Search Results (115)

Although CH…O hydrogen bonds are generally very weak, here investigated CH…O interactions of coordinated 1,10-phenanthroline (phen) are very frequent and quite strong. In the crystal structures from the Cambridge Structural Database, 8344 CH…O interactions between coordinated phen and water molecule in the second coordination sphere were found. We calculated all possible types of CH…O interaction energies at DLPNO-CCSDT/CBS level for non-coordinated and coordinated phen with a water molecule. The data for non-coordinated phen exhibited the weakest interactions, from −2.09 to −2.94 kcal/mol. Upon coordination of phen, interactions become stronger. In octahedral cobalt(II) complexes, interaction energies are from −3.37 to −4.35 kcal/mol. With the decrease in the complex coordination number, interaction energies become stronger, the strongest are for square planar palladium(II) complexes from −3.91 to −4.94 kcal/mol. There is a linear correlation between interaction energies and electrostatic potential values at the interacting hydrogen atom, with a correlation coefficient of 0.97. For all studied systems, the weakest is always a linear interaction, and the strongest is a bifurcated interaction. The strongest calculated CH…O interactions of coordinated phen with water in the second coordination sphere (−4.94 kcal/mol) are as strong as the hydrogen bond between two water molecules (−5.0 kcal/mol). Full article

Several nickel dichloride phosphine complexes have been synthesized, their crystalline structure determined, and their behavior, in combination with methylaluminoxane, in the polymerization of butadiene has been examined. High-cis polybutadienes were consistently obtained, regardless of the nature of the phosphine coordinated to the metal and the methylaluminoxane/Ni molar ratio used, contrary to what was previously observed in the polymerization of butadiene with analogous cobalt phosphine complexes, in which catalytic selectivity was found to be strongly influenced by these two factors. An interpretation for such different behavior is provided. Full article

Heterobimetallic iron–group 9 carbonyl cations, FeM(CO)_n⁺ (M = Rh, Ir; n = 9–11), were generated in the gas phase via pulsed laser vaporization within a supersonic expansion and characterized by infrared photodissociation spectroscopy in the carbonyl stretching region. By combining experimental spectra with density functional theory simulations, the geometric and electronic structures of these clusters were unambiguously assigned. Mass spectrometry and photodissociation results identified FeM(CO)₉⁺ as the saturated species for M = Rh and Ir, in contrast to the lighter cobalt analog FeCo(CO)₈⁺. The FeM(CO)₉⁺ cations adopt a C_4v-symmetric singlet ground-state structure with all carbonyl ligands terminally bound, corresponding to a (OC)₅Fe–M(CO)₄ configuration. These complexes can be formally described as combination products of the stable neutral Fe(CO)₅ and cationic M(CO)₄⁺ fragments. Analyses based on canonical molecular orbitals, Mayer bond orders, and fragment-based correlation diagrams reveal the presence of a dative Fe→M interaction in FeM(CO)₉⁺, which formally enables the heavier Rh/Ir metal center to attain an 18-electron configuration. However, this bond is weaker than a typical covalent single bond, as the key molecular orbitals involved possess antibonding character. This study provides important insights into the structure and bonding of heteronuclear transition metal carbonyl clusters, highlighting distinctive coordination behavior between late 3d and heavier 4d/5d congeners. Full article

The reaction of CoCl₂ · 6H₂O with 6-chloro-2-hydroxypyridine (Hchp) and 1,10-phenanthroline (phen) afforded the complex [Co(chp)₂(phen)] (1). Although this complex has been previously reported, it was obtained in this work under mild conditions (in acetonitrile at room temperature) and characterized for the first time by single-crystal X-ray diffraction. The use of Co(F₃CCOO)₂ · 4H₂O under similar conditions yielded a new trinuclear molecular complex [Co₃(chp)₂(F₃CCOO)₄(phen)₂] (2). According to X-ray diffraction data, the cobalt(II) ions in complexes 1 and 2 are located in an octahedral environment (coordination number CN_Co = 6). As an ambidentate ligand, Hchp exhibits different types of coordination modes in the resulting complexes 1 and 2. Additional stabilization of molecules in the crystal is achieved by π-π stacking between aromatic systems of coordinated phen ligands. The cytotoxic activity of 1 and [CoCl₂(phen)₂] · 1.5MeCN (3) against a panel of human cancer cell lines (SKBR3, HCT116, A549) and normal dermal fibroblasts (HDF) was evaluated using the MTT assay. Complex 3 demonstrated cytotoxic activity against the HCT116 cell line comparable to that of cisplatin, indicating its potential as a promising antitumor agent. Full article

A series of five cobalt(II) complexes, dichloro-bis(1-benzyl-benzimidazole)-cobalt(II) (1a), dichloro-bis[1-(4-fluorobenzyl)-benzimidazole]-cobalt(II) (1b), dichloro-bis((Z)-1-styryl-benzimidazole)-cobalt(II) (1c), dichloro-bis[(Z)-1-(2-fluorostyryl)-benzimidazole]-cobalt(II) (1d) and dichloro-bis(1-cinnamyl-benzimidazole)-cobalt(II) (1e), were evaluated in ethylene dimerization. Four of these complexes were described for the first time and fully characterized by IR, elemental analysis, mass and NMR spectroscopy. In the solid state, the cobalt atom exhibited a typical tetrahedral geometry and was found to be coordinated to two chlorine atoms and two benzimidazole rings. In the presence of 20 bar of ethylene and diethylaluminium chloride as a co-catalyst, the complex with styryl substituents on the benzimidazole rings, complex 1c, exhibited the highest activity with a turnover frequency of 3430 mol(ethylene)·mol(Co)⁻¹·h⁻¹. Full article

This research prepared and characterised novel mixed coordination complexes derived from escitalopram with eugenol and curcumin to form (L₁) and (L₂), respectively. The complexes were prepared via Williamson ether synthesis and analysed by FTIR, UV–Vis, ¹H-NMR spectroscopy, elemental analysis, molar conductivity, and magnetic susceptibility. The results confirmed their octahedral geometries. Magnetic investigation reported high-spin configurations for Mn(II), Co(II), and Ni(II) complexes, whereas Cu(II) exhibited a distorted octahedral arrangement with characteristic d–d transitions. In addition, the calculation of Density functional theory (DFT) provided more insight into the detailed structural and electronic properties of the new ligand and its complexes. Antimicrobial compounds were evaluated against Escherichia coli, Staphylococcus aureus, and Candida albicans through the agar well diffusion method. The reported results revealed that Cobalt complexes showed antimicrobial activity followed by Copper (Cu), Nickel (Ni) and Manganese(Mn) complexes, respectively, due to an increase in Co-lipophilicity, which leads to improved diffusion through microbial cell membranes. The research findings confirmed that escitalopram-based mixed ligands coordinate with transition metals and could have significant biological applications. Full article

Density functional theory calculations are performed to examine the reactivity of the coordinatively unsaturated (NH₃)₄RhO²⁺, (NH₃)₄CoO²⁺, and (NH₃)₄FeO⁺ species with methane and methanol. The ground low-spin state of rhodium oxide provides ideal energetics for the efficient and selective conversion of methane to methanol. The small activation energy barriers for all three steps (H₃C-H activation, CH₃-OH recombination, oxygen reload) promise fast conversion, while the larger activation barrier for the C-H activation of methanol provides the means to kinetically hinder further oxidation to the thermodynamically more favorable formaldehyde. The key finding was that rhodium prefers the 2 + 2 (as opposed to radical) activation mechanism of methane. To maintain the “ideal” electronic structure observed for (NH₃)₄RhO²⁺, we first replaced rhodium with its first-row lower cost counterpart cobalt. The cobalt complex favors a quartet state, which prefers a radical mechanism leading to the formation of methyl radical. This undesired effect vanishes, switching from Co⁴⁺ to Fe³⁺. Possible explanations for the observed trends are provided in terms of electronic structure features of the three metals. The production of methanol from methane has been a topic of intense interest over the past decades and we believe that this work offers new insights for tackling this challenging problem. Full article

A series of cobalt(II) dicyanamide (dca⁻) coordination polymers with substituted pyrazines (pyz) and pyrimidines (pym) as auxiliary ligands have been synthesized and structurally characterized to investigate the influence of the type and substitution pattern of the auxiliary ligand on the dimensionality and topology of the resulting frameworks. As a result of our studies, 13 novel heteroleptic cobalt(II) dicyanamide coordination polymers were obtained, and their crystal structures were determined by single-crystal X-ray diffraction. Eight of the investigated compounds exhibit a single-chain structure composed of [Co(L_pyz/_pym)₂]²⁺ units bridged via double μ_1,5–dca ligands. In two complexes, neutral triple-chain topologies were observed, in which double μ_1,5– and single μ_1,3,5–dca bridges connect two crystallographically independent cobalt(II) ions, both being six-coordinate in tetragonally elongated octahedral environments. Two- and three-dimensional architectures were confirmed only in the case of Co(II) compounds with 2,6–Me₂pyz and 4-NH₂-pym co-ligand, respectively The cobalt(II) complexes described herein have also been compared with dicyanamide-based cobalt(II) systems incorporating pyrazine- and pyrimidine-like ligands. These structural relationships are of high significance for the rational design and synthesis of heteroleptic cobalt(II) dicyanamide systems. Full article

Sulfonamides represent a versatile class of biologically active compounds, best known for their antibacterial activity, but increasingly investigated for their potential in oncology. Free sulfonamides themselves display cytotoxic properties; however, coordination with metal ions often enhances both selectivity and potency, while also introducing new mechanisms of action. Although numerous studies have reported sulfonamide–metal complexes with anticancer activity, a systematic overview linking biological properties to the central metal atom has been lacking. This review summarizes current research on sulfonamide complexes with transition metals and selected main-group elements, focusing on their pharmacological potential as anticancer agents. The compounds discussed include complexes of titanium, chromium, manganese, rhenium, ruthenium, osmium, iridium, palladium, platinum, copper, silver, gold, iron, cobalt, nickel, uranium, calcium, magnesium and bismuth. For each group, representative structures are presented along with cytotoxicity data against cancer cell lines, comparisons with reference drugs such as for example cisplatin, and where relevant, studies on carbonic anhydrase inhibition. The survey of available data demonstrates that many sulfonamide–metal complexes show cytotoxic activity comparable to or greater than existing chemotherapeutic agents, while in some cases exhibiting reduced toxicity toward non-cancerous cells. These findings highlight the promise of sulfonamide–metal complexes as a fertile area for anticancer drug development and provide a framework for future design strategies. This review covers the research on anti-cancer activity of sulfonamide complexes during the years 2007–2025. Full article

The ability of earth-abundant metals to serve as catalysts for the oxygen reduction reaction is of increasing importance given the prominence of this reaction in several emerging technologies. It is now recognized that both the primary and secondary coordination environments of these catalysts can be modulated to optimize their performance. In this present work, we describe two Co^II complexes [Co^II(PaPy₂Q)](OTf) (1) and [Co^II(PaPy₂N)](OTf) (2) that catalyze chemical and electrochemical dioxygen reduction. Both 1 and 2 contain Co^II centers in a N₅⁻ coordination environment, but 2 has a naphthyridine group that places a nitrogen atom in the secondary coordination sphere. Solid-state X-ray crystallography and solution-state spectroscopic measurements reveal that, apart from this second-sphere nitrogen in 2, complexes 1 and 2 have essentially identical properties. Despite these similarities, 2 performs the chemical reduction of dioxygen ~10-fold more rapidly than 1. In addition, 2 has an enhanced performance in the electrochemical reduction of dioxygen compared to 1. Both complexes yield a significant amount of H₂O₂ in the chemical reduction of dioxygen (>25%). The enhanced catalytic performance of 2 is attributed to the presence of the second-sphere nitrogen atom, which might enable the efficient protonation of cobalt–oxygen intermediates formed during turnover. Full article

The ZC4H2 gene is the site of congenital mutations linked to neurodevelopmental and musculoskeletal pathologies collectively termed ZARD (ZC4H2-Associated Rare Disorders). ZC4H2 consists of a coiled coil and a single novel zinc finger with four cysteines and two histidines, from which the protein obtains its name. Alpha Fold 3 confidently predicts a structure for the zinc finger but also for similarly sized random sequences, providing equivocal information on its folding status. We show using synthetic peptide fragments that the zinc finger of ZC4H2 is genuine and folds upon binding a zinc ion with picomolar affinity. NMR pH titration of histidines and UV–Vis of a cobalt complex of the peptide indicate its four cysteines coordinate zinc, while two histidines do not participate in binding. The experimental NMR structure of the zinc finger has a novel structural motif similar to RANBP2 zinc fingers, in which two orthogonal hairpins each contribute two cysteines to coordinate zinc. Most of the nine ZARD mutations that occur in the ZC4H2 zinc finger are likely to perturb this structure. While the ZC4H2 zinc finger shares the folding motif and cysteine-ligand spacing of the RANBP2 family, it is missing key substrate-binding residues. Unlike the NZF branch of the RANBP2 family, the ZC4H2 zinc finger does not bind ubiquitin. Since the ZC4H2 zinc finger occurs in a single copy, it is also unlikely to bind DNA. Based on sequence homology to the VAB-23 protein, the ZC4H2 zinc finger may bind RNA of a currently undetermined sequence or have alternative functions. Full article

The development of metallic coatings as Ni-Co alloys, with particular emphasis on their homogeneity, processability, and sustainability, is of the utmost significance. To address these challenges, the utilization of phenylsalicylimines (PSIs) as additives within deep eutectic solvents (DES) was investigated, assessing their influence on the electrodeposition process of these metals at an intermediate temperature of 60 °C, while circumventing aqueous reaction conditions. The findings demonstrated that the incorporation of PSIs markedly enhances coating uniformity, resulting in an optimal cobalt content of 37% and an average thickness of 24 µm. Electrochemical evaluations revealed improvements in charge and mass transfer, thereby optimizing process efficiency. Moreover, computational studies confirmed that PSIs form stable complexes with Co (II), modulating the electrochemical characteristics of the system through the introduction of the diethylamino electron-donating group, which significantly stabilizes the coordinated forms with both components of the DES. Additionally, the coatings displayed exceptional corrosion resistance, with a rate of 0.781 µm per year, and achieved an optimal hardness of 38 N HRC, conforming to ASTM B994 standards. This research contributes to the development of electroplating bath designs for metallic coating deposition and lays the groundwork for the advancement of sophisticated technologies in functional coatings that augment corrosion resistance and mechanical properties. Full article

In this study, 3-chlorothiophene-2-carboxylic acid (HL) was used as a main ligand to successfully synthesize four novel complexes: [Cu(L)₂(Py)₂(OH₂)₂] (1), [Co(L)₂(Py)₂(OH₂)₂] (2) (Py = pyridine), [{Ni(L)₂(OH₂)₄}₂{Ni(L)(OH₂)₅}]L•5H₂O (3), and [{Co(L)₂(OH₂)₄}₂{Co(L)(OH₂)₅}]L•5H₂O (4). All four compounds were identified by elemental analysis and ESI mass spectrometry, and subsequently characterized by IR spectroscopy, UV-visible diffuse reflectance spectroscopy, electron paramagnetic resonance spectroscopy, thermogravimetric analysis, single-crystal X-ray crystallography, and cyclic voltammetry. X-ray analyses revealed that complexes 1 and 2 exhibit a centrosymmetric pseudo-octahedral coordination geometry; the copper (II) and cobalt (II) metal ions, respectively, are located at the crystallographic center of inversion. The coordination sphere of the copper (II) complex is axially elongated in accordance with the Jahn–Teller effect. Intriguingly, for charge neutrality, compounds 3 and 4 crystallized as three independent mononuclear octahedrally coordinated metal centers, which are two $\left[\mathrm{M}{\mathrm{L}}_2{\left({\mathrm{O}\mathrm{H}}_2\right)}_4\right]$ complex molecules and one ${\left[\mathrm{M}\mathrm{L}{\left({\mathrm{O}\mathrm{H}}_2\right)}_5\right]}^{+}$ complex cation (M = ${\mathrm{N}\mathrm{i}}^{\mathrm{I}\mathrm{I}}$ and ${\mathrm{C}\mathrm{o}}^{\mathrm{I}\mathrm{I}}$, respectively), with the ligand anion ${\mathrm{L}}^{-}$ serving as the counter ion. The anticancer activities of these complexes were systematically assessed on human leukemia K562 cells, lung cancer A549 cells, liver cancer HepG2 cells, breast cancer MDA-MB-231 cells, and colon cancer SW480 cells. Among them, complex 4 shows significant inhibitory effects on leukemia K562 cells and colon cancer SW480 cells. Full article

Polyphenolic compounds, such as flavonoids, possess important structural and physico-chemical characteristics that in combination with their biological properties render them an important class of natural compounds with medicinal prospects. Chrysin is a well-known flavone with antioxidant activity and a multitude of other beneficial properties. The potential of flavonoids to coordinate with metal ions leads to derivatives with enhanced biological profile. Within this framework, four novel heteroleptic complexes of cobalt and nickel with chrysin and the aromatic bidentate chelating agents 2,2′-bipyridine and 1,10-phenanthroline were synthesized, as well as physico-chemically and structurally characterized. The in vitro antioxidant efficiency of the synthesized complexes was examined via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. All complexes showed notable radical scavenging capacity comparable to that of ascorbic acid, providing the incentive for further investigation of their therapeutic potential. Full article

This work explores the effect of geometry and the presence of a site available for carbon dioxide coordination in molecular catalysis of CO₂ reduction for cobalt complexes using electrochemical and spectroelectrochemical studies. The octahedral complexes [Co^II(bztpen)Br]PF₆ and [Co^II(bpy)₃](BF₄)₂, along with the trigonal bipyramidal complex [Co^II(TPA)Cl]Cl, were selected for this study (where bztepen = N-benzyl-N,N′,N′-tris-(pyridine-2-ylmethyl)-ethylenediamine), TPA = tris (2-pyridimethyl)-amine, and bpy = 2′-2′- pyridine). DFT calculations were performed to predict the geometries of the complexes and to propose the sites at which electron transfer occurs. Among the studied compounds, [Co^II(bpy)₃(BF₄)₂] exhibited the highest catalytic rate constant for CO₂ reduction (k = 1.22 × 10² M⁻¹·s⁻¹) compared to [Co^II(bztpen)Br]PF₆ (k = 8.93 × 10¹ M⁻¹·s⁻¹). The trigonal bipyramidal complex [Co^II(TPA)Cl]Cl presented the lowest catalytic rate constant for CO₂ reduction (k = 1.47 × 10¹ M⁻¹·s⁻¹). UV-Vis spectroelectrochemical studies and DFT calculations suggested the formation of [Co^I(bztpen)(CO)]⁺ and [Co^I(tpa)(CO)]⁺ species, which are associated with catalyst deactivation and may account for the lower performance of CO₂ reduction. Full article