Stability Of Metal Complexes Research Articles

Synthesis, characterization, thermal properties, antimicrobial evaluation, ADMET study, and molecular docking simulation of new mono Cu (II) and Zn (II) complexes with 2-oxoindole derivatives

One of the interesting research fields is developing and assessing novel metal-containing medications. A new isatin-3-thiosemicarbazone derivative 4 was synthesized by two different methods based on hydrazone derivatives 2 and 3. Additionally, the chelation of thiosemicarbazone with copper (II) and zinc (II) forms a monobasic tridentate (ONS) complex with two five-member rings and a tetrahedral geometry structure. The structure of synthesized complexes was characterized using elemental analysis, FT-IR, mass spectra, and 1H/13C NMR. Thermogravimetric analysis revealed the upgrading of the thermal stability of metal complexes compared to their thiosemicarbazone ligand. The stoichiometric ratio of the coordination confirmed the formation of 1:1 (M: L) stoichiometry. In vitro antimicrobial activity was screened against two gram-positive, two gram-negative, and one fungal strain. Both ligand 4 and Zn complex 6 displayed high antimicrobial activity compared with copper complex 5 based on the zone of inhibition. Further, MIC and MBC were determined for both zinc and ligand. The zinc complex 6 displayed excellent antimicrobial activity with (MIC = 3.9–27.77 μg/mL) against bacterial strains and (MIC = 7.81 μg/mL) against C. albicans, as well as exhibited MBC values ranging between (MBC = 6.51–45.58 μg/mL) and (MFC = 13.58 μg/mL), respectively, and demonstrated bactericidal and fungicidal behavior. The in-silico ADMET study for ligand and two complexes were determined and showed non-AMES toxicity, non-carcinogenic, and obey the rule of five. A comparative docking study provided more insight into the binding mechanisms and suggested that antimicrobial activity may be due to inhibition of different targets.

On the evaluation of the intrinsic stability of indium-nanoparticulate organic matter complexes

HypothesisProper evaluation of the intrinsic stability of metal complexes with humic nanoparticles calls for a robust representation of the particulate electrostatic features. Addressing here the case of trivalent metal association with humics for which a significant electrostatic contribution is expected, we report a robust interpretative approach as an alternative to the conventional but approximative Donnan model applied in popular speciation codes. ExperimentsThe intrinsic chemical binding affinity of Indium to humic nanoparticles is addressed from equilibrium electroanalytical measurements (Absence of Gradient and Nernstian Equilibrium Stripping) in NaClO4 electrolyte (10–100 mM, pH4) at different metal-to-humics concentration ratios. The electrostatic contribution was evaluated using a Poisson-Boltzmann based-approach where the key electrostatic descriptors of humics are involved. FindingsThe electrochemical results interpreted in the light of so identified non-specific indium binding contribution evidences a dramatic impact of electrostatics on indium complexation by humics, with e.g. in 10 mM electrolyte an intraparticulate Boltzmann metal accumulation factor that is ca. 5 times larger than that reported for cadmium and highly-charged fulvics complexants. A successful comparison between theory and experiments is consistently achieved over the tested electrolyte concentrations with the only adjustment of the radius of the metal accumulation spherical volume. The analysis reveals the necessity to consider full equilibration of charged humics with its intraparticulate counterion atmosphere.

Hydroxypyridinone-Based Metal Chelators towards Ecotoxicity: Remediation and Biological Mechanisms.

Hydroxypyridinones (HPs) are recognized as excellent chemical tools for engineering a diversity of metal chelating agents, with high affinity for hard metal ions, exhibiting a broad range of activities and applications, namely in medical, biological and environmental contexts. They are easily made and functionalizable towards the tuning of their pharmacokinetic properties or the improving of their metal complex thermodynamic stabilities. In this review, an analysis of the recently published works on hydroxypyridinone-based ligands, that have been mostly addressed for environmental applications, namely for remediation of hard metal ion ecotoxicity in living beings and other biological matrices is carried out. In particular, herein the most recent developments in the design of new chelating systems, from bidentate mono-HP to polydentate multi-HP derivatives, with a structural diversity of soluble or solid-supported backbones are outlined. Along with the ligand design, an analysis of the relationship between their structures and activities is presented and discussed, namely associated with the metal affinity and the thermodynamic stability of the corresponding metal complexes.

Synthesis, characterization, thermal studies, electrochemical behavior, antimicrobial, docking studies, and computational simulation of triazole‐thiol metal complexes

AbstractIn this study, we elucidate the structure and molecular properties of triazole‐thiol derivative (HL) which is confirmed via B3LYP/6‐31G(d) for DFT and HF basis set. Triazole‐thiol (HL) was conjugated with several metal ions to afford stable metal complexes. Consequently, confirmed via intensive physicochemical analysis including FT‐IR spectra, elemental analysis, electronic, 1H‐NMR, TGA, and DTA. The explanation of the thermal cracking of these metal complexes has been estimated. The FT‐IR of these complexes indicated the presence of triazole‐thiol ligand (HL) as chelated coordinated through the N atom of amino group and S atom of SH moiety. Furthermore, Fe(III) complex and Ni(II) adopt octahedral stereochemistry, while the Cu(II) complex is trigonal bipyramidal, and Cd(II) complex is square planar. Thermal investigation maintained the chemical formulation of these metal complexes and exhibited that they decompose in many stages dependent on the kind of ligand and geometry of complexes. Moreover, the HL and metal complexes were exhibited antimicrobial evaluation against bacterial and fungal strains and showed higher activity comparable HL. Additionally, the theoretical docking stimulation of the ligand HL and metal complexes with different proteins showed different in energy affinity with shortage bond length with metal complexes and confirmed the experimental biological results. Eventually, the electrochemical features were explored utilizing cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Manganese-Catalyzed Reformation of Vicinal Glycols to α-Hydroxy Carboxylic Acids with the Liberation of Hydrogen Gas

Conversion of readily available feedstocks to valuable platform chemicals via an eco-friendly catalytic pathway has always been one of the key focuses of synthetic chemists. In this context, herein, we report selective transformation of readily available feedstock, vicinal glycols, to value-added α-hydroxycarboxylic acid molecules that are prevalent in bioactive molecules and biodegradable polymers. A bench stable Earth-abundant metal complex, {[HN(C2H4PPh2)2]Mn(CO)2Br}, Mn-I catalyzed the reformation reaction at low temperature in high selectivity with a turnover number reaching 2400, surpassing previously used homogeneous catalysts for such a reaction. Hydrogen gas is evolved as a byproduct without needing an acceptor. The developed protocol is applicable for both aromatic and aliphatic vicinal glycols, delivering the α-substituted hydroxycarboxylic acids in high yields and selectivities. Detailed mechanistic studies elucidated the involvements of different manganese(I)-species during this acceptorless dehydrogenation catalysis.

Synthesis, anti‐proliferative activities, docking studies, and computational calculations of novel isonicotinic mixed complexes

AbstractIn this investigation, we studied the mixing of two ligands, isonicotinohydrazide (L1) and 3‐hydroxyisonicotinic acid (L2), with different metal ions to afford the corresponding stable metal complexes. Consequently, intensive physico‐chemical analysis including elemental analysis, UV–visible, Fourier transform infrared (FT‐IR), thermogravimetric analysis (TGA), mass, 1H nuclear magnetic resonance (NMR), X‐ray diffraction (XRD), magnetic, and molar conductance measurements has been performed. The thermal stability of all complexes was determined using TGA, and the kinetic parameters were obtained using the Coats–Redfern method. Both the degree of crystallinity and the unit cell of all complexes were determined utilizing XRD studies. Furthermore, these metal complexes exhibited excellent anti‐proliferative activity against human breast cancer (MCF‐7) and human liver cancer (HepG2) cell lines against the doxorubicin drug. The Co(II) complex outperformed all other metal complexes in terms of activity, which was confirmed by molecular docking stimulation via the binding energy with amino acids in a structural complex of Kaposi's sarcoma‐associated herpesvirus (KSHV) thymidylate synthase (PDBID:5H38) and the ternary complex of KRIT1 bound to both the Rap1 GTPase and the Heart of Glass (HEG1) cytoplasmic tail (PDBID:4hdq) and shortage. Moreover, these metal complexes were optimized via theoretical investigation through a density functional theory (DFT)/B3LYP/LANL2DZ basis set to confirm the stability of these metals theoretically and detect frontier molecular orbitals (FMO), electrostatic potential (ESP), energy gap, and physical computational calculations. Eventually, the electrochemical features were explored using cyclic voltammetry (CV) and electrochemical impedance spectra (EIS).

M(II) (M=Cu, Ni) Assisted C−S Bond Cleavage and Oxidative Dehydrogenation of Amine on Non‐Innocent Salen Type Ligand Platforms by Varying Nitrogen vs. Sulfur Coordination Atoms

AbstractHerein, we report two newly synthesized salen‐type ligands, 2,3‐bis((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)thio)maleonitrile (H2L1) and 2,3‐bis((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)amino)malenonitrile (H4L2), bearing different coordination sites (sulfur vs amine) at maleonitrile tethered moiety to investigate metal mediated non‐innocence chemistry of these ligands. Upon metallation, ligand H2L1 did not yield simple metal‐ligand complex, rather ligand was split into two organic fragments, dithiolene moiety (mnt)2− and phenol moiety via C−S bond cleavage wherein (mnt)2− formed a stable metal complex [M(mnt)2]2−. The C−S bond cleavage was interpreted in terms of strong p(π) … d(π) interaction between metal and dithiolene moiety in H2L1 ligand that invoked the intramolecular rearrangement facilitating C−S bond cleavage. Interestingly, the phenol moiety further transformed to either unprecedented 2,4‐di‐tert‐butyl‐6‐methylenecyclohexa‐2,4‐dienone (i. e. spiro compound; 5) or 2,4‐di‐tert‐butyl‐6‐(hydroxymethyl)phenol (6) depending on the temperature of reaction and type of metal ion used which was further predicted using DFT calculation. On the other hand, combined experimental and DFT studies explained that upon metallation, ligand H4L2 yielded non‐cleavage [M(H2L2)] (3 for M=Cu(II) and 4 for M=Ni(II) ) complex, which slowly oxidized at −NH−CH2‐(amine) region to −N=CH− (imine) in H2L2 ligand under aerobic environment via C−H bond activation, yielding [CuII(L3)] (1) (or [NiII(L3)] (2) complex (H2L3=oxidatively dehydrogenated product of H4L2 ligand.

Spectral study of the structure and properties of complexes of unsubstituted indoline spiropyran with aluminum ions

The methods of absorption electronic and NMR spectroscopy were used to study the processes of complexation during the interaction of molecules of unsubstituted indoline spiropyran with aluminum salts. The mechanism of formation and structure of complexes of two types has been established. Negative photochromism of the complex of the merocyanine form of spiropyran with aluminum ions was found. The stability of metal complexes to the action of various agents has been investigated. Keywords: photochromism, spiropyrans, metal complexes, aluminum salts, electron spectroscopy, NMR spectroscopy.

Antimicrobial, Cytotoxicity and Molecular Docking Study of New Quinoline Schiff Base and its Metal(II) Complexes

A new quinoline Schiff base ligand was synthesized by the reaction of 2-hydroxy-7-methylquinolin- 3-carbaldehyde and 4-methylbenzene sulfonohydrazide. Synthesized Schiff base further utilized for the formation of stable metal complexes with Cu(II), Ni(II), Co(II) and Cd(II) metal salts and characterized by different spectroscopic techniques i.e. 1H NMR, 13C NMR, FT-IR, UV-visible, ESR, MASS and TGA. The low molar conductance values indicate that synthesized metal(II) complexes were non-electrolytes. The magnetic moment value indicates that Cu(II), Ni(II) and Co(II) complexes were paramagnetic. Further, these compounds were screened for inhibition activity against four bacterial strains, three fungal strains and cytotoxicity against the A-549 and MCF-7 cell lines by using the MTT method. Among the synthesized complexes, metal complexes exhibited excellent anticancer activity against the human lung cancer cell line (A-549). Schiff base and its Cd(II) complex showed good antibacterial activity. Furthermore, molecular docking study shows the significant binding affinity of metal complexes with tubulin protein. Present study proposed that all the synthesized Schiff base metal(II) complexes have excellent biological activity and could be act as potential anticancer agents.

How different are the surfaces of semiconductor Ag2Se quantum dots with various sizes?

The surface of nanocrystals plays a dominant role in many of their physical and chemical properties. However, controllability and tunability of nanocrystal surfaces remain unsolved. Herein, we report that the surface chemistry of nanocrystals, such as near-infrared Ag2Se quantum dots (QDs), is size-dependent and composition-tunable. The Ag2Se QDs tend to form a stable metal complex on the surface to minimize the surface energy, and therefore the surface chemistry can be varied with particle size. Meanwhile, changes in surface inorganic composition lead to reorganization of the surface ligands, and the surface chemistry also varies with composition. Therefore, the surface chemistry of Ag2Se QDs, responsible for the photoluminescence (PL) quantum yield and photostability, can be tuned by changing their size or composition. Accordingly, we demonstrate that the PL intensity of the Ag2Se QDs can be tuned reversely by adjusting the degree of surface Ag+ enrichment via light irradiation or the addition of AgNO3. This work provides insight into the control of QD surface for desired PL properties.

Effect of Metal Sequestrants on the Decomposition of Hydroxylammonium Nitrate

Hydroxylammonium nitrate (HAN) is an energetic salt used in flight-proven green monopropellants such as ASCENT (formerly AF-M315E), flown in NASA’s 2019 Green Propellant Infusion Mission, and SHP163, flown in JAXA’s Rapid Innovative Satellite Technology Demonstration-1. The decomposition of HAN is catalyzed by metals commonly found in storage tanks, a factor limiting its use. This work investigates the ability of metal-sequestering chelating agents to inhibit the decomposition of HAN. Isothermal and dynamic thermogravimetric analysis (TGA) were used to find isothermal decomposition rates, decomposition onset temperatures, and first-order Arrhenius reaction rate parameters. In the present research, 2,2′-bipyridine (Bipy), triethanolamine (TEA), and ethylenediaminetetraacetic acid (EDTA) were studied as 0.05, 0.1, 0.5, 1, and 5% by weight additives in 90% aqueous HAN. An isothermal decomposition rate of 0.137%/h at 348 K was observed for HAN. The addition of 1% Bipy and 1% TEA reduced the isothermal decomposition rate by 20.4% to 0.109%/h, and by 3.65% to 0.132%/h, respectively, showing that Bipy can inhibit decomposition. The addition of 1% EDTA increased the isothermal decomposition rate by 12.4% to 0.154%/h. Bipy was found to increase the decomposition onset temperature from 454.8 K to 461.8 K, while the results for TEA and EDTA were inconclusive. First order reaction rates calculated by the Ozawa-Flynn-Wall method were found to be insufficient to capture the effects of the tested additives. Bipy was found to inhibit the decomposition of HAN, while TEA and EDTA produced little or negative effect, a result believed to be due to poor metal complex stability at low pH and high acidity, respectively. Spectrophotometry, used for colorimetric analysis of Bipy+iron complexes, showed that Bipy forms chelate complexes with trace iron impurities when added to HAN solutions.

New complexes of gadolinium with dicarboxylate diphosphabetaines

The processes of complexation of dicarboxylate diphosphabetaines with gadolinium nitrate were studied, as a result of which stable polymer metal complexes insoluble in inorganic and organic solvents were obtained. To carry out these reactions, dicarboxylate diphosphabetaines were previously synthesized: 3,3'-(propane-1,3-diylbis (diphenyl)phosphoniondiyl)dipropanoate and 3,3'-(hexane-1,3-diylbis (diphenyl)phosphoniondiyl)dipropanoate, based on maleic acid with 1,3-bis(diphenylphosphino)bisphosphinspropane and 1,6-bis(diphenylphosphino)bisphosphinshexane. The structure of dicarboxylate diphosphabetaines and poly-nuclear polymer complexes of gadolinium has been confirmed by modern physical and chemical methods of research, including NMR and IR spectra, elemental and X-ray structural analysis, thermal stability has been studied by simultaneous thermogravimetry and differential scanning calorimetry.

Noncovalent Interactions in Organometallic Chemistry: From Cohesion to Reactivity, a New Chapter.

Noncovalent interactions (NCIs) have long interested a vast community of chemists who investigated their "canonical categories" derived from descriptive crystallography, e.g., H-bonds, π-π interactions, halogen/chalcogen/tetrel bonds, cation-π and C-H-π interactions, metallophilic interactions in the broad sense, etc. Recent developments in theoretical chemistry have enabled the treatment of noncovalent interactions under new auspices: dispersion-force-inclusive density functionals have emerged, which are reliable for modeling small to large molecular systems. It is possible to perform the full analysis of the contributions of London, Debye, and Keesom forces, i.e., the main components of van der Waals forces, by the DFT-D and ab initio methods at a reasonable computational cost. Our research has been focusing for now 15 years on the role of NCIs in the cohesion of organometallic complexes. NCIs are not only effective in Werner's secondary coordination sphere but also in the metal's primary one. The stabilization of electron-unsaturated transition metal complexes by hemichelation, metal-metal donor-acceptor complexes, and self-aggregation of cationic Rh(I) chromophores have indeed outlined the significance of the London dispersion force as an attractive force operating throughout the whole molecule or molecular assembly. The recent outburst of interest in C-H bond functionalization led us to address the broader question of reaction and catalyst engineering: although one can now satisfactorily analyze bonding and molecular cohesion in transition-metal-based organometallic systems, can modern theoretical methods guide reactivity exploration and the engineering of novel catalytic systems? We addressed this question by investigating the ambiphilic metal-ligand activation/concerted metalation-deprotonation mechanism involved in transition-metal-catalyzed directed C-H bond functionalization. This endeavor was initiated having in scope the construction of a rationale for the transposition of 4-5d metal chemistry to earth-abundant 3d metals. In this base-assisted mechanism of C-H bond metalation, agostic interactions are necessary but not sufficient because C-H bond breaking actually relies on the attractive NCI coding of a proton-transfer step and the minimization of metal-H repulsion. This Account introduces the recent shift of our research toward the construction of an NCI-inclusive paradigm of chemical reactivity engineering based on experimental efforts propped up by state-of-the-art theoretical tools.

Synthesis and Structural and Spectroscopic Studies of a pH-Neutral Argentic Chelate Complex: Tribasic Silver (III) Bisperiodate.

The preparation of stable hypervalent metal complexes containing Ag(III) has historically been challenging due to their propensity for reduction under ambient conditions. This work explores the preparation of a tripotassium silver bisperiodate complex as a tetrahydrate via chemical oxidation of the central silver atom and orthoperiodate chelation. The isolation of the chelate complex in high yield and purity was achieved via acidimetric titration. The comprehensive physiochemical characterization of the tribasic silver bisperiodate included single crystal X-ray diffraction, thermogravimetric and differential scanning calorimetry, and infrared and ultraviolet–visible spectroscopy. Infrared and UV–visible absorption spectra (λmax 255 and 365 nm) were in good agreement with historically prepared pentabasic diperiodatoargentate chelate complexes. The C2/c monoclinic distorted square planar structure of the bis-chelate complex affords a mutually supportive framework to both Ag(III) and I(VII), conferring stability under both thermal and long-term ambient conditions. Thermal analysis of the tribasic silver bisperiodate complex identified an endothermic mass loss, ΔH = +278.35 kJ/mol, observed at 139.0 °C corresponding to a solid-state reduction of silver from Ag(III) to Ag(I). Under ambient conditions, no significant degradation was observed over a 12 month period (P = 0.30) for the silver bisperiodate complex in a solid state, with an observed half-life of τ1/2 = 147 days in a pH-neutral aqueous solution.

Spectroscopic, quantum chemical calculations, antioxidant, anticancer, antimicrobial, DNA binding and photo physical properties of bioactive Cu(II) complexes obtained from trifluoromethoxy aniline Schiff bases

In this study, new three Schiff base ligands and their Cu(II) complexes: 1 [Cu(L1)2], 2 [Cu(L2)2] and 3 [Cu(L3)2], where HL1-HL3 represent Schiff base ligands (HL1 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-6‑chloro-4-fluorophenol, HL2 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-3,5-dimethoxy-phenol and HL3 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-5-(diethylamino)phenol) were synthesized. The structural features were confirmed from their micro analytical, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), UV–visible, mass, magnetic susceptibility measurements, ESR and thermal analysis. The spectroscopic approaches proposed a square planar geometry for all Cu(II) complexes. The stability of the binary metal(II) complexes has been calculated from quantum chemical parameters using highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies. All the tested complexes preferably bind to CT-DNA via intercalation mode as resulted from UV spectroscopy and EB competition assay studies. In addition, the metal complexes exhibited good cleavage ability against the pBR322 DNA in the presence and absence of H2O2 as well as UV light. The antioxidant activity of 1–3 was evaluated by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical with reference of ascorbic acid. Of these, complex 1 show good antioxidant activity. The in vitro cytotoxicity studies of the ligands and their complexes against human lung (A549) and breast (MCF7) cancer cell lines showed significant activity. The Schiff base ligands and their metal complexes were screened for their biological activities and are found to be the complexes have higher activities than the free Schiff bases.

Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes

Sterically bulky β-diketiminate (or Nacnac) ligand systems have recently shown the ability to kinetically stabilize highly reactive low-oxidation state main group complexes. Metal halide precursors to such systems can be formed via salt metathesis reactions involving alkali metal complexes of these large ligand frameworks. Herein, we report the synthesis and characterization of lithium and potassium complexes of the super bulky anionic β-diketiminate ligands, known [TCHPNacnac]− and new [TCHP/DipNacnac]− (ArNacnac = [(ArNCMe)2CH]−) (Ar = 2,4,6-tricyclohexylphenyl (TCHP) or 2,6-diisopropylphenyl (Dip)). The reaction of the proteo-ligands, ArNacnacH, with nBuLi give the lithium etherate compounds, [(TCHPNacnac)Li(OEt2)] and [(TCHP/DipNacnac)Li(OEt2)], which were isolated and characterized by multinuclear NMR spectroscopy and X-ray crystallography. The unsolvated potassium salts, [{K(TCHPNacnac)}2] and [{K(TCHP/DipNacnac)}∞], were also synthesized and characterized in solution by NMR spectroscopy. In the solid state, these highly reactive potassium complexes exhibit differing alkali metal coordination modes, depending on the ligand involved. These group 1 complexes have potential as reagents for the transfer of the bulky ligand fragments to metal halides, and for the subsequent stabilization of low-oxidation state metal complexes.

Synthesis and spectral characterization of new azo dye derived from benzimidazole and its complexation with selected transition metal ions

The preparation and spectral characterisation of 2-[6-(benzimidazolylazo)] as an organic heterocyclic azo dye compound containing benzimidazole. The reaction of benzimidazole diazoniumbromid with 2,4-dibromo phenol in alkaline alcoholic solution yielded -2,4-dibromo phenol (BIADBrP). Spectral analyses have been used to study the structure of the azo dye ligand such as H1NMR, mass spectrum,IR, UV-Vis and element analysis. New six complexes with CO(III), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) ions were prepared and identification by several physiochemical techniques; such as C.H.N element, magnatic susceptibility, atom absorption, molar conductivity, IR and electronic spectra. The used techniques showed the formation of all complexes 1:2 [M:L] complexes and suggested octahedral geometry with d2sp3 hybridization of Co(III) and sp3d2 with residulechelat complexes. The coordination number of the metal ion is found to be six with binding through the phenolate O, azo N3 and with the imidazole N3 atom. The stability, geometrical, and electrical features of metal complexes have also been studied theoretically. The energy levels of the ligand and metal complexes’ high occupied molecular orbital HOMO and low unoccupied molecular orbital LUMO were used to compute electrochemical potential, electrophilicity index, and chemical hardness.

Thermally Stable Rare-Earth Metal Complexes Supported by Chelating Silylene Ligands

Thermally Stable Rare-Earth Metal Complexes Supported by Chelating Silylene Ligands

Stability of Metronidazole and Its Complexes with Silver(I) Salts under Various Stress Conditions.

Metronidazole is a drug widely used in the prevention and treatment of bacterial infections. Due to its possibility of the formation of stable metal complexes, it was decided to broaden its activity spectrum by introducing the silver(I) coordination compounds i.e., [Ag(MTZ)2NO3] and [(Ag(MTZ)2)2]SO4, which have significant antibacterial properties. The paper presents a description of a new qualitative and quantitative analysis of metronidazole in bulk and possible pharmaceutical preparations by thin-layer chromatography with densitometric detection. Optimal separation conditions were selected, and the analytical procedure was validated according to the ICH guidelines. The obtained data indicate that the method is sufficiently sensitive, precise, and accurate. The stability of the metronidazole solutions obtained from tablets, pure metronidazole, and its silver(I) complexes was tested. The research was carried out in various environments, at different temperatures, in H2O2 solution, and during exposure to radiation (UV, sunlight). The greatest degradation was found in the alkaline environment and at higher temperatures. The silver(I) complexes exhibited relatively high stability under analyzed conditions that are higher than standard metronidazole solutions and tablets. The observations were confirmed by the kinetic and thermodynamic analysis. The described studies of new metronidazole silver(I) complexes increase the potential for their application in infections both in humans and animals.

E4 Transfer (E=P, As) to Ni Complexes.

The use of [Cp′′2Zr(η1:1‐E4)] (E=P (1 a), As (1 b), Cp′′=1,3‐di‐tert‐butyl‐cyclopentadienyl) as phosphorus or arsenic source, respectively, gives access to novel stable polypnictogen transition metal complexes at ambient temperatures. The reaction of 1 a/1 b with [CpRNiBr]2 (CpR=CpBn (1,2,3,4,5‐pentabenzyl‐cyclopentadienyl), Cp′′′ (1,2,4‐tri‐tert‐butyl‐cyclopentadienyl)) was studied, to yield novel complexes depending on steric effects and stoichiometric ratios. Besides the transfer of the complete En unit, a degradation as well as aggregation can be observed. Thus, the prismane derivatives [(Cp′′′Ni)2(μ,η3:3‐E4)] (2 a (E=P); 2 b (E=As)) or the arsenic containing cubane [(Cp′′′Ni)3(μ3‐As)(As4)] (5) are formed. Furthermore, the bromine bridged cubanes of the type [(CpRNi)3{Ni(μ‐Br)}(μ3‐E)4]2 (CpR=Cp′′′: 6 a (E=P), 6 b (E=As), CpR=CpBn: 8 a (E=P), 8 b (E=As)) can be isolated. Here, a stepwise transfer of En units is possible, with a cyclo‐E4 2− ligand being introduced and unprecedented triple‐decker compounds of the type [{(CpRNi)3Ni(μ3‐E)4}2(μ,η4:4‐E′4)] (CpR=CpBn, Cp′′′; E/E′=P, As) are obtained.