Imidazole Ligands Research Articles

MOF@ Nanofiber Separators for Lithium‐Ion Batteries

ABSTRACTThe separator plays a crucial role in determining the safety and performance of lithium‐ion batteries (LIBs) by acting as a mediator between the cathode and anode, preventing electrical contact, and providing channels for ionic transport. Most commercially available LIB separators are polyolefin microporous separators. However, the low melting points of polyolefin separators limit their thermal stability, leading to potential safety issues. Therefore, new alternatives are essential for developing high‐performance batteries. Nylon 6,6 is a promising candidate due to its high thermal stability, low cost, good mechanical strength, and high chemical stability. One effective method to further improve the performance of nylon 6,6 separators is to combine them with Metal–Organic Frameworks (MOFs), which offer a high surface area and tunable morphology. The high surface area and porous structure provided by MOFs can increase ion permeability and allow the electrolyte to move more efficiently, thus improving the battery's charge/discharge rates and enhancing its specific capacity. In this study, ZIF‐8, a small‐pore MOF composed of zinc ions coordinated with 2‐methyl imidazolate ligands, was coated onto nylon 6,6 nanofibers and used as a separator in lithium‐ion batteries. ZIF‐8@nylon 6,6 separators exhibited superior electrochemical properties, with a highly porous structure (76% porosity), high electrolyte uptake (340%), and high ionic conductivity (3.6 mS cm−1). Additionally, these separators showed stable cycling performance over 200 cycles and maintained a high specific capacity even at high C‐rates. The results demonstrate that MOF coating on nylon 6,6 separators is a promising approach for designing high‐performance lithium‐ion batteries.

Heteronuclear coordination polymers with imidazole ligand: Synthesis, characterization and alcohol oxidation activities

Two new heteronuclear Cd(II)/Pd(II) coordination polymers, [Cd2(µ-im)2(Him)4Pd(µ-CN)4]n (1) and [Cd(Him)2Pd(µ-CN)4]n (2) (Him: imidazole), have been synthesized under different conditions and characterized using elemental analysis, thermal analysis, FT-IR and Raman spectroscopy, single-crystal and powder X-ray diffraction techniques. In 1, the Cd(II) ions are bridged by imidazolate ligands to generate 1D chain structure. Neighbouring 1D chains were linked by [Pd(CN)4]2- ions to form 3D framework. In 2, the metal ions are bridged by cyanide ligands to generate 2D [Cd2Pd2(µ-CN)4]n network. Catalytic peroxidative oxidation activity of 1 and 2 was examined on the oxidation of benzyl alcohol using tertiary-butyl hydroperoxide (t-BuOOH) as the oxygen source. The compound 1 exhibited over 90 % product conversion at 80 °C in 24-hour reaction time. In addition, the catalyst exhibited high selectivity towards benzaldehyde and no over-oxidation product (benzoic acid) was detected.

7798 A Prospective Within-Patient Comparison of Molecular Imaging Ligands for Detection Of Surgically Curable Primary Aldosteronism (PA), and an Assessment of Accuracy in Cortisol Co-Secretors

Abstract Disclosure: E. Goodchild: None. X. Wu: None. R. Senanayake: None. J. MacFarlane: None. G. Argentesi: None. K. Laycock: None. C. Cabrera: None. S.M. O'Toole: None. J. Salsbury: None. D. Benu: None. Y. Lee: None. A. Chua: None. M. Mattson: None. P. Laila: None. N. Hilliard: None. M. Alison: None. D. Berney: None. K. Drew: None. C. Mein: None. E. Wozniak: None. J. Kearney: None. A. Sahdev: None. N. Bird: None. G. Smith: None. M. Hird: None. V. Warnes: None. D. Gillett: None. F. Aigbirhio: None. A. McIntosh: None. A. McConnachie: None. K. Cruickshank: None. H. Cheow: None. M. Gurnell: None. W. Drake: None. M.J. Brown: None. Introduction: Molecular imaging could reduce the need for invasive, scarcely-available adrenal sampling (AVS) to identify aldosterone-producing adenomas (APAs). Easily-distributable ligands for widespread use will be needed. Imidazole ligands lacking selectivity ex vivo for CYP11B1 and CYP11B2 are rendered selective in vivo by pre-treatment with dexamethasone. Aims To determine whether post-dexamethasone para-chloro-2-[[1]8F]fluoroethyletomidate PET-CT (CETO) (T ½ 110min), is interchangeable with previously validated [[1][1]C]-metomidate PET-CT (MTO) (T ½ 20min) for the diagnosis of APA. To identify whether a non-fully-suppressed cortisol after prolonged (72h) low-dose dexamethasone forewarns of an increased risk of a false-positive MTO result, in the MATCH study cohort.1Experimental design Prospective within-patient comparison of diagnostic interventions (n=31), with independent scoring of each as high, medium, low probability of unilateral PA, blind to scoring of the other scan or AVS. Prospective measurements of cortisol after prolonged low-dose dexamethasone suppression (PLDDF) and urinary hybrid steroids, with 6-month post-operative PASO biochemical outcomes and APA somatic genotyping when high probability (MTO or AVS) mandated surgery. Major results MTO and CETO agreed in 29/31, kappa=0.85 [95%CI 0.68,1.00]. Scatter was evenly distributed on either side of zero on Bland-Altman analysis (bias -0.04, [95% CI -0.12,0.04]. Of all 174 MATCH-study patients (n=174) PLDDF was available in 156, 32 had PLDDF >25nmol/L. Of these, MTO scored 16 as high probability of unilateral PA, in whom there was complete PASO biochemical success in 14 (88%), and absent in 2 (12%), indicating possible false-positives (AVS had failed in both). In patients with PLDDF </=25nmol/L, MTO identified unilateral disease in 22, 19 (86.3%) of whom had complete biochemical success at 6 months, 3 (13.6%) with partial or absent success. 22 patients had both an elevated PLDDF and urinary hybrid steroid profiles measured, of whom 4 had an elevated 18OH/F ratio. PLDDF in unilateral and not-unilateral MTO outcome were comparable (unpaired T test p= 0.92). A known somatic genotype mutation was found in 21 patients with PLDDF >25nmol/l. PLDDF was highest in KCNJ5 mutants (12/21, mean 55.3nmol/L), compared to ATP1A1 (3/21, mean 44nmol/L), CACNA1D (4/21, mean 31nmol/L), ATP2B3 (1/21, 36nmol/L) and GNAQ (1/21, 28nmol/L). All had complete biochemical success at 6 months post-op. Conclusion: CETO is interchangeable with MTO, which is non-inferior to AVS, in lateralising aldosterone excess in PA patients. False-positives rarely occurred by MTO, and autonomous cortisol secretion did not increase the chance of a false-positive MTO result, compared to patients without, in this cohort. Reference: (1) Wu X et al. Nature Medicine. 2023;29:190-202. Presentation: 6/3/2024

Construction of 2D zinc(II) MOFs with tricarboxylate and N-donor mixed ligands for multiresponsive luminescence sensors and CO2 adsorption.

The solvothermal reactions of ZnCl2·6H2O, benzene-1,3,5-tribenzoic acid (H3btb), and N-heterocyclic ancillary imidazole (Im) or aminopyrimidine (a mp) ligands led to the creation of two-dimensional (2D) zinc(II) based metal-organic frameworks (MOFs), (Me2NH2)2[Zn2(btb)2(Im)2]·2DMF·3MeOH (1) and (Me2NH2)2[Zn2(btb)2(amp)]·H2O·2DMF·MeOH (2). The btb3- ligands in 1 and 2 form an anionic 2D layered structure with a (63) honeycomb (hcb) topology by linking to Zn(II) centres through their carboxylate groups. The incorporation of N-heterocyclic auxiliary ligands Im and amp into the hcb nets resulted in the formation of a 2D hydrogen-bonded and covalently pillared bilayer structure featuring two-fold interpenetrating networks. Each of these networks consists of small channels that are occupied by Me2NH2 cations and solvent molecules. Both 1 and 2 emit blue luminescence emissions in the solid state at room temperature and exhibit a great selectivity and sensitivity for the detection of acetone and multiple heavy metal ions including Hg2+, Cu2+, Fe2+, Pb2+, Cr3+, and Fe3+ ions. At 1 bar, activated 1 and 2 demonstrate moderate capacities for adsorbing CO2 at room temperature, with a preference for CO2 over N2. Notably, at higher pressures (up to 20 bar), their activated samples 1 and 2 show a temperature-dependent enhancement of CO2 uptake while retaining good stability.

Synthesis of some metal ion complexes of new imidazole derivative, characterization, and biological activity

Imidazole complexes with high biological activity for some metal complexes prepared by a new imidazole ligand from the reaction of a 1,3-oxazole derivative with hydroxylamine and utilizing this ligand in the preparation of some metal ion complexes. Many of the techniques available for all prepared compounds, such as elemental analysis (CHNS), (FT-IR), (UV-Vis) spectra, and 1H-NMR spectra, will be used in the diagnosis of these complexes, and the forms of the complexes will be deduced from the results obtained. The outcomes demonstrated that the octahedral geometries of all the produced complexes, except for the copper and palladium complexes, which were square planer shapes. The antimicrobial activity of both the ligand and its metal ionic complexes against various microbes was evaluated. KEY WORDS: Imidazole, Oxazole, Spectral data, Bioactivity Bull. Chem. Soc. Ethiop. 2024, 38(6), 1681-1690. DOI: https://dx.doi.org/10.4314/bcse.v38i6.14

A structural and functional model for alkene dioxygenases

In this article, we report sterically-controlled iron sites based on non-chelating bulky imidazole ligands. Adding 6 equiv. of 1,2-dimethylimidazole (1,2-Me2Im) to Fe(OTf)2⋅2CH3CN affords the first example of a 5-coordinate imidazole‑iron complex ([Fe(1,2-Me2Im)5](OTf)2, 1). The structure is distorted square pyramidal (τ5 = 0.41). When an iPr group is substituted for the methyl group at the 2-position on the imidazole (2-iPr-1-MeIm), the 14-electron complex ([Fe(2-iPr-1-MeIm)4](OTf)2, 2) is obtained. This complex exhibits slightly distorted tetrahedral geometry (τ'4 = 0.93) with four N-donors and serves as a 4-His iron structural model complex for carotenoid cleavage dioxygenases (CCD). The electronic structure of 1 and 2 were characterized by Mössbauer spectroscopy. Reactions of 1 and 2 with model olefin substrates (1-R-4-(1-methoxyprop-1-en-2-yl)benzene; R = Me or Br) in the presence of oxygen result in olefin cleavage yielding ketone and aldehyde products, although 2 yields more products than 1. Support for a proposed reaction mechanism for 2 is offered from Density Functional Theory (DFT) calculations.

Decoding the Biomimetic Mineralization of Metal-Organic Frameworks in Water.

This study unveils the "green" metal-organic framework (MOF) structuring mechanism by decoding proton transfer in water during ZIF-8 synthesis. Combining in situ small- to wide-angle X-ray scattering, multiscale simulations, and quantum calculations, we reveal that the ZIF-8 early-stage nucleation and crystallization process in aqueous solution unfolds in three distinct stages. In stage I, imidazole ligands replace water in zinc-water cages, triggering an "acidity flip" that promotes proton transfer. This leads to the assembly of structures from single zinc ions to 3D amorphous cluster nuclei. In stage II, amorphous nuclei undergo a critical transformation, evolving into crystalline nuclei and subsequently forming mesoscale-ordered structures and crystallites. The process proceeds until the amorphous precursors are completely consumed, with the transformation kinetics governed by an energy barrier that determines the rate-limiting step. In stage III, stable crystallite nanoparticles form in solution, characterized by a temperature-dependent thermal equilibrium of molecular interactions at the crystal-solution interface. Beyond these core advancements, we explore the influence of encapsulated pepsin and nonencapsulated lysozyme on ZIF-8 formation, finding that their amino acid proton transfer capacity and concentration influence the resulting biomolecule-MOF composite's shape and encapsulation efficiency. The findings contribute to understanding the molecular mechanisms behind biomimetic mineralization and have potential implications for engineering proteins within amorphous MOF nuclei as protein embryo growth sites.

Polyimidazole ligands: Copper(II) complexes and antiproliferative activity in cancer cells

The design of novel chelators for therapeutic applications has been the subject of extensive research to address various diseases. Many chelators can manipulate the levels of metal ions within cells and effectively modulate the metal excess. In some cases, chelators show significant toxicity to cells.We investigated polyimidazole ligands by potentiometry and UV–Vis spectroscopy for their ability to form copper(II) complexes. We also compared the antiproliferative activity of the polyimidazole ligands and their copper(II) complexes with polypyridine ligands in CaCo-2 (colorectal adenocarcinoma), SH-SY5Y (neuroblastoma) and K562 (chronic myelogenous leukemia) cells and normal HaCaT (keratinocyte) cells.Polyimidazole ligands are less cytotoxic than their analogous polypyridine ligands. All polyimidazole ligands, except the tetraimidazole ligand for K562 cells, did not show any significant effect on the viability of cancer and normal cells. In contrast, the cytotoxic activity of polypiridine ligands was also observed in normal cells with IC50 values similar to those of cancer cells.Tetraimidazole ligand, the only ligand active on the leukemic K562 cell line, induced caspase-dependent apoptosis and increased intracellular reactive oxygen species production with mitochondrial damage.The low cytotoxicity of the polyimidazole ligands, even if it limits their use as anticancer agents, could make them useful in other medical applications, such as in the treatment of metal overload, microbial infections, inflammation or neurodegenerative disorders.

Entrance channels to coproheme in coproporphyrin ferrochelatase probed by exogenous imidazole binding

Iron insertion into porphyrins is an essential step in heme biosynthesis. In the coproporphyrin-dependent pathway, specific to monoderm bacteria, this reaction is catalyzed by the monomeric enzyme coproporphyrin ferrochelatase. In addition to the mechanistic details of the metalation of the porphyrin, the identification of the substrate access channel for ferrous iron to the active site is important to fully understand this enzymatic system. In fact, whether the iron reaches the active site from the distal or the proximal porphyrin side is still under debate. In this study we have thoroughly addressed this question in Listeria monocytogenes coproporphyrin ferrochelatase by X-ray crystallography, steady-state and pre-steady-state imidazole ligand binding studies, together with a detailed spectroscopic characterization using resonance Raman and UV–vis absorption spectroscopies in solution. Analysis of the X-ray structures of coproporphyrin ferrochelatase-coproporphyrin III crystals soaked with ferrous iron shows that iron is present on both sides of the porphyrin. The kinetic and spectroscopic study of imidazole binding to coproporphyrin ferrochelatase‑iron coproporphyrin III clearly indicates the presence of two possible binding sites in this monomeric enzyme that influence each other, which is confirmed by the observed cooperativity at steady-state and a biphasic behavior in the pre-steady-state experiments. The current results are discussed in the context of the entire heme biosynthetic pathway and pave the way for future studies focusing on protein-protein interactions.

One-step green synthesis of flower-like non-precious metal (Cu, Ni, Fe or Zn) doped ZIF-67 and its application as non-enzymatic electrochemical glucose sensors

Co ions and imidazolate ligands can be self-assembled into a novel metal-organic frameworks (MOFs) with zeolite-like topological structures, which is named as ZIF-67. Flower-like ZIF-67 can be precisely prepared by one-step green synthesis method under specific experimental conditions, and has excellent enzyme-like electrocatalytic activity toward glucose. Non-precious metal (Cu, Ni, Fe or Zn) can be doped into flower-like ZIF-67 while maintaining zeolite-like topological structures, which may also be an important way to enhance the electrocatalytic performances of ZIF-67. In this study, flower-like non-precious metal (Cu, Ni, Fe or Zn) doped ZIF-67 was contrastively researched by physical characterizations and electrochemical techniques, and was employed as electrocatalysts for non-enzymatic electrochemical glucose sensors. Flower-like non-precious metal (Cu, Ni, Fe or Zn) doped ZIF-67 all exhibits perfect electrocatalytic activities toward glucose, among them the performance of Fe(5 %)-ZIF-67 is the most outstanding.

RETRACTION: A 3D Luminescent Metal‐organic Framework Constructed from Cu4I4 Cubane Clusters and Triangular Imidazole Ligand

AbstractRetraction: S.‐S. Liu, S. Yuan, T.‐P. Hu, D Sun, “A 3D Luminescent Metal‐organic Framework Constructed from Cu4I4 Cubane Clusters and Triangular Imidazole Ligand”, Z. Anorg. Allg. Chem. 2014, 640, 2030–2034, https://doi.org/10.1002/zaac.201400071.The above article, published online on 09 May 2014 in Wiley Online Library (wileyonlinelibrary.com) has been retracted by agreement between the journal Editors‐in‐Chief, Thomas F. Fässler, Christian Limberg, David Scheschkewitz; and Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim. The retraction has been agreed upon following an investigation into concerns raised by a third party which identified unexpected repetitions in two diffractograms presented in figure 3. The authors admitted that they made a mistake and provided partial raw data. However, while new data provided for both experimentally obtained diffractograms for figure 3 show perfect consistency, both diffractograms do not show the identity with the expected diffractogram obtained by the simulation. The editors do not consider the experimental data sufficient to substantiate the presence of the stated compound. As a result, the article‘s conclusions can no longer be considered valid. The authors disagree with the retraction.

Recyclable Homogeneous Catalysis Enabled by Dynamic Coordination on Rhodium(II) Axial Sites of Metal-Organic Polyhedra.

The activity of catalytic nanoparticles is strongly dependent on their surface chemistry, which controls colloidal stability and substrate diffusion toward catalytic sites. In this work, we studied how the outer surface chemistry of nanostructured Rh(II)-based metal-organic cages or polyhedra (Rh-MOPs) impacts their performance in homogeneous catalysis. Specifically, through post-synthetic coordination of aliphatic imidazole ligands onto the exohedral Rh(II) axial sites of Rh-MOPs, we solubilized a cuboctahedral Rh-MOP in dichloromethane, thereby enabling its use as a homogeneous catalyst. We demonstrated that the presence of the coordinating ligand on the surface of the Rh-MOP does not hinder its catalytic activity in styrene aziridination and cyclopropanation reactions, thanks to the dynamic Rh-imidazole coordination bond. Finally, we used similar ligand exchange post-synthetic reactions to develop a ligand-mediated approach for precipitating the Rh-MOP catalyst, facilitating the recovery and reuse of Rh-MOPs as homogeneous catalysts.

Photo-induced imine reduction by a photoredox biocatalyst consisting of a pentapeptide and a Ru bipyridine terpyridine complex

Imine reduction is a useful reaction in the preparation of amine derivatives. Various catalysts have been reported to promote this reaction and photoredox catalysts are promising candidates for sustainable amine synthesis. Improvement of this reaction using biomolecule-based reaction scaffolds is expected to increase the utility of the reaction. In this context, we have recently investigated photoredox Ru complexes with pentapeptide scaffolds via coordination bonds as catalysts for photoreduction of dihydroisoquinoline derivatives. First, Ru bipyridine terpyridine complexes coordinated with five different pentapeptides (XVHVV: X = V, F, W, Y, C) were prepared and characterized by mass spectrometry. Catalytic activities of the Ru complexes with XVHVV were evaluated for photoreduction of dihydroisoquinoline derivatives in the presence of ascorbate and thiol compounds as sacrificial reagents and hydrogen sources. Interestingly, the turnover number of the Ru complex with VVHVV is 531, which is two-fold higher than that of a simple Ru complex with an imidazole ligand. The detailed emission lifetime measurements indicate that the enhanced catalytic activity provided by the peptide scaffold is caused by an efficient reaction with the thiol derivative to accelerate reductive quenching of Ru complex. The quenching behavior suggests formation of an active species such as a Ru(I) complex. These findings reveal that the simple pentapeptide serves as an effective scaffold to enhance the photocatalytic activity of a photoactive Ru complex.

Synthesis, Characterization, and Cytotoxicity Evaluation of Novel Water-Soluble Cationic Platinum(II) Organometallic Complexes with Phenanthroline and Imidazolic Ligands.

Platinum-based chemotherapeutic agents are widely used in the treatment of cancer. However, their effectiveness is limited by severe adverse reactions, drug resistance, and poor water solubility. This study focuses on the synthesis and characterization of new water-soluble cationic monofunctional platinum(II) complexes starting from the [PtCl(η1-C2H4OEt)(phen)] (1, phen=1,10-phenanthroline) precursor, specifically [Pt(NH3)(η1-C2H4OEt)(phen)]Cl (2), [Pt(1-hexyl-1H-imidazole)(η1-C2H4OEt)(phen)]Cl (3), and [Pt(1-hexyl-1H-benzo[d]imidazole)(η1-C2H4OEt)(phen)]Cl (4), which deviate from traditional requirements for antitumor activity. These complexes were evaluated for their cytotoxic effects in comparison to cisplatin, using immortalized cervical adenocarcinoma cells (HeLa), human renal carcinoma cells (Caki-1), and normal human renal cells (HK-2). While complex 2 showed minimal effects on the cell lines, complexes 3 and 4 demonstrated higher cytotoxicity than cisplatin. Notably, complex 4 displayed the highest cytotoxicity in both cancer and normal cell lines. However, complex 3 exhibited the highest selectivity for renal tumor cells (Caki-1) among the tested complexes, compared to healthy cells (HK-2). This resulted in a significantly higher selectivity than that of cisplatin and complex 4. Therefore, complex 3 shows potential as a leading candidate for the development of a new generation of platinum-based anticancer drugs, utilizing biocompatible imidazole ligands while demonstrating promising anticancer properties.

A theoretical study of the electron paramagnetic resonance spectra and local environment in copper(II) complexes with different imidazole and chlorido ligands.

Copper(II) chloride anionic coordination complexes with different imidazole-derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-vis) spectra of [CuCl(C6H10N2)4]Cl, [CuCl(C6H10N2)4]Cl, [CuCl2(C4H6N2)4], and [Cu2Cl2(C5H8N2)6]Cl2·2H2O, the local structure of the corresponding Cu2+ centers and the role of different ligands are obtained. Based on the well-agreed EPR parameters and the d-d transitions (10Dq), the four Cu2+ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper-containing imidazolyl alkyl derivatives.

Tuning Coordination in ZIF-67 Through the Solid-State Thermal Synthesis for Balancing Structural Stability and Catalytic Reactivity.

Tailor-made unsaturated coordination of metal ions or organic linkers in zeolitic imidazole frameworks (ZIFs) has great potential in tuning the ZIFs' properties and reactivity for their applications. Taking advantage of the solid-state thermal (SST) method as a facile and eco-friendly synthesis method, the rational coordination of metal ions with imidazole ligands in ZIF-67 through the SST method is investigated. The rational precursor ratio (metal-to-ligand source) under the solvent-free SST method emerges as a perfect strategy to tune the coordinately unsaturated sites within the ZIF-67 frameworks. Different analysis techniques, computational methods (DFT), and catalytic model reactions examine unsaturated coordination in ZIF-67 materials (defect structures). The unsaturated coordination provides unique characteristic properties on materials with excellent catalytic performance. However, the higher reactive properties are negotiated with weaker structural stability on materials. In addition, the post-SST approach is applied to enable rational coordination and modify the pristine ZIF-67 materials. The post-SST method rearranges and modifies coordination in the framework of materials. These findings are crucial to understanding the role of the uncoordinated degree to balance with structural stability based on ZIF-67, which is critical for effective heterogeneous catalysts.

Catalytic Differences between Flavohemoglobins of Giardia intestinalis and E. coli.

The sole known heme enzyme of the parasitic protist Giardia intestinalis is a flavohemoglobin (gFlHb) that acts as a nitric oxide dioxygenase (NOD) and protects the organism from the free radical nitric oxide. To learn more about the properties of this enzyme, we measured its nitric oxide dioxygenase, NADH oxidase, and cytochrome c reductase activities and compared these to the activities of the E. coli flavohemoglobin (Hmp). The turnover number for the NOD activity of gFlHb (23 s-1) is about two-thirds of that of Hmp (34 s-1) at pH 6.5 and 37 °C. The two enzymes differ in their sensitivity towards molecules that act as heme ligands. For both gFlHb and Hmp, inhibition with miconazole, a large imidazole ligand, is adequately described by simple competitive inhibition, with KI = 10 μM and 0.27 μM for gFlHb and Hmp, respectively. Inhibition plots with the small ligand imidazole were biphasic, which is consistent with previous experiments with carbon monoxide as a probe that show that the active site of flavohemoglobins exists in two conformations. Interestingly, the largest difference is observed with nitrite, which, like imidazole, also shows a biphasic inhibition plot; however, nitrite inhibits gFlHb at sub-millimolar concentrations while Hmp is not significantly affected. NADH oxidase activity measured under aerobic conditions in the absence of nitric oxide for Hmp was more than twice the activity of gFlHb. The addition of 1 mM hydrogen peroxide in these assays stimulated the NADH oxidase activity of gFlHb but not Hmp. Both enzymes had nearly identical cytochrome c reductase activities but the extent of the contribution of indirect reduction by flavohemoglobin-generated superoxide was much lower with gFlHb (4% SOD-inhibited) than with Hmp (17% SOD-inhibited). Although the active sites of the two enzymes share the same highly conserved residues that are important for catalysis, differences in the distal ligand binding site may account for these differences in activity and sensitivity towards NOD inhibitors. The differences observed in the NADH oxidase and cytochrome c reductase assays suggest that gFlHb may have evolved to protect the protist, which lacks both superoxide dismutase and catalase, from the damaging effects of superoxide by minimizing its production and from peroxide by actively reducing it.

(2,5-Di-methyl-imidazole){N,N',N'',N'''-[porphyrin-5,10,15,20-tetra-yltetra-(2,1-phenyl-ene)]tetra-kis(pyridine-3-carboxamide)}manganese(II) chloro-benzene disolvate.

In the title compound, [Mn(C68H44N12O4)(C5H8N2)]·2C6H5Cl, the central MnII ion is coordinated by four pyrrole N atoms of the porphyrin core in the basal sites and one N atom of the 2,5-di-methyl-imidazole ligand in the apical site. Two chloro-benzene solvent mol-ecules are also present in the asymmetric unit. Due to the apical imidazole ligand, the Mn atom is displaced out of the 24-atom porphyrin mean plane by 0.66 Å. The average Mn-Np (p = porphyrin) bond length is 2.143 (8) Å, and the axial Mn-NIm (Im = 2,5-di-methyl-imidazole) bond length is 2.171 (8) Å. The structure displays inter-molecular and intra-molecular N-H⋯O, N-H⋯N, C-H⋯O and C-H⋯N hydrogen bonding. The crystal studied was refined as a two-component inversion twin.

Sulfadiazine detection in aquatic products using upconversion nanosensor based on photo-induced electron transfer with imidazole ligands and copper ions

Contamination of aquatic products with sulfonamide antibiotics poses a threat to consumer health and can lead to the emergence of drug-resistant bacteria. Common methods to detect such compounds are slow and require expensive instruments. We developed a sensitive sulfadiazine (SDZ) detection method based on the photoinduced electron transfer between UCNPs and Cu2+. The surface-modified upconversion nanoparticles bind to Cu2+ by electrostatic adsorption, causing fluorescence quenching. The quenched fluorescence was subsequently recovered by the addition of imidazole and SDZ to the detection system, which formed a complex with Cu2+. The sensor showed excellent linearity over a wide concentration range (0.05–1000 ng/mL), had a low limit of detection (0.04 ng/mL), was selective, and was not affected by common substances present in aquatic media. This indicates that the sensor has great potential for application in the detection of SDZ residues in aquatic products.

In-silico green toxicology approach toward discovering safer ligands for development of safe-by-design metal–organic frameworks

A vast variety of chemical compounds have been fabricated and commercialized, they not only result in industrial exposure during manufacturing and usage, but also have environmental impacts throughout their whole life cycle. Consequently, attempts to assess the risk of chemicals in terms of toxicology have never ceased. In-silico toxicology, also known as predictive toxicology, has advanced significantly over the last decade as a result of the drawbacks of experimental investigations. In this study, ProTox-III was applied to predict the toxicity of the ligands used for metal–organic framework (MOF) design and synthesis. Initially, 35 ligands, that have been frequently utilized for MOF synthesis and fabrication, were selected. Subsequently, canonical simplified molecular-input line-entry system (SMILES) of ligands were extracted from the PUBCHEM database and inserted into the ProTox-III online server. Ultimately, webserver outputs including LD50 and the probability of toxicological endpoints (cytotoxicity, carcinogenicity, mutagenicity, immunotoxicity, and ecotoxicity) were obtained and organized. According to retrieved LD50 data, the safest ligand was 5-hydroxyisophthalic. In contrast, the most hazardous ligand was 5-chlorobenzimidazole, with an LD50 of 8 mg/kg. Among evaluated endpoints, ecotoxicity was the most active and was detected in several imidazolate ligands. This data can open new horizons in design and development of green MOFs.