 1 had the better catalytic performance, excellent substrate tolerance and recyclability for the above two reactions. It is speculated that the excellent activity of CP 1 may be due to the open Lewis base site and the Lewis acidic characteristics of the zinc (II) center. After five cycles, the catalytic activities of CP 1 did not significantly decrease, and the structures remained unchanged. Therefore, the CP 1 was considered efficient and stable heterogeneous catalysts for above the two reactions.

Synthesis, characterization, and crystal structure of hexa-kis-(1-methyl-1H-imidazole-κN 3)zinc(II) dinitrate.

The synthesis of the title compound, [Zn(C4H6N2)6](NO3)2, is described. This complex consists of a central zinc metal ion surrounded by six 1-methyl-imidazole ligands, charge balanced by two nitrate anions. The complex crystallizes in the space group P. In the crystal, the nitrate ions are situated within the cavities created by the [Zn(N-Melm)6]2+ cations, serving as counter-ions. The three oxygen atoms of the nitrate ion engage in weak C-H⋯O inter-actions. In addition to single-crystal X-ray diffraction analysis, the complex was characterized using elemental analysis, 1H NMR, 13C NMR, and FTIR spectroscopy.

Virtual screening reveals fluorescent probes for detecting Pan-Zinc center activity in serum MMPs: A potential biomarker for early tumor screening

Early tumor screening is pivotal for enhancing tumor treatment efficacy and patient survival rates, yet identifying reliable biomarkers for early detection remains a challenge. Previous studies have explored different isoforms of matrix metalloproteinases (MMPs) in serum for their predictive value in tumor, but their results have been inconsistent. Herein, we introduce a novel fluorescent probe, C9 (N-oxide-8-hydroxyquinoline-5-sulfonic acid), designed to specifically label the pan zinc center activity of MMPs (PZCA-MMPs), which in a sense represents the overall MMPs activity in serum. The rational design of fluorescent probe C9 is based on its ability to bind the zinc ions in the structure of MMPs, facilitated by the oxides on hydroxyl (–OH) and nitro oxide (N→O) groups present in C9, as supported by theoretical calculations such as Gaussian and Schrödinger. Experimental validation confirmed its efficacy for detecting PZCA-MMPs in vitro and for fluorescence imaging of MMPs’ zinc ions in cellular contexts, validated through absolute integrated fluorescence intensity measurements at 510 nm. We also demonstrated through in vitro fluorescent analysis that neither metal ions nor abundant serum proteins such as albumin (BSA) and other metalloproteins interfere with the signal response of C9. Notably, in comparative analysis of serum samples from healthy controls and breast tumor patients, PZCA-MMPs showed a highly discriminatory area under the ROC curve (AUC) of 0.9377, surpassing established tumor biomarkers such as CA125, CA15-3, CA19-9, and CA72-4. In particular, for tumor patients, PZCA-MMPs can effectively distinguish between metastatic and non-metastatic patients (*P<0.05). Therefore, this provides a potential alternative biomarker for tumor screening. Future studies aim to further elucidate the clinical utility of PZCA-MMPs using a broader spectrum of clinical samples.

Coordination Chemistry of Calix[3]Pyrrole-Related Macrocycles

Calix[3]pyrrole is a ring-contracted porphyrinogen-like macrocycle in which three pyrrole units are linked by three sp3-carbon atoms at the a-positions. While synthetic routes to calix[3]pyrrole and its furan and thiophene derivatives have been established using oligoketone precursors,[1–3] their coordination chemistry remains fully unexplored. Here, the author reports the direct macrocyclization synthesis and metal complexation properties of novel thiazole-containing calix[3]pyrrole analogues that exhibit better metal chelation than that of calix[3]pyrrole.Treatment of calix[3]pyrrole (1) with n-butyl lithium (4 eq.) resulted in the deprotonation of all the NH protons to generate a tridentate trianionic ligand. Successive reaction with BBr3 furnished a boron(III)-complex 2 in 25% isolated yield. However, attempts to synthesize stable complexes with other metal ions were unsuccessful. The obtained boron complex 2 were unusually stable towards acids; even in pure trifluoroacetic acid (TFA) or methanesulfonic acid, no deboronation was observed, instead, protonation at a pyrrole carbon atom was detected by NMR spectroscopy.In order to generate isolable metal complexes with calix[3]pyrrole-related macrocycles, we have designed calix[1]pyrrole[2]thiazole (4). Calix[1]furan[2]thiazole (3), a precursor of 4, was synthesized by direct macrocyclization between bis(a-bromoketone) and 2,2-dimethylpropanebis(thioamide) in 60% yield. While calix[3]pyrrole (1)undergoes a strain-induced ring expansion reaction to give calix[6]pyrrole under acidic conditions, less strained 3 was stable in TFA, thus its furan moiety was hydrolyzed to a diketone moiety. Further Paal–Knorr pyrrole formation reaction led to the formation of 4 in 78% yield.When macrocycle 4 was mixed with Et2Zn, monoethyl zinc complex 5 was formed in 72% yield. Single crystal X-ray analysis revealed that 4 adopted a C s-symmetric cone conformation to behave as a monoanionic tridentate ligand. Due to the steric protection of the ethyl zinc center by meso-methyl groups, organozinc complex 5 was stable in the presence of excess water or alcohol at room temperature.Complexation of 4 with Pd(MeCN)4(BF4)2 afforded cationic palladium complex 6 in which macrocycle 4 adopted a partial cone conformation to chelate a Pd2+ ion as a neutral bidentate ligand. Similar complexation behavior was also observed with AgBF4, demonstrating conformational flexibility of macrocycle 4 upon metal complexation. Furthermore, coordination-driven self-assembly was confirmed for Ag+ complex of 4.In this presentation, the detailed synthesis and electronic properties of the metal complexes of calix[3]pyrrole-related macrocycles will be discussed.

(Digital Presentation) In-Situ Growth of CNT and Macroporous ZIF on Bacterial Cellulose for High Frequency Electrochemical Capacitor

High frequency electrochemical capacitors (HF-ECs) represent a class of devices characterized by their high capacitive density and operational capability within the hundreds or kilohertz range. As electronic devices continue to undergo downsizing trends, HF-ECs emerge as promising alternatives to bulky aluminum electrolytic capacitors (AECs), which are constrained by their limited working frequency of approximately 1 Hz and slow charge-discharge rates. The designing of electrodes of HF-ECs combines large surface area for capacitive density along with open porous network to facilitate rapid ion transport. In this study, we synthesized nickel coordinated ZIF-8 (Zeolitic Imidazole Framework-8) cages on bacterial cellulose (BC). The samples underwent rapid carbonization in the presence of dicyandiamide at ~950˚C for 20 minutes, during which the zinc centers inside the MOF cages evaporated forming macroporous structures, while the nickel particles gave rise to carbon nanotube (CNT) growth through tip growth mechanism. The uniform coverage of BC with macroporous ZIF cages reduces the microporous effect, while the CNT growth also imparts higher electronic conductivity via graphitic nitrogen groups. The HF-ECs made with these electrodes and 6M KOH aqueous electrolyte gave a capacitive density of ~3.4 mFcm-2 and a phase angle of -81.3˚. The electrodes were stacked in pairs of 2 and 3 to achieve higher capacitance of 6.3 mFcm-2 and 8.9 mFcm-2 respectively. The HF-ECs were also assembled with 1 M TEABF4 in acetonitrile to show higher working voltage of these electrodes. The device maintained a capacitance just above 3 mFcm-2 and a phase angle over -80˚. The cells show an excellent working capability at higher discharge rates of 100 mAcm-2, where they retained ~70% of the initial capacitance. Figure 1

N,N’-bis(3-dithiocarbamatopropyl) piperazine bridged metallomacrocyclic complexes of Ni(II), Cu(II) and Zn(II): Synthesis, characterization, photophysical, in-silico study and their potential utility in heavy metal ion sensing

Two secondary diamines viz. N,N’-bis{3-(p-methoxybenzylamino)propyl}piperazine (H2L1) and N,N’-bis{3-(p-chlorobenzylamino)propyl}piperazine (H2L2) holding N,N’-bispropylpiperazine linkers have been prepared and subsequently used to derive a new series of N,N’-bis(3-dithiocarbamatopropyl) piperazine bridged metallomacrocyclic complexes [M(II)2-µ2-bis-{(κ2S,S-S2CN(R)C3H6)2piperazine}] wherein R = p-methoxybenzyl, M = Ni(II) 1, Cu(II) 2, Zn(II) 3; R = p-chlorobenzyl, M = Ni(II) 4, Cu(II) 5, Zn(II) 6. The formation and purity of all the metallomacrocyclic dithiocarbamate complexes were verified by microanalysis and standard methods such as HRMS, NMR, IR and UV–Visible absorption spectroscopy and corroborated by density functional theory calculations. The experimental (magnetic susceptibility and UV–Visible) and theoretical calculations suggest a square planar/distorted square planar environment around nickel(II)/copper(II) and tetrahedral/distorted tetrahedral environment around zinc(II) centres in 1–6. Thermogravimetric study was carried out on 1–6 to study their thermal stability and degradation behaviour. Notably, TG curves of compounds 2, 3 and 5 gave a stable residual mass corresponding to corresponding metal sulphides (MS). Notably, the calculated HOMO-LUMO gaps (1.19–1.33 eV) for Cu(II)-dithiocarbamate 2 and 5 indicates their semiconducting nature. The potentials of these metallomacrocycles as a molecular probe for optical sensing of environmentally hazardous heavy metal ions ca Pb(II), Cd(II) and Hg(II) were further examined by using UV–Visible and fluorescence spectroscopies.

Blue‐Emissive Fluorescent Zinc(II) Complexes with Bis(imidazo[1,5‐a]pyridine)methane Ligands

Three bis(imidazo[1,5‐a]pyridine)methane derivatives (bis(1‐methylimidazo[1,5‐a]pyridin‐3‐yl)methane, LH; 3,3'‐(ethane‐1,1‐diyl)bis(1‐methylimidazo[1,5‐a]pyridine) LMe; 3,3'‐(2‐phenylethane‐1,1‐diyl)bis(1‐methylimidazo[1,5‐a]pyridine), LBz) have been synthesized, and fully characterized in solution (1H and 13C NMR spectra) and in the solid state (X‐ray). In particular, LH has been prepared in high yield (75%) under very mild conditions (water, 60°C), offering an alternative route to those reported in the literature. LMe and LBz have been obtained from LH by functionalization of the methylene bridge. The bis(imidazo[1,5‐a]pyridine)methane compounds have been coordinated to a zinc(II) center, leading to tetrahedral complexes of general formula [Zn(LR)2](ClO4)2 (R = H, Me, Bz), which showed a bright fluorescent emission with (x,y) color coordinates very close to standard blue. TD‐DFT have been employed to describe the Frontier Molecular Orbitals (FMOs) participating in electronic transitions, highlighting the main transition as 1(π‐π*) transition in the bis(imidazo[1,5‐a]pyridine)methane and a mixed intra‐ligand (1ILT) and ligand‐to‐ligand (1LLT) transition in the complexes.

Spotlight on Zinc: Exploring the Visible Light Responsiveness of Zinc Complexes.

Group 12 element zinc(II)-based d10 complexes have long been known for their inherent colorlessness, which has limited their applications in visible light-driven photophysical and photochemical applications, despite the attractiveness of inexpensive and low-toxicity zinc metal. Based on precedents with nickel(0) and copper(I) complexes, which also adopt the d10 electronic configuration, achieving a visible light response from zinc(II) complexes seems feasible; however, investigations and proactive design strategies specifically tailored to zinc remain lacking. In this context, the present invited concept paper highlights zinc's potential for visible light responsiveness and evaluates how molecular designs can achieve this capability. After delineating the differences between zinc and other d10 metal centers, we review recent developments in zinc complexes that exhibit visible light absorption and compare these complexes with previously reported colorless complexes to identify key distinctions. This study provides critical insights into the molecular design guidelines that are pivotal for harnessing the emerging potential of zinc for visible light responses.

Two-point connected complex of zinc aminoporphyrin with histidine protected at α-amino and imidazolyl-π nitrogen atoms

Abstract Zinc porphyrins possessing an (N,N-dialkylamino)methyl group at the peripheral position were prepared from β-octaethylporphyrin. The synthetic zinc aminoporphyrins were complexed with an Nα,Nim(τ)-protected histidine through the coordination of the histidyl imidazolyl-τ nitrogen atom with the central zinc atom and the concomitant hydrogen bonding of the histidyl carboxy group with the peripheral amino group. The 1:1 complexation in the chloroform was dependent on the size of the alkyl groups on the peripheral aminomethyl nitrogen atom. The diethyl substitute complexed more strongly than the dimethyl and dipropyl counterparts. The complexation of zinc (diethylamino)methyl-porphyrin with an Nα,Nim(π)-protected histidine was 260-fold stronger than that with the above Nα,Nim(τ)-protected histidine to exhibit the association constant of 2.6 × 106 M−1. The significant enhancement was ascribable to the less sterically demanding and more coordinating Nim(τ)-atom compared with the Nim(π)-atom. The achiral zinc aminoporphyrin was complexed with the chiral Nα,Nim(π)-protected histidine to give a circular dichroism active species in a visible Soret region.

Unexpectedly High Propylene/Propane Separation Performance of Asymmetric Mixed-Matrix Membranes through Additive-Assisted In Situ ZIF-8 Filler Formation: Experimental and Computational Studies.

Zeolitic-imidazolate framework-8 (ZIF-8), composed of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, has garnered extensive attention as a selective filler for propylene-selective mixed-matrix membranes (MMMs). Recently, we reported an innovative and scalable MMM fabrication approach, termed "phase-inversion in sync with in situ MOF formation" (PIMOF), aimed at addressing the prevailing challenges in MMM processing. In this study, we intend to investigate the effect of additives, specifically sodium formate and 1,4-butanediol, on the modification of ZIF-8 filler formation within the polymer matrix in order to further improve the separation performance of the asymmetric MMMs prepared by the PIMOF. Remarkably, MMMs prepared with sodium formate as an additive in the coagulation bath exhibited an unprecedented C3H6/C3H8 separation factor of 222.5 ± 1.8 with a C3H6 permeance of 10.1 ± 0.3 GPU, surpassing that of MMMs prepared without additives (a C3 separation factor of 57.7 ± 11.2 with a C3 permeance of 22.5 ± 4.5 GPU). Our computational work complements the experimental investigation by studying the effect of ZIF-8 nanoparticle size on the specific surface interaction energy and apertures of ZIF-8. Calculations indicate that by having smaller ZIF-8 nanoparticles, stronger interactions are present with the polymer affecting the aperture of ZIF-8 nanoparticles. This reduction in aperture size is expected to improve selectivity toward propylene by reducing the permeability of propylene. These results represent a significant advancement, surpassing the performance of all previously reported propylene-selective MMMs and most high-quality polycrystalline ZIF-8 membranes. The notably enhanced separation performance primarily arises from the formation of exceedingly small ZIF-8-like particles with an amorphous or poorly crystalline structure, corroborated by our computational work.

The unanti-cipated oxidation of a tertiary amine in a tetra-cyclic glyoxal-cyclam condensate yielding zinc(II) coordinated to a sterically hindered amine oxide.

The complex, tri-chlorido-(1,4,11-tri-aza-8-azonia-tetra-cyclo-[6.6.2.04,16.011,15]hexa-decane 1-oxide-κO)zinc(II) monohydrate, [ZnCl3(C12H23N4O)]·H2O, (I), has monoclinic symmetry (space group P21/n) at 120 K. The zinc(II) center adopts a slightly distorted tetra-hedral coordination geometry and is coordinated by three chlorine atoms and the oxygen atom of the oxidized tertiary amine of the tetra-cycle. The amine nitro-gen atom, inside the ligand cleft, is protonated and forms a hydrogen bond to the oxygen of the amine oxide. Additional hydrogen-bonding inter-actions involve the protonated amine, the water solvate oxygen atom, and one of the chloro ligands.

Crown-ether threaded covalent organic polyrotaxane framework (COPF) towards synergistic crown/Zn2+/photothermal/photodynamic antibacterial and infected wound healing therapy

Controllable preparation of materials with new structure has always been the top priority of polymer materials science research. Here, the supramolecular binding strategy is adopted to develop covalent organic frameworks (COFs) with novel structures and functions. Based on this, a two-dimensional crown-ether ring threaded covalent organic framework (COF), denoted as Crown-COPF with intrinsic photothermal (PTT) and photodynamic (PDT) therapeutic capacity, was facilely developed using crown-ether threaded rotaxane and porphyrin as building blocks. Crown-COPF with discrete mechanically interlocked blocks in the open pore could be used as a molecular machine, in which crown-ether served as the wheel sliding along the axle under the laser stimulation. As a result, Crown-COPF combining with the bactericidal power of crown ether displayed a significant photothermal and photodynamic antibacterial activity towards both the Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus), far exceeding the traditional Crown-free COF. Noteworthily, the bactericidal performance could be further enhanced via impregnation of Zn2+ ions (Crown-COPF-Zn) flexible coordinated with the multiple coordination sites (crown-ether, bipyridine, and porphyrin), which not only endow the positive charge with the skeleton, enhancing its ability to bind to the bacterial membrane, but also introduce the bactericidal ability of zinc ions. Notably, in vivo experiments on mice with back infections indicates Crown-COPF-Zn with self-adaptive multinuclear zinc center, could effectively promote the repairing of wounds. This study paves a new avenue for the effectively preparation of porous polymers with brand new structure, which provides opportunities for COF and mechanically interlocked polymers (MIPs) research and applications.

Mammalian Cell Cytotoxicity, Antibacterial Activity and the Properties of Methylenebis(Hydroxybenzoic Acid) and Its Related Zinc(II) Complex

Formaldehyde, sulfuric acid and salicylic acid were combined to create a 3,3′-methylenebis(2-hydroxybenzoic acid) (MHB) ligand, which was subsequently permitted to bind with zinc(II) ions. The ligand and its zinc(II) complex (Zn–MHB) have been described by a combination of elemental analyses, spectral analyses (UV–Vis, IR, MS and NMR), XRD, TEM, as well as TGA measurement. The ligand has been suggested to coordinate to the zinc center in a tetradentate manner forming the binuclear tetrahedral complex. An X-ray analysis indicated a considerable difference between MHB (crystalline) and Zn–MHB (amorphous). The UV–Vis spectra were used to determine the optical properties such as bandgap, refractive index, optical conductivity and penetration depth. The possibility of employing the samples for optoelectronic applications was indicated from the band gap values which underlie the range of semiconductors. TEM revealed the spherical shapes and mutation of ligand particles into the nano-scale by complexation. The antimicrobial potential of the MHB towards Gram-positive and Gram-negative bacterial growths has been investigated. The results suggested that it would be possible to employ MHB to prevent bacterial development, particularly that of salmonella typhimurium. The cytotoxicity of the MHB was assessed against two types of mammalian cells: VERO (the kidney of an African green monkey) and HFB4 (human skin melanocytes). Lower sensitivity was observed in VERO cells.

A solution-processable benzothiazole-substituted formazanate zinc(II) complex designed for a robust resistive memory device.

A novel mononuclear bis(formazanate)zinc complex (1) based on a redox-active 1-(benzothiazol-2-yl)-5-(2-benzoyl-4-chlorophenyl)-3-phenyl formazan ligand has been synthesized and characterized. Complex 1 was prepared by reacting one equivalent of Zn(OCOCH3)·2H2O with two equivalents of the corresponding formazan derivative. X-ray crystallography was employed to ascertain the solid-state structure of compound 1, and the analysis revealed a distorted octahedral geometry for the complex where the symmetrical ligands exhibit a preference for coordinating with the zinc center in the 'open' form, generating five-membered chelate rings. Moreover, cyclic voltammetry analysis reveals that complex 1 exhibits the capacity for electrochemical reduction as well as oxidation, resulting in the formation of radical anionic (L2Zn-) and dianionic (L2Zn2-) states as well as the oxidation state of 1. Additionally, the developed solution-processable complex 1 was employed as the fundamental building material for resistive switching memory applications. The [FTO/ZnIIL2(1)]/Ag RRAM device demonstrates exceptional resistive memory switching properties, with a substantial ION/IOFF ratio (103), low operational VSET and VRESET (0.9 V and -0.75 V) voltages, excellent endurance stability (100 cycles), and decent retention time (more than 2000 seconds). The findings presented in this study underscore the importance of redox-active formazanate metal complexes for creating promising memory storage devices.

Polymorphism and flexibility of six-porphyrin nanorings in the solid state.

Butadiyne-linked porphyrin nanorings are fascinating nanometer-sized platforms for exploring electronic delocalization and aromaticity, and they mimic ultra-fast photosynthetic energy-transfer phenomena in plants and purple bacteria. However, little is known about how they interact in the solid state. Here, we compare the crystal structures of several pseudopolymorphs of a six-porphyrin nanoring template complex, and report the structure of the free-base nanoring co-crystallized with C60. The structures differ not only in the molecular packing; they also feature different molecular conformations. The template is slightly too small for the cavity of the nanoring, and this size mismatch can be accommodated by two types of distortion: either the zinc atoms are pulled away from the planes of the porphyrins, or the nanorings contract by adopting a ruffled conformation, with butadiyne links alternatingly above and below the plane of the six zinc centers. The template-bound ring forms sheets and tubular stacks with interdigitated aryl groups. Upon demetallation, the nanoring becomes more flexible, adopting a highly elliptical conformation on co-crystallization with C60. The structure of this free-base nanoring features infinite solvent filled channels with a channel diameter of 13.5 Å. The high porosity of these materials points towards possible applications as porous light-harvesting frameworks.

The synthesis and structural properties of a chlorido-bis-{N-[(4-meth-oxy-phen-yl)imino]-pyrrolidine-1-carboxamide}-zinc(II) (aceto-nitrile)-trichlorido-zincate coordination complex.

The title complex, [ZnCl(C12H15N3O2)2][ZnCl3(CH3CN)], was synthesized and its structure was fully characterized through single-crystal X-ray diffraction analysis. The complex crystallizes in the ortho-rhom-bic system, space group Pbca (61), with a central zinc atom coordinating one chlorine atom and two pyrrolidinyl-4-meth-oxy-phenyl azoformamide ligands in a bidentate manner, utilizing both the nitro-gen and oxygen atoms in a 1,3-heterodiene (N=N-C=O) motif for coordinative bonding, yielding an overall positively (+1) charged complex. The complex is accompanied by a [(CH3CN)ZnCl3]- counter-ion. The crystal data show that the harder oxygen atoms in the heterodiene zinc chelate form bonding inter-actions with distances of 2.002 (3) and 2.012 (3) Å, while nitro-gen atoms are coordinated by the central zinc cation with bond lengths of 2.207 (3) and 2.211 (3) Å. To gain further insight into the inter-molecular inter-actions within the crystal, Hirshfeld surface analysis was performed, along with the calculation of two-dimensional fingerprint plots. This analysis revealed that H⋯H (39.9%), Cl⋯H/H⋯Cl (28.2%) and C⋯H/H⋯C (7.2%) inter-actions are dominant. This unique crystal structure sheds light on arrangement and bonding inter-actions with azo-formamide ligands, and their unique qualities over similar semicarbazone and azo-thio-formamide structures.

Antibacterial, antibiofilm, and antioxidant activities of two novel metal-organic frameworks (MOFs) based on 4,6-diamino-2-pyrimidinethiol with Zn and Co metal ions as coordination polymers.

In the present era, the increase in free radical species (FRs) and multidrug-resistant (MDR) bacteria represents a major worldwide concern for public health. Biofilm development and the overuse and misuse of antibiotics could lead to the adaptation of bacteria to antimicrobial agents. Consequently, finding novel multifunctional species with antibacterial, antioxidant, and antibiofilm properties has become crucial in the fight against challenging bacterial infections and chronic inflammatory conditions. Metal-organic frameworks (MOFs) with zinc and cobalt metal centers are widely utilized in biological and environmental remediation owing to their versatility. In this study, multifunctional Zn-MOFs and Co-MOFs were successfully synthesized with zinc and cobalt as metal centers and 4,6-diamino-2-pyrimidinethiol as an organic linker using a hydrothermal technique. Numerous characterization techniques were used to fully examine the MOF structure, functionality, chemical makeup, crystalline structure, surface appearance, thermal behavior, and magnetic characteristics; the techniques included XPS, PXRD, FTIR, FESEM, EDX, UV-visible, BET, BJH, TGA/DTG, DSC, and magnetic susceptibility measurement. The antioxidant, antibacterial, and antibiofilm activities of the MOFs were examined, and they demonstrated potent activity in each of these aspects. The proposed mechanisms of antibacterial activity suggest that bacterial cell death results from multiple toxic effects, including electrostatic interaction and lipid peroxidation, when MOFs are attached to bacteria, leading to the formation of reactive oxygen species (ROSs). Zn-MOFs exhibit high antibacterial and antibiofilm efficacy owing to their large surface-to-volume ratio and porous nature, while Co-MOFs exhibit high antioxidant capacity owing to their redox properties.