Simple Metal Complexes Research Articles

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High‐energy relatives of benzene have captured the imagination of chemists, especially those with cumulative double bonds which feature strained ring structure and lack any aromaticity stabilization. The integration of transition metals and Group 14 elements into six‐membered cycloallene rings has been achieved by a [5+1]‐cycloaddition of diethynylsilane or diethynylgermane with simple transition metal complexes. Experimental and computational studies demonstrate the stability of these unprecedent cycloallenes, i.e. metalla‐isosilabenzenes and metalla‐isogermabenzenes, may root in the decreasing strain on the cumulative double bonds. More details are discussed in the article by Zhang et al. on page 1121—1127.image

Heavier Group 14 Congeners of Metalla‐isobenzenes: Access to Metalla‐isosilabenzene and Metalla‐isogermabenzene by One‐Pot Reactions

Comprehensive SummaryMetalla‐isosilabenzenes and metalla‐isogermabenzenes have been successfully synthesized by the formal [5+1]‐cycloaddition of diethynylsilane or diethynylgermane with simple metal complexes. This is the first example of a heavier Group 14 metalla‐isobenzene isomer bearing a cumulative double bond motif within a metallacycle. These novel complexes were fully characterized by NMR spectroscopy and single‐crystal X‐ray diffraction analysis. The stabilization of the cyclic metal‐vinylidene complexes has been analyzed using density functional theory (DFT) calculations. When the metalla‐isosilabenzenes bearing Si—H bond were treated with the trityl salt as a hydride scavenger, the formation of silylium cation was observed spectroscopically. Both of metalla‐isosilabenzenes and metalla‐isogermabenzenes can readily undergo migratory insertion reactions to furnish siloles or germoles.

Simple Trivalent Cobalt Complex-Mediated Copolymerization of Epoxides with Isocyanate: Combining High Activity and Selectivity

Controlled ring-opening copolymerization involving epoxides represents a valuable strategy for the synthesis of oxygenated polymers with unique biodegradability and biocompatibility. In this study, simple trivalent metal complexes, salenM(III)X (salen = N,N′-bis(salicylidine) diamine derivatives, M = Al, Cr, and Co), are employed for copolymerizing p-tosyl isocyanate (TSI) with epoxides, generating perfectly alternating polyurethanes with various structures and tunable properties. The trivalent cobalt acetate complex of N,N′-bis(salicylidine)-o-phenylenediamine bearing 3- and 3′-, 5- and 5′-tert-butyl groups exhibited the highest activity of up to 41,400 h–1 under mild conditions. This single-site catalyst also showed excellent activity and selectivity for copolymer formation even at an extremely low loading of 0.002 mol % without any cocatalyst activator and operated efficiently for various terminal epoxides, affording completely alternating polyurethanes with high molecular weights and narrow polydispersities. Also, this catalyst was tolerant of large quantities of chain transfer agents, thereby allowing control of the molecular weight. Notably, the ring opening of terminal epoxides predominantly occurring at the methylene C–O bond resulted in the formation of stereoregular polyurethanes with more than 96% head-to-tail content.

The new salt of 2-amino-3-methylpyridine with dipicolinic acid and its metal complexes: Synthesis, characterization and antimicrobial activity studies

A new proton transfer salt (3) synthesized from 2-amino-3-methyl pyridine with dipicolinic acid and its Fe(III) (4), Co(II) (5), Ni(II) and two Cu(II) (7 and 8) complexes were synthesized and characterized by NMR (1H and 13C), AAS, FT-IR, magnetic measurement, molar conductivity and UV. X–ray crystallography was performed to illuminate the structure of compounds 6 and 8. Additionally, metal salts (9–12), free compounds (1 and 2), simple metal complexes (13–20) of compounds 1 and 2 and synthesized compounds (3–8) have been assayed for their antimicrobial activities against Escherichia coli (ATCC 25,922) (Gram negative), Enterococcus faecalis (ATCC 29212) (Gram positive), Staphylococcus aureus (ATCC 29213) (Gram positive), Candida parapisilosis (ATCC 22019) (yeast), Candida albicans (ATCC 14053) (yeast) and Candida krusei (ATCC 6258) (yeast). Results of analyses were compared with Cefepime, Vancomycin and Levofloxacin (standard antibacterial agents) and Fluconazole (standard antifungal agents). Compounds with the best activity are 1, 3, 11, 16 and 17 (62.50) for E. Coli, 1, 11, 13 and 17 (31.25) for S. aureus, 11, 17 and 18 (31.25) for E. faecalis, 1, 3, 16 and 17 (31.25) for C. parapsilosis, 1 (15.60) for C. albicans and 1, 17, 18 and 20 (31.25) for C. krusei. Against all bacteria and yeasts, compound 17 had the highest activity (32.25) (except for C. albicans).

Syntheses, Polymorphic Transformations, and Functions of Ionic Crystals Based on Mononuclear Bismuth(III) Complexes and Polyoxometalates

AbstractThe controlled assembly of molecules, ions, and ligands as building blocks based on crystal engineering leads to various functional crystalline solids. In particular, polyoxometalates (POMs), which are anionic metal oxide clusters, have been a popular motif in crystal engineering. To revisit simple mononuclear metal complexes as counter cations of POMs, seven ionic crystals based on Keggin‐ or Dawson‐type POMs with mononuclear bismuth(III) complexes as counter cations were synthesized. The bismuth(III) center exhibited triangular dodecahedron, square antiprism, or pseudo‐cubic eight‐coordination geometries, with dimethyl sulfoxide or N,N‐dimethylformamide as ligands. The ionic crystals showed polymorphic transformation depending on the synthetic or recrystallization conditions. As a method for exploring functionality, proton conductivities of the ionic crystals were measured under humidified conditions. The ionic crystals with high porosity, tertiary amine moieties, or coordination water exhibited high proton conductivities, and large activation energies indicate that protons are transferred mainly with water molecules via the vehicle mechanism.

Spectroscopic and diffraction studies of polycrystalline copper sulfate pentahydrate at shocked conditions

As per the literature reports available so far, there are numerous experiments that have been conducted and demonstrated on the crystallographic phase stability of a variety of materials such as metals, inorganic and organic materials by the impact of the shock waves. In the present course of work, we have selected one of the simple metal complex hydrate materials of copper sulfate pentahydrate (CuSO4·5H2O) for shock wave recovery experiment so as to examine the phase stability and shock wave induced dehydration process since it has a high possibility of undergoing phase transition with the sequence of 5H2O/3H2O/H2O. The molecular and crystallographic phase details have been examined by Raman spectroscopy and powder X-ray diffractometry (PXRD). Surprisingly, as per the observed spectroscopic and diffraction studies, the title material has not undergone any phase transition.

Interpretation of multiple solutions in fully iterative GF2 and GW schemes using local analysis of two-particle density matrices.

Due to the presence of non-linear equations, iterative Green's function methods can result in multiple different solutions even for simple molecular systems. In contrast to the wave-function methods, a detailed and careful analysis of such molecular solutions was not performed before. In this work, we use two-particle density matrices to investigate local spin and charge correlators that quantify the charge resonance and covalent characters of these solutions. When applied within the unrestricted orbital set, spin correlators elucidate the broken symmetry of the solutions, containing necessary information for building effective magnetic Hamiltonians. Based on GW and GF2 calculations of simple molecules and transition metal complexes, we construct Heisenberg Hamiltonians, four-spin-four-center corrections, and biquadratic spin-spin interactions. These Hamiltonian parameterizations are compared to previous wave-function calculations.

Bis (Diamines) Cu and Zn Complexes of Flurbiprofen as Potential Cholinesterase Inhibitors: In Vitro Studies and Docking Simulations

Alzheimer’s disease (AD) causes dementia and continuous damage to brain cells. Cholinesterase inhibitors can alleviate the condition by increasing communication between the nerve cells and reducing the risk of dementia. In an effort to treat Alzheimer’s disease, we synthesized flurbiprofen-based diamines (1,2 diaminoethane and 1,3 diaminopropane) Zn(II), Cu(II) metal complexes and characterized them by single-crystal X-ray analysis, NMR, (FT)-IR, UV-Vis, magnetic susceptibility, elemental analysis and conductivities measurements. Synthesized diamine metal complexes appeared in ionic forms and have distorted octahedral geometry based on conductivity studies, magnetic susceptibility and electronic studies. Single crystal X-ray diffraction analysis confirmed (2b) Cu(H2O)2(L1)2(L2)2 complex formation. Moreover, we tested all synthesized metal complexes against the cholinesterase enzyme that showed higher inhibition potential. In general, copper metal complexes showed higher inhibitory activities than simple metal complexes with flurbiprofen. These synthesized metal complexes may derive more effective and safe inhibitors for cholinesterases.

Design and Engineering of Metal Catalysts for Bio-orthogonal Catalysis in Living Systems.

In the past two decades, bio-orthogonal transformations mediated by biocompatible metal catalysts in living systems have shown enormous potential in both synthetic biology and medicinal chemistry. These metal-mediated bio-orthogonal reactions, many of which could not be accomplished by natural enzymes, have created more possibilities in organic chemistry and biological sciences. Despite all of the challenges for making those abiotic catalysts work in complicated biological environments, many catalytic systems working in living systems have been reported, mediating different transformations such as uncaging of fluorescent probes, pro-drug activation, glycan or protein activation, labeling of proteins or cell surfaces, and in situ drug synthesis. This review categorizes and summarizes the recent development of synthetic metal catalysts for bio-orthogonal reactions in living systems within two decades. Ranging from simple metal complexes and macromolecular-scaffold-based catalytic systems to heterogeneous nanomaterial-based systems, we show those catalysts of diverse nature and highlight the strategies for their design and engineering. We analyze and describe the structure-property relationship of those biocompatible metal catalysts and show the importance of structural diversification and optimization for their potential applications. A brief overview of metal-mediated bio-orthogonal reactions for biological applications is also given, and the challenges and opportunities of this field are discussed from a long-term perspective.

Studying the reactivity of “old” Cu(II) complexes for “novel” anticancer purposes

Reactive oxygen species (ROS) formation appears as one of the most promising pathways to induce cell death. The interesting Cu(II)/Cu(I) redox pair has been reported to biologically generate ROS and induce cell damage. Simple metal complexes, such as cisplatin, sometimes offer even better properties than others highly accurately synthesized, which imply considerable time and economical efforts. This work relies on the synthesis and characterisation of four existing Cu(II) complexes bearing N-donor ligands, previously used for a totally different intend, but tested now for anticancer purposes. Furthermore, a relationship between their coordinating features, i.e. their redox behaviour, with their biological activity have been inferred to further understand the medicinal role of the Cu(II)/Cu(I) redox pair. Cytotoxicity studies and interactions towards DNA have been assessed, studying both covalent and non-covalent modes of binding via mass spectrometry (MS), UV–Vis and fluorescence, evaluating the cleaving properties of the assayed compounds, as well as their capacity to generate ROS inside the cells. The role of the ligand for one of the complexes has been evaluated by a computational approach. The idea of using “old” complexes for “novel” anticancer purposes can offer promising results in the future, being a simple but interesting approach to study, as we demonstrate here for most of the complexes analysed, showing a non-expected “new” and beneficial role.

Tris-diamine-derived transition metal complexes of flurbiprofen as cholinesterase inhibitors

Purpose: To synthesize novel tris-diamine-derived transition metal complexes of flurbiprofen M(C2H8N2)3 (fp)2 and M(C3H10N2)3 (fp)2, and to evaluate their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities.Method: Tris-diamine-derived transition metal complexes of Co(II), Ni(II), and Mn(II) were synthesized and characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, elemental analysis, magnetic susceptibility, conductivity measurement and single crystal x-ray analysis. The synthesized complexes were also evaluated for their AChE and BChE inhibitory activities.Results: Based on magnetic susceptibility and electronic studies, the synthesized complexes possessed distorted octahedral geometry. Conductance measurements indicated that diamine-derived metal complexes of flurbiprofen were electrolytes, whereas, simple metal complexes of flurbiprofen were non-electrolytes. The structure of Ni (C2H8N2)3 (fp)2 was also confirmed by single crystal x-ray analysis. The synthesized metal complexes exhibited moderate-to-very good inhibition of AChE and BChE. In vitro assays revealed that Ni complexes were most active, with the least half-maximal inhibitory concentration (IC50) values against AChE and BChE, compared to Co and Mn complexes. Furthermore, 1, 2-diaminoethane-derived complexes were more potent, with lower IC50 values against both AChE and BChE, compared to 1,3-diaminopropane-derived complexes. Among the complexes, 4a and 5a revealed significant cholinesterase inhibitory activities relative to the standard drug, galantamine.Conclusion: All the synthesized metal complexes are active against AChE and BChE, but only 4a and 5a are more active than the standard drug, galantamine, indicating their potential for drug development.Keywords: Flurbiprofen, Cholinesterase, Diamines, Galantamine, Metal complexes, Cholinesterase inhibition

CATALYSTS OF OXIDATION REACTION OF BUTENE-1 TO METHYLETHYLKETONE

The available and simple metal complex systems of catalytic oxidation of unsaturated hydrocarbons were developed. It is shown that these systems catalyze the selective liquid-phase oxidation of butene-1 to methyl ethyl ketone by molecular oxygen at low temperature. The best results were revealed using Cu(I)Cl monovalent chloride. The catalyst for the production of methylethylketone is a binary system containing complexes of copper and palladium chloride at a molar ratio of 2:1. Hexamethylphosphoramide is used as the ligand and palladium chloride complex as an additional complex contains benzonitrile. A combined catalyst has been offered. It allows to carry out the oxidation reaction of butene to methyl ethyl ketone under mild conditions (low temperature, atmospheric pressure) with high selectivity and yield of the desired product. The proposed binary system is able to coordinate molecular oxygen and butene-1, and thus it becomes possible to conduct the oxidation reaction not directly between butene-1 and O2, and using a specific complex catalyst system allowing them to react with each other in an activated coordinated state. Absorption properties of catalysts synthesized on the bases of transition metals have been studied and activation of molecular oxygen and butane-1 has been determined. As a result of interaction of coordinated oxygen and butane-1 it is possible to carry out oxidation reaction to methylethylketone in mild condition. The specific feature of the offered binary catalyst is irreversible absorption of molecular oxygen. Mild conditions of the reaction proceeding decreases considerably amount of by-products and simplify obtaining and separation of the main product-methylethylketone. Due to the fact that the absorption of O2 is irreversible and it is possible to easily remove the excess amount of O2 after the formation of the oxygen complex. The developed method has the advantage from the point of view of safety.Forcitation:Agaguseynova M.M., Amanullayeva G.I., Bayramova Z.E. Catalysts of oxidation reaction of butene-1 to methylethylketone. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 53-57

Cu2ZnSnS4 and Cu2ZnSn(S1−xSex)4 nanocrystals: room-temperature synthesis and efficient photoelectrochemical water splitting

CZTS and CZTSSe nanocrystals have been synthesized by a simple metal complex solution mixing (Metcomix) process at room temperature and employed as efficient photoanodes for photoelectrochemical water splitting.

Metal‐Containing Pharmacophores in Molecularly Targeted Anticancer Therapies and Diagnostics

Molecularly targeted therapeutic agents make up an important class of oncology drugs that are used either alone, or in combination with classical cytotoxic agents, to combat many solid tumors and hematological cancers. Their targets in cancer cells are proteins that are encoded by oncogenes, which regulate cell growth, survival, and proliferation. These include a number of signal‐transducing and angiogenesis‐related kinases, hormone receptors, and certain cell‐surface antigens. Targeting of cancer cells harboring oncogenic molecular targets with precision medicines, while sparing the vast majority of normal healthy cells, has led to promising new treatments for cancer patients. Molecularly targeted therapeutic agents promise higher efficacy and weaker side effects than the traditional cytotoxic chemotherapies. Simple metal complexes and metal–organic hybrid agents have been the subjects of investigation for many years since the success of cisplatin in treating genitourinary cancers, but their applications in targeted therapies remain underexplored. In this review we highlight the development of metal‐based targeted cancer therapeutic agents with unique structures and functions. These strategies provide exciting opportunities for discovering new therapeutic and diagnostic agents for clinical uses.

Bovine Serum Albumin Metal Complexes for Mimic of SOD

Superoxide anion radical (O\(_{2}^{\bullet -}\)) is a noxious reactive oxygen species (ROS). Transition metal ion complexes have been generally used as antioxidants to eliminate ROS. In this work, a neoteric water-soluble biopolymer metal complex (BSA-M) was prepared by conjugating the soluble biopolymer bovine serum albumin (BSA) with three transition metal ions (M, M =Cu, Co, Mn). The binding mode and ratio of metal ions bound to albumin were investigated. The BSA-M complexes were characterized by UV-Vis, circular dichroism (CD) spectra and polyacrylamide gel electrophoresis (PAGE). BSA served as polymer scaffold and the metal complex functioned as the catalytic active center. The results demonstrated that the structure of BSA remained unchanged when the binding ratio of transition metal ion complex to BSA was 5:1. Furthermore, the scavenging superoxide anion free radical (O\(_{2}^{\bullet -}\)) activity of biopolymer-metal complexes were determined by nitroblue tetrazolium light reduction assay method. The antioxidant capacity of BSA-M has markedly increased. The conjugated BSA-M (M=Cu, Mn) showed preeminent scavenging activity for O\(_{2}^{\bullet -}\), and the EC50 value of the BSA-Cu was 0.038 ±0.0013 μ mol⋅L −1, which is comparable to EC50 value (0.041±0.001 μ mol⋅L −1) of the natural superoxide dismutase (SOD), the analog quantity reached 107%. As a consequence, it can be considered as a bio-functional mimic of enzyme SOD and has a promising application prospect in antioxidant drug field. A simple biopolymer metal complex (BSA-M) was formed via BSA binding with transition metal ions, in which BSA served as scaffold and the metal ions as the catalytic active centers. BSA-Cu showed remarkable capacity for scavenging of O2⦁−.

Synthesis and characterization of a novel proton salt of 2-amino-6-nitrobenzothiazole with 2,6-pyridinedicarboxylic acid and its metal complexes and their antimicrobial and antifungal activity studies

A novel proton transfer compound, (O2NHABT)+(HDPC)−.0.4EtOH (1), obtained from 2-amino-6-nitrobenzothiazole (O2NABT) and 2,6-pyridinedicarboxylic acid (H2DPC), and its Fe(III), Co(II), Ni(II) and Cu(II) complexes (2–5) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to complexes 3–5. While complexes 3 and 4 have distorted octahedral conformations, complex 5 exhibits a distorted square pyramidal structure. The structure of 2 might be proposed as octahedral according to spectral and analytical results. Furthermore, parent compounds, O2NABT and H2DPC, simple metal complexes of H2DPC, and the synthesised compounds (1–5) were screened for their antibacterial and antifungal activities against Staphylococcus aureus (ATCC 29213) (Gram positive), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC 29212) (Gram negative) and Candida krusei (ATCC 6258), Candida parapisilosis(ATCC 22019) (yeast). The results were compared with the control compounds, Vancomycin, Cefepime, Levofloxasin as antibacterial, and Flucanozole as antifungal agents.

Magneto-Structural Correlations in a Series of Pseudotetrahedral [Co(II)(XR)4](2-) Single Molecule Magnets: An ab Initio Ligand Field Study.

Over the past several decades, tremendous efforts have been invested in finding molecules that display slow relaxation of magnetization and hence act as single-molecule magnets (SMMs). While initial research was strongly focused on polynuclear transition metal complexes, it has become increasingly evident that SMM behavior can also be displayed in relatively simple mononuclear transition metal complexes. One of the first examples of a mononuclear SMM that shows a slow relaxation of the magnetization in the absence of an external magnetic field is the cobalt(II) tetra-thiolate [Co(SPh)4](2-). Fascinatingly, substitution of the donor ligand atom by oxygen or selenium dramatically changes zero-field splitting (ZFS) and relaxation time. Clearly, these large variations call for an in-depth electronic structure investigation in order to develop a qualitative understanding of the observed phenomena. In this work, we present a systematic theoretical study of a whole series of complexes (PPh4)2[Co(XPh)4] (X = O, S, Se) using multireference ab initio methods. To this end, we employ the recently proposed ab initio ligand field theory, which allows us to translate the ab initio results into the framework of ligand field theory. Magneto-structural correlations are then developed that take into account the nature of metal-ligand covalent bonding, ligand spin-orbit coupling, and geometric distortions away from pure tetrahedral symmetry. The absolute value of zero-field splitting increases when the ligand field strength decreases across the series from O to Te. The zero-field splitting of the ground state of the hypothetical [Co(TePh)4](2-) complex is computed to be about twice as large as for the well-known (PPh4)2[Co(SPh)4] compound. It is shown that due to the π-anisotropy of the ligand donor atoms (S, Se) magneto-structural correlations in [Co(OPh)4](2-) complex differ from [Co(S/SePh)4](2-). In the case of almost isotropic OPh ligand, only variations in the first coordination sphere affect magnetic properties, but in the case of S/SePh ligand, variations in the first and second coordination sphere become equally important for magnetic properties.

Stepwise Conversion of a Platinum Dimethyl Complex to a Perfluorometallacyclobutane Derivative

In this report, we have demonstrated proof-in-principle that simple dimethyl metal complexes could be used to generate perfluorometallacyclobutane derivatives. With the new methodology, we have more than doubled the number of known perfluorometallacyclobutanes in the literature. We have also structurally characterized three platinum perfluorometallacyclobutanes and have described a unique transformation whereby one [Pt(C3F6)] functionality is converted to [Pt(C3F4O2)]. The new methodology to prepare perfluorometallacyclobutanes also avoids the use of tetrafluoroethylene, which is becoming increasingly difficult to purchase due to the explosion hazards associated with its use.

Catalytic generation of hydroxyl radicals by dioxygen-mediated oxidation of p-aminophenol by simple cobalt(ii) ions in bicarbonate aqueous solution for use in Acid Orange 7 decolorization

Dioxygen from air is the cleanest and the most abundant oxidative agent; it is of great significance to activate dioxygen to reactive oxygen species for environmental pollutant transformation and degradation. In this work, the simple cobalt(II) ion was found to exhibit high efficiency for p-aminophenol oxidation in bicarbonate aqueous solution with dioxygen as the oxidant at room temperature; simultaneously, the azo dye, Acid Orange 7, can be decolorized by the system. The formed reactive species was carefully studied by electron spin resonance and spin-trapping technologies and radical scavenging measurements. The metal-bound hydroxyl radical, which originated from a Fenton-like reaction between the Co2+–HCO3− complex and the intermediate of H2O2, was suggested as the main reactive species. This study can provide new insight into the mechanism of the molecular oxygen activation by simple metal complexes and their application to the removal or transformation of pollutants under mild reaction conditions.

Synthesis and characterization of complexes of a novel proton transfer salt and their inhibition studies on carbonic anhydrase isoenzymes

A novel proton transfer compound (HClABT)+(HDPC.H2DPC)− (1) and its Fe(III), Co(II), Ni(II) and two different Cu(II) complexes (2–6) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to all complexes. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human hCA I and hCA II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. The comparison of the inhibition studies of 1–6 to parent compounds, ClABT and H2DPC, indicates that 1–6 have superior inhibitory effects. The inhibition effects of 2–6 are also compared to the inhibitory properties of the simple metal complexes of ClABT and H2DPC, revealing an improved transfection profile. Data have been analysed by using a one-way analysis of variance for multiple comparisons.