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<figure class="table"><table><tbody><tr><td>Visible-light-driven photoreactions using metal complexes as catalysts are currently a research hotspot in terms of the development of environmentally friendly sustainable processes. To develop potential copper-based photocatalysts, a Mannich base ligand, namely, 2,4-dichloro-6-((4-(2-hydroxyethyl)piperazin-1-yl)methyl)phenol (H2L), has been synthesized and characterized. Two copper complexes [Cu (HL1)] (1) and [Cu (HL2)] (2) have been obtained from H2L, where the ligand undergoes an unprecedented transformation plausibly via oxidation of piperazine ring to ketone, subsequent oxidation of enol and nucleophilic attack of methanol followed by hydrolysis of amide bond, resulting piperazine ring cleavage. Under the irradiation of visible light, these catalysts can oxidize primary alcohols into corresponding aldehydes with very good conversion and high selectivity in the presence of molecular oxygen. The photocatalysts could be recovered almost quantitatively after completion of the catalytic cycle and recycled at least four times without much depreciation of catalytic activity. A plausible mechanistic pathway for alcohol oxidation has been explored through electrospray ionization mass spectrometry (ESI-MS) spectrometric, cyclic voltammetry, UV–vis, and computational study. © 2021 John Wiley &amp; Sons, Ltd.</td></tr></tbody></table></figure>

Applied Organometallic Chemistry

<p>Synthesis of Cu(II) complexes by N,O-donor ligand transformation and their catalytic role in visible-light-driven alcohol oxidation<br/> </p>

Ferrocenyl and ruthenocenyl derivatives of ebselen are found to be competitive inhibitors of mammalian TrxR, with IC50 of 4.2 ± 0.3 and 2.5 ± 0.3 µM, respectively. The inhibition of TrxR is selective over GR, and in the presence of excess GSH. They exhibit lower Km values than ebselen and the natural substrate, Trx. © 2021 Elsevier B.V.

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Journal of Organometallic Chemistry

Metallocenyl derivatives of ebselen are selective and competitive inhibitors of thioredoxin reductase

Four ruthenium(II)-arene complexes, viz. [Ru(p-cym)(2-ampy)Cl]PF6 1, [Ru(benzene)(2-ampy)Cl]SO3CF3 2, [Ru(p-cym)(2-ampy)PPh3](PF6)2 3 and [Ru(benzene)(2-ampy)PPh3](SO3CF3)2 4 [2-ampy = 2-aminomethyl pyridine] have been synthesized and characterized. Different analytical techniques have been utilized to characterize 1–4 and a DFT study was used to optimize the geometries and calculate the energies of the frontier molecular orbitals. An MTT assay revealed the potency of complexes 1–4 against MCF-7 (breast cancer) and Hela (cervical cancer) cell lines. The presence of the triphenyl phosphine ligand in complexes 3 and 4 makes the complexes more cytotoxic with respect to their chloro-analogues. The complexes are found to be specifically cytotoxic against cancerous cell lines only, as they were inactive against the normal HEK 293 cell line. An absorption and fluorescence titration study of complexes 1–4 showed significant interactions with DNA and proteins. Interestingly, all the complexes show potent catalytic activity for the hydrogen transfer of NADH and converted NADH to NAD+, which helps to induce the accumulation of intracellular reactive oxygen species (ROS) in MCF-7 cells. To analyze the morphological changes in the cells, the Hoechst staining method was applied to capture images of apoptotic cells through confocal microscopy. © 2021 Elsevier Ltd

Polyhedron

Modulation of catalytic and biomolecular binding properties of ruthenium(II)-arene complexes with the variation of coligands for selective toxicity against cancerous cells

Tetranuclear copper(ii) complexes are of paramount importance in structural biology, and they are potential materials for magnetism and catalysis. To develop such a system, a new 6-aminoazouracil ligand, 1,3-dimethyl-5-(o-phenolate-azo)-6-aminouracil (H2L, 1) with a NuNaO (Nu, uracil-N and Na, azo-N) chromophore was synthesized and used to generate a noble discrete doubly opened Cu4O4cubane-like cluster ([CuL]4·2H2O,2.2H2O) for studying magnetism. The coordination environment of Cu(ii) is distorted square planar linked through phenolate-μ2-O bridges. The ligand crystallizes in the monoclinic space groupP121/c1 and the complex is in the tetragonalI41/aspace group with anS4symmetry. The ligand has two dissociable hydrogen atoms in the solution with pK14.91 (hydrazone proton) and pK29.68 (phenolic proton). In the solid state, the ligand exhibits displaced stacking (energy, −69.5 and −77.3 kJ mol−1for the molecules A and B, respectively) and tetrel bonding interactions (energy, −43.8 kJ mol−1). In2.2H2O, the symmetrical units are stacked to show weak noncovalent interactions. The magnetic property of2.2H2Owas investigated based on the cubane [Cu4O4] core and discussed in detail, resulting in the exchange coupling parameter [(J1(short Cu⋯Cu distances) = −110.1(1) cm−1,J2(long Cu⋯Cu distances) = −27.1(2) cm−1)] that indicate a strong antiferromagnetic interaction between tetranuclear copper(ii) ions through μ-phenolate linkers, which is a result of the interaction of dx2−y2orbitals in the square plane. The EPR study is concomitant with the results of magnetism. Thus, it could be a potential material in the field of antiferromagnetic spintronics as well. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021.

Fulltext

New Journal of Chemistry

Tetranuclear copper(ii) cubane complexes derived from self-assembled 1,3-dimethyl-5-(o-phenolate-azo)-6-aminouracil: structures, non-covalent interactions and magnetic property

Direct and Telescopic Mechanochemical Synthesis of Higher-order Organic-Inorganic Hybrid Cocrystals: Tuning Order, Functionality and Size in Cocrystal Design

Inorganic macrocycles remain largely underdeveloped compared with their organic counterparts due to the challenges involved in their synthesis. Among them, cyclodiphosphazane macrocycles have shown to be promising candidates for supramolecular chemistry applications due to their ability to encapsulate small molecules or ions within their cavities. However, further developments have been handicapped by the lack of synthetic routes to high-order cyclodiphosphazane macrocycles. Moreover, current approaches allow little control over the size of the macrocycles formed. Here we report the synthesis of high-order oxygen-bridged phosphazane macrocycles via a “3 + n cyclisation” (n = 1 and 3). Using this method, an all-PIII high-order hexameric cyclodiphosphazane macrocycle was isolated, displaying a larger macrocyclic cavity than comparable organic crown-ethers. Our approach demonstrates that increasing building block complexity enables precise control over macrocycle size, which will not only generate future developments in both the phosphazane and main group chemistry but also in the fields of supramolecular chemistry. © 2021, The Author(s).

Communications Chemistry

Size-control in the synthesis of oxo-bridged phosphazane macrocycles via a modular addition approach

The ruthenacyclic carbamoyl complexes [RuBr(2-NHC(O)C5H3N-4-R)(CO)2(MeCN)] in which the 4-position of the pyridinyl ring is derivatized, have been synthesized. These are ruthenium-based structural mimics of the natural [Fe]-hydrogenase metal cofactor. The derivative with R = H reacts with phosphine to form a disubstituted product [RuBr(2-NHC(O)C5H4N)(CO)(PPh2SPh)2]. © 2020 Elsevier Ltd

Ruthenacyclic carbamoyl mimics of the [Fe]-hydrogenase active site: Derivatisation at the 4-position of the pyridinyl ring

A mononuclear tetrahedral Zn(II) complex [Zn(L)2](1)[HL = 2-(benzylimino)methyl)phenol] with phenol based bi-dentate N,O donor ligand have been prepared. The compound is characterized by various spectroscopic tools and the structure of the complex is solved by single crystal X-ray diffractometer. The tetrahedral Zn(II) complex crystallized in monoclinic space group I2/awith a = 12.2908(3) (Å), b = 9.1041(2) (Å), c = 19.9812(7) and β = 96.1466(10)°.Cyclic voltametric study of the complex 1 gives an irreversible oxidation peak due to ligand based oxidation of the phenol moiety to the phenoxyl radical. This compound also shows a strong emission band at 455 nm. The reported Zn(II) complex exhibits catecholase activity in methanol solvent under aerobic condition.The Kcatvalue for 1 in methanol is 8.411 × 103 h−1. The conversion of 3,5-di-tert-butyl catechol (3,5 DTBC) to 3,5-di-tert-butyl quinone (3,5 DTBQ) is catalysed by mono nuclear Zn(II) complex and the reaction proceeds through the generation of ligand centered phenoxyl radical. © 2020 Elsevier B.V.

Journal of Molecular Structure

Synthesis, structure, luminescent properties and catecholase activity of Zn(II) complex with N, O chelating agent

Four copper(II) carboxylate complexes, namely [Cu2(μ-3,5-dinitrobenzoate-O,O')4(4-(dimethylamino)benzaldehyde)2] (1), [Cu2(μ-benzoate-O,O')4(benzoic acid)2] (2), [Cu2(μ-benzoate-O,O')4(H2O)2] [Cu(benzoate-O,O')2(imz)2].2H2O (3) and [Cu(benzoate-O,O')2(2-Me-imz)2] (4) (imz = imidazole, 2-Me-imz = 2-methyl-imidazole), were synthesized and comprehensively characterized by elemental analysis, spectroscopic methods, single crystal X-ray diffraction, cyclic voltammetry (CV), topological analysis as well as theoretical studies. Single crystal X-ray diffraction revealed that products 1 and 2 are dinuclear paddle-wheel complexes, compound 3 is a co-crystal containing mononuclear and dinuclear blocks, while compound 4 is a mononuclear complex. Hirshfeld surface analysis of the compounds rationalized different types of hydrogen bonds, which also lead to the generation of H-bonded networks in 3 and 4. Their topological analysis disclosed a uninodal 4-connected 2D layer with sql topology in 3 and a uninodal 2-connected 1D chain with 2C1 topology in 4. The interaction of 1–4 with calf thymus DNA was investigated by UV–visible and fluorescence spectroscopy, revealing a moderately strong non-intercalative mode of interaction. In vitro cytotoxicity study of the complexes on HepG2 (human liver hepatocellular carcinoma) cell lines revealed a significant inhibition activity. Electrochemical study of the complexes in CH3CN (1–3) and DMSO (4) solution showed a one electron transfer corresponding to Cu(III)Cu(II)/Cu(II)Cu(II) and Cu(II)Cu(II)/Cu(I)Cu(II) redox couples. The ΔE and Ipa/Ipc values suggest that the redox couples are quasireversible. The DFT study was performed to further rationalize the crystal structures and nuclearity of the obtained copper(II) complexes. © 2021 Elsevier B.V.

Inorganica Chimica Acta

Synthesis, characterization, DNA binding ability, in vitro cytotoxicity, electrochemical properties and theoretical studies of copper(II) carboxylate complexes