Metal Coordination Compounds Research Articles

Recent Insights into Magneto-Structural Properties of Co(II) Dicyanamide Coordination Compounds

In recent decades, the chemistry of transition metal coordination compounds has undergone continuous development at both scientific and application levels. The diversity of metal(II) complexes, along with their structural features and physicochemical properties, makes them attractive for a wide range of applications. The dicyanamide ion (N(CN)2) has the ability to form various transition metal compounds characterized by different architectures and topologies. The interaction of π-electrons from the nitrile groups with the π-system of the central nitrogen may enable electron delocalization, potentially facilitating electron transfer between the metal centers through the bridging dicyanamide (dca) ligand. This review focuses on dca–Co(II) compounds and, after a brief introduction, the structural aspects and magnetic properties are analyzed in detail.

Coordination Compounds of Alkali and Rare Earth Metals Based on Centrosymmetric Chlorine-Substituted Bis-Mercaptooxazole. Synthesis, Structure, and Luminescence

New coordination polymers were synthesized. A ditopic centrosymmetric organic ligand containing oxazole heterocycles, 4,8-dichlorobenzo[1,2d:4,5d´]bis(oxazole)-2,6(3H,7H)-dithione (H2L), was prepared and structurally characterized. It was shown that deprotonated H2L forms non-luminescent binuclear molecular complexes Li2L(THF)6 (I) and Na2L(DME)4 (II) with alkali metals, while complexes of H2L with lanthanides are ionic compounds [Ln(DMSO)8][L]1.5 (Ln = Nd (III), Yb (IV)) exhibiting moderate metalcentered emission in the near-infrared (IR) range, despite the absence of coordination of the ligand L to lanthanide ions. The molecular structures of H2L·2DMSO and I–III were established by X-ray diffraction (CCDC no. 2320461 (H2L·2DMSO), 2320462 (I), 2320463 (II), 2320464 (III)).

Metal Coordination Compounds for Organic Redox Flow Batteries

AbstractAlong with the continuous optimization of the energy structure, more and more electricity come from intermittent renewable energy sources such as wind and solar energy. Redox flow batteries (RFBs) have the advantage that energy and power can be regulated independently, so they are widely used in large‐scale energy storage. Redox active materials are the important components of RFBs, which determine the performance of the battery and the cost of energy storage. Some metal coordination compounds (MCCs) and their derivatives have been considered redox active materials that can replace metal‐based redox flow batteries due to their properties such as tunability, high abundance and sustainability. MCCs can provide higher energy density because they are highly soluble both in the initial state and in any charged state during the battery cycling process. MCCs have also attracted a lot of attention from researchers because of their high economic value, low toxicity, and wide availability. This review provides an overview of the recent development of soluble metal coordination compounds, such as Ferrocene, and concludes with an in‐depth discussion of the prospects of metal coordination compounds for application in organic redox flow batteries.

Rare earth based photocatalysts for hydrogen peroxide production☆

Hydrogen peroxide (H2O2) is a versatile compound with widespread applications in various industries. In addition, it has attracted interest as a potential energy carrier due to its high energy density and ability to release oxygen upon decomposition. The development of photocatalytic technology has enabled sustainable production of H2O2. Various structural materials, including organic molecules, polymers, and metal coordination compounds, have been synthesized for investigating photocatalytic H2O2 production. Rare earth materials, in particular, are of interest due to their adjustable porosity and controllable metal active sites, making them valuable for research in this field. These materials have excellent photoelectric properties, making them promise for the photocatalytic synthesis of H2O2. Despite limited reports on systematic reviews of photocatalytic H2O2 production using rare earth materials, this study introduces the principles and advancements in this area. It reviews different methods of photocatalytic synthesis of H2O2, focusing on rare earth elements. Through comprehensive analysis and systematic studies in the existing literature, a deeper understanding of enhanced photocatalytic performance has been achieved. This research not only contributes to advancing fundamental knowledge but also provides a solid foundation for practical applications.

Energetic Coordination Compounds: Investigation of Aliphatic Ligands and Development of Prototype Detonators.

In this work, energetic coordination compounds (ECCs) of transition metals (Fe, Ni, Cu, Zn) containing aliphatic amines as ligands were synthesized: ethylenediamine; 1,3-diaminopropane; tris(2-aminoethyl)amine; tris(3-aminopropyl)amine. The compounds were investigated in terms of ignition/explosion temperature, friction and impact sensitivity. For selected compounds, structural characterisation was presented (IR-ATR spectroscopy, Raman spectroscopy) and their morphology was determined (SEM, powder XRD). They were also investigated by differential scanning calorimetry (DSC). In order to assess the potential application of selected ECCs in detonators, underwater explosion tests were carried out, determining energetic performance. The results achieved for detonators containing ECCs were compared with those for reference detonators (containing pentaerythritol tetranitrate, PETN), indicating their potential use as a "green" alternative to nitric acid esters.

Coordination Compounds of 3d Metals with 2,4-Dimethylpyrazolo[1,5-а]benzimidazole: Magnetic and Biological Properties

Coordination Compounds of 3d Metals with 2,4-Dimethylpyrazolo[1,5-а]benzimidazole: Magnetic and Biological Properties

Pre-Service Chemistry Teachers’ Preconceptions about Rare Earth Coordination Chemistry: Results from an Explorative Interview Study

This research aims to identify students' preconceptions about rare earth coordination chemistry. The method used in this research is exploratory interviews. This research involved 25 pre-service chemistry teacher at a university in West Java Province, Indonesia. The collected data was analyzed using qualitative content analysis. The research results showed that 60% of students were able to identify electronic waste as a source of valuable metals, but others did not know that there were rare earth metals contained in it. As many as 32% know ionic liquids as environmentally friendly solvents, but the majority of students do not understand the physicochemical properties of ionic liquids and the interactions between ionic liquids and rare earth metals. As many as 8% of students were able to explain the reaction to form rare earth metal coordination compounds correctly, while only 4% were able to explain the concept of luminescence in these compounds. These findings indicate the need for coordination chemistry course design that accommodates students' learning needs and links them to relevant environmental contexts to improve students' understanding and systems thinking skills.

Coordination Compounds of Alkali and Rare Earth Metals Based on Centrosymmetric Chlorine-Substituted Bismercaptooxazole. Synthesis, Structure, and Luminescence

Coordination Compounds of Alkali and Rare Earth Metals Based on Centrosymmetric Chlorine-Substituted Bismercaptooxazole. Synthesis, Structure, and Luminescence

Exploring the antioxidant activity of 1-(piperidin-1-yl) propane-1,2-dione 4-phenylthiosemicarbazone and 3d metal coordination compounds with this ligand

The new 1-(piperidin-1-yl)propane-1,2-dione 4-phenylthiosemicarbazone (HL) and its 7 coordination compounds [Cu(L)X] (X = Br- (I); Cl- (II); NO3 - (III); CH3COO- (IV); Cl2CHCOO- (V)), [Co(L)2]NO3 (VI), [Fe(L)2]NO3 (VII) have been synthesized and characterized by elemental analysis, FTIR, 1H, 13C NMR spectra and molar electric conductibility. For the obtained compounds it was studied the antioxidant activity towards ABTS•+ radical cation. Uncoordinated 4-phenylthiosemicarbazone HL is the most active one with IC50 14.1 μM. Its activity is higher than that of Trolox which is used in medicine as an antioxidant. Among all the synthesized coordination compounds, the iron(III) complex VII showed the greatest activity. The antioxidant activity of metal complexes is influenced by the anion and the nature of the central metal atom.

Does the Central Nitrogen Atom Make a Difference? A Comparison of Non‐Coordinating Pyridine and Benzene Spacers in Multitopic Ligands

AbstractIn metal coordination compounds of the divergent ligands 4,2′:6′,4“‐terpyridine and 3,2′:6′,3”‐terpyridine and their 4′‐functionalized derivatives, the central pyridine ring of the 4,2′:6′,4“‐terpyridine and 3,2′:6′,3”‐terpyridine domains is non‐coordinated. We present an overview of data from the Cambridge Structural Database to assess whether there are structural similarities between the coordination compounds of 4,2′:6′,4“‐tpy and 1,3‐di(pyridin‐4‐yl)benzene, and between 3,2′:6′,3”‐tpy and 1,3‐di(pyridin‐3‐yl)benzene. Based upon structurally characterized compounds, it emerges that the coordination chemistry of ligands including one or more 4,2′:6′,4“‐terpyridine or 3,2′:6′,3”‐terpyridine metal‐binding domains is more abundantly exemplified than that of corresponding ligands based upon 1,3‐di(pyridin‐4‐yl)benzene and 1,3‐di(pyridin‐3‐yl)benzene. We provide an overview of metallamacrocycles and cages, 1D‐coordination polymers and 2D‐ and 3D‐networks.

Synthesis, Spectral Characterization, Antibacterial and Anticancer Evaluation of Novel Isoniazid based Schiff Base Ligand derived Transition Metal Complexes

A novel isoniazid based Schiff base ligand was synthesized by the condensation of 5-acetyl-N-(adamantan-2-yl)thiophene-2-carboxamide (1 mmol) and isoniazid (1 mmol). Metal complexes were prepared by reacting the Schiff base with metal(II) chloride (M = Ni2+, Cu2+ and Co2+), formed the novel metal coordination compound. The synthesized ligand and metal complexes were characterized by 1H NMR, mass spectral, UV-visible, IR & EPR spectral studies, themogravimetric analysis, cyclic voltametry and were screened with both Gram-positive and Gram-negative bacterias to evaluate the antibacterial activity by disc diffusion method. The zone of inhibition of the antibacterial assay demonstrated that all the three metal(II) complexes are active against the four bacterias, showed increased activity with increase in concentration and is more active against S. aureas at all concentrations. The systhesized complexes were also evaluated for its anticancer activities, only Ni(II) and Co(II) complexes showed the moderate levels of cytotoxicity activity.

Coumarin-transition metal complexes with biological activity: current trends and perspectives.

Coumarin (2H-1-benzopyran-2-one) presents the fundamental structure of an enormous class of biologically active compounds of natural, semi-synthetic, and synthetic origin. Extensive efforts are continually being put into the research and development of coumarin derivatives with medicinal properties by the broad scientific community. Transition metal coordination compounds with potential biological activity are a "hot topic" in the modern search for novel drugs. Complexation with transition metals can enhance the physiological effect of a molecule, modify its safety profile, and even imbue it with novel attributes of interest in the fields of medicine and pharmacy. The present review aims to inform the reader of the latest developments in the search for coumarin transition metal complexes with biological activity, their potential applications, and structure-activity relationships, where such can be elucidated. Each section of the present review addresses a certain kind of biological activity (antiproliferative, antioxidant, antimicrobial, etc.), explores the most recent discoveries in the field, and, at the same time, tries to offer useful perspectives for potential future investigations.

Anticancer Metallocenes and Metal Complexes of Transition Elements from Groups 4 to 7.

With the progression in the field of bioinorganic chemistry, the role of transition metal complexes as the most widely used therapeutics is becoming a more and more attractive research area. The complexes of transition metals possess a great variety of attractive pharmacological properties, including anticancer, anti-inflammatory, antioxidant, anti-infective, etc., activities. Transition metal complexes have proven to be potential alternatives to biologically active organic compounds, especially as antitumor agents. The performance of metal coordination compounds in living systems is anticipated to differ generally from the action of non-metal-containing drugs and may offer unique diagnostic and/or therapeutic opportunities. In this review, the rapid development and application of metallocenes and metal complexes of elements from Groups 4 to 7 in cancer diagnostics and therapy have been summarized. Most of the heavy metals discussed in the current review are newly discovered metals. That is why the use of their metal-based compounds has attracted a lot of attention concerning their organometallic and coordination chemistry. All of this imposes more systematic studies on their biological activity, biocompatibility, and toxicity and presupposes further investigations.

Self-assembled hydrated copper coordination compounds as ionic conductors for room temperature solid-state batteries

As the core component of solid-state batteries, neither current inorganic solid-state electrolytes nor solid polymer electrolytes can simultaneously possess satisfactory ionic conductivity, electrode compatibility and processability. By incorporating efficient Li+ diffusion channels found in inorganic solid-state electrolytes and polar functional groups present in solid polymer electrolytes, it is conceivable to design inorganic-organic hybrid solid-state electrolytes to achieve true fusion and synergy in performance. Herein, we demonstrate that traditional metal coordination compounds can serve as exceptional Li+ ion conductors at room temperature through rational structural design. Specifically, we synthesize copper maleate hydrate nanoflakes via bottom-up self-assembly featuring highly-ordered 1D channels that are interconnected by Cu2+/Cu+ nodes and maleic acid ligands, alongside rich COO− groups and structural water within the channels. Benefiting from the combination of ion-hopping and coupling-dissociation mechanisms, Li+ ions can preferably transport through these channels rapidly. Thus, the Li+-implanted copper maleate hydrate solid-state electrolytes shows remarkable ionic conductivity (1.17 × 10−4 S cm−1 at room temperature), high Li+ transference number (0.77), and a 4.7 V-wide operating window. More impressively, Li+-implanted copper maleate hydrate solid-state electrolytes are demonstrated to have exceptional compatibility with both cathode and Li anode, enabling long-term stability of more than 800 cycles. This work brings new insight on exploring superior room-temperature ionic conductors based on metal coordination compounds.

Elevating the energetic capabilities of metal coordination compounds by incorporating nitrate anions.

In the realm of energetic materials research, there has been notable interest in energetic coordination compounds (ECCs) owing to their remarkable thermal stability and resistance to mechanical stimuli. This study successfully demonstrated the synthesis of an azole-based C-C bonded ECC1 under ambient conditions. A comprehensive characterization study, employing techniques such as IR, TGA-DSC, NMR and single-crystal X-ray diffraction analysis, was conducted. The bulk compound was investigated by PXRD analysis. In-depth exploration of its physicochemical and energetic performance revealed good detonation properties such as a detonation velocity (VOD) of 8553 m s-1 and a detonation pressure (DP) of 36.2 GPa, which surpass those of heat resistant explosives HNS and TATB. Due to its remarkable high melting and onset decomposition temperature (278/379 °C), it also outperforms the benchmark explosive HMX (279 °C) and the heat-resistant explosive HNS (318 °C) and shows a high impact sensitivity (IS) of 20 J and friction sensitivity (FS) of 360 N. The study also employed Hirshfeld surface and 2D fingerprint analysis to elucidate the close contact of atoms within the molecules. The combination of high detonation properties, thermal stability, and low sensitivity makes the synthesized ECC1 intriguing for further investigations and suggests its potential applications as a safe and high-energy-dense material.

Active Sites of Cobalt Phthalocyanine in Electrocatalytic CO2 Reduction to Methanol.

Many metal coordination compounds catalyze CO2 electroreduction to CO, but cobalt phthalocyanine hybridized with conductive carbon such as carbon nanotubes is currently the only one that can generate methanol. The underlying structure-reactivity correlation and reaction mechanism desperately demand elucidation. Here we report the first in situ X-ray absorption spectroscopy characterization, combined with ex situ spectroscopic and electrocatalytic measurements, to study CoPc-catalyzed CO2 reduction to methanol. Molecular dispersion of CoPc on CNT surfaces, as evidenced by the observed electronic interaction between the two, is crucial to fast electron transfer to the active sites and multi-electron CO2 reduction. CO, the key intermediate in the CO2 -to-methanol pathway, is found to be labile on the active site, which necessitates a high local concentration in the microenvironment to compete with CO2 for active sites and promote methanol production. A comparison of the electrocatalytic performance of structurally related porphyrins indicates that the bridging aza-N atoms of the Pc macrocycle are critical components of the CoPc active site that produces methanol. In situ X-ray absorption spectroscopy identifies the active site as Co(I) and supports an increasingly non-centrosymmetric Co coordination environment at negative applied potential, likely due to the formation of a Co-CO adduct during the catalysis.

Active Sites of Cobalt Phthalocyanine in Electrocatalytic CO2 Reduction to Methanol

AbstractMany metal coordination compounds catalyze CO2 electroreduction to CO, but cobalt phthalocyanine hybridized with conductive carbon such as carbon nanotubes is currently the only one that can generate methanol. The underlying structure–reactivity correlation and reaction mechanism desperately demand elucidation. Here we report the first in situ X‐ray absorption spectroscopy characterization, combined with ex situ spectroscopic and electrocatalytic measurements, to study CoPc‐catalyzed CO2 reduction to methanol. Molecular dispersion of CoPc on CNT surfaces, as evidenced by the observed electronic interaction between the two, is crucial to fast electron transfer to the active sites and multi‐electron CO2 reduction. CO, the key intermediate in the CO2‐to‐methanol pathway, is found to be labile on the active site, which necessitates a high local concentration in the microenvironment to compete with CO2 for active sites and promote methanol production. A comparison of the electrocatalytic performance of structurally related porphyrins indicates that the bridging aza‐N atoms of the Pc macrocycle are critical components of the CoPc active site that produces methanol. In situ X‐ray absorption spectroscopy identifies the active site as Co(I) and supports an increasingly non‐centrosymmetric Co coordination environment at negative applied potential, likely due to the formation of a Co−CO adduct during the catalysis.

Crown-hydroxylamines are pH-dependent chelating N,O-ligands with a potential for aerobic oxidation catalysis

Despite the rich coordination chemistry, hydroxylamines are rarely used as ligands for transition metal coordination compounds. This is partially because of the instability of these complexes that undergo decomposition, disproportionation and oxidation processes involving the hydroxylamine motif. Here, we design macrocyclic poly-N-hydroxylamines (crown-hydroxylamines) that form complexes containing a d-metal ion (Cu(II), Ni(II), Mn(II), and Zn(II)) coordinated by multiple (up to six) hydroxylamine fragments. The stability of these complexes is likely to be due to a macrocycle effect and strong intramolecular H-bonding interactions between the N−OH groups. Crown-hydroxylamine complexes exhibit interesting pH-dependent behavior where the efficiency of metal binding increases upon deprotonation of the hydroxylamine groups. Copper complexes exhibit catalytic activity in aerobic oxidation reactions under ambient conditions, whereas the corresponding complexes with macrocyclic polyamines show poor or no activity. Our results show that crown-hydroxylamines display anomalous structural features and chemical behavior with respect to both organic hydroxylamines and polyaza-crowns.

Functional pyrazolylpyridine ligands in the design of metal complexes with tunable properties

(1<i>H</i>-Pyrazolyl)pyridines are highly demanded ligands in coordination chemistry. Compounds of this class are analogues of 2,2'-bipyridine ligands. They possess a number of benefits such as ready availability and the ease of synthesis. They can function as bridging counter-ions because of deprotonation of the NH group. This review summarizes the general methods for the synthesis of pyrazole derivatives substituted with pyridine in position 1 or 3(5). The approaches to the preparation of (1<i>H</i>-pyrazolyl)pyridine ligands, arranged according to the type of coordination, are integrated and analyzed. The coordination compounds of various metals, including noble and coin metals, formed on the basis of these ligands, are described. It was shown that the structure of pyrazolylpyridine determines the photophysical and chemical properties of the metal complex. The results can be used to establish the functional ligand — structure of the complex — property relationships.<br> The bibliography includes 119 references.

Samarium- and Ytterbium-Grafted Periodic Mesoporous Silica for Carbon Dioxide Capture and Conversion.

Immobilized coordination compounds of Lewis acidic metals are powerful catalytic components of systems for the cycloaddition of CO2 to epoxides that do not require sophisticated coordination frameworks to harness the metal center and modulate its activity. Surface organometallic chemistry (SOMC) is a valuable methodology to prepare well-defined and site-isolated surface complexes and coordination compounds on metal oxides, with ligand environments easily adjustable to a targeted catalytic reaction. In this work, the SOMC methodology is applied to prepare SmII, YbII, and SmIII alkoxide surface complexes on periodic mesoporous (organo)silica of distinct pore symmetry/size for application in the CO2 cycloaddition reaction. The surface complexes are readily accessible by the grafting of the bis(trimethylsilyl)amide precursors LnII[N(SiMe3)2]2(THF)2 (Ln = Sm, Yb) and SmIII[N(SiMe3)2]3, followed by ligand exchange with alcohols (ethanol and neopentanol). The use of periodic mesoporous supports led to hybrid materials with relatively high surface areas and pore sizes, affording good performance in CO2 capture and in the cycloaddition of CO2 to epoxides under mild conditions (60-80 °C, 1-10 bar). In terms of catalytic performance, recyclability, and low amount of added nucleophile TBAX (X = Br, I), the most active materials prepared in this work compare well to a variety of previously reported SOMC-derived surface complexes and to other heterogeneous Lewis acids displaying more elaborate ligand environments.