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Four new nickel (II) complexes with bis(benzimidazole)thio- and selenoether-based ligands have been synthesized and characterized in the solid state by elemental analysis, IR, magnetic susceptibility and X-ray crystallography, and in solution by FAB + mass spectrometry, UV-vis spectroscopy and cyclic voltammetry. Single-crystal X-ray diffraction analysis of the compounds revealed octahedral geometries for all nickel centers. Three of the four complexes are dimers with chloride bridges between the two Ni(II) ions. However, in solution all complexes have a monomeric formulation, based on mass spectrometry and osmometry measurements. The complexes were also screened for their cytotoxic activity on human cell lines (HeLa, SK-LU-1 and HEK-293), and compared with a related Cu(II) complex., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Two cytotoxic copper(II) complexes with N-H and N-methylated benzimidazole-derived ligands (Cu-L 1 and Cu-L 1Me ; L 1 =bis(2-methylbenzimidazolyl)(2-methylthioethyl)amine, L 1Me =bis(1-methyl-2-methylbenzimidazolyl)(2-methylthioethyl)amine) were synthesized and exposed to human erythrocytes and molecular models of its membrane. The latter were bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), classes of lipids present in the external and internal moieties of the human red cell membrane, respectively. Scanning electron microscopy (SEM) of erythrocytes incubated with solutions of both Cu(II) complexes showed that they induced morphological changes to the normal cells to echinocytes, and hemolysis at higher concentrations. Real-time observation of the dose-dependent effects of the complexes on live erythrocytes by defocusing microscopy (DM) confirmed SEM results. The formation of echinocytes implied that complex molecules inserted into the outer moiety of the red cell membrane. X-ray diffraction studies on DMPC and DMPE showed that none of these complexes interacted with DMPE and only Cu-L 1 interacted with DMPC. This difference was explained by the fact that Cu-L 1Me complex is more voluminous than Cu-L 1 because it has two additional methyl groups; on the other hand, DMPC molecule has three methyl groups in its bulky terminal amino end. Thus, by steric hindrance Cu-L 1Me molecules cannot intercalate into DMPC bilayer, which besides is present in the gel phase. These results, together with the increased antiproliferative capacity of the N-methylated complex Cu-L 1Me over that of Cu-L 1 are rationalized mainly based on its higher lipophilicity., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Two cytotoxic copper(II) complexes with N-H and N-methylated benzimidazole-derived ligands (Cu-L(2) and Cu-L(2Me)) were synthesized and made to interact with human erythrocytes and molecular models of their plasmatic membranes. The latter consisted in lipid bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), lipids of the types present in the outer and inner monolayers of the human erythrocyte membrane, respectively. Initial assessment of the interaction of the complexes with DMPC and DMPE consisted of X-ray diffraction studies, which showed preferential interactions with the former. Scanning electron microscopy (SEM) of erythrocytes incubated with solutions of the Cu(II) complexes evidenced deformation of the cells to stomatocytes and knizocytes by Cu-L(2) and Cu-L(2Me) due to interactions with the inner and outer leaflets of the cell membranes, respectively. This was further confirmed by real-time observation of the dose-dependent effects of the complexes on live erythrocytes by defocusing microscopy (DM). The combined observations, including the increased antiproliferative activity of the N-methylated complex Cu-L(2Me) over that of Cu-L(2) is rationalized based on the higher lipophilicity of the former. This property would facilitate passive diffusion of Cu-L(2Me) through the cell membrane, particularly in the initial stages when the DMPC-rich outer leaflet is involved. In contrast, the benzimidazole N-H groups of Cu-L(2) may participate in hydrogen bonding with DMPE polar groups; this result is consistent with the formation of stomatocyte induced by the latter complex., (Copyright © 2015 Elsevier Inc. All rights reserved.)

A series of Cu(+) complexes with ligands that feature varying numbers of benzimidazole/thioether donors and methylene or ethylene linkers between the central nitrogen atom and the thioether sulfur atoms have been spectroscopically and electrochemically characterized. Cyclic voltammetry measurements indicated that the highest Cu(2+)/Cu(+) redox potentials correspond to sulfur-rich coordination environments, with values decreasing as the thioether donors are replaced by nitrogen-donating benzimidazoles. Both Cu(2+) and Cu(+) complexes were studied by DFT. Their electronic properties were determined by analyzing their frontier orbitals, relative energies, and the contributions to the orbitals involved in redox processes, which revealed that the HOMOs of the more sulfur-rich copper complexes, particularly those with methylene linkers (-N-CH2-S-), show significant aromatic thioether character. Thus, the theoretically predicted initial oxidation at the sulfur atom of the methylene-bridged ligands agrees with the experimentally determined oxidation waves in the voltammograms of the NS3- and N2S2-type ligands as being ligand-based, as opposed to the copper-based processes of the ethylene-bridged Cu(+) complexes. The electrochemical and theoretical results are consistent with our previously reported mechanistic proposal for Cu(2+)-promoted oxidative C-S bond cleavage, which in this work resulted in the isolation and complete characterization (including by X-ray crystallography) of the decomposition products of two ligands employed, further supporting the novel reactivity pathway invoked. The combined results raise the possibility that the reactions of copper-thioether complexes in chemical and biochemical systems occur with redox participation of the sulfur atom., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene)amine (L(1)), bis(2-methylbenzimidazolyl)benzylamine (L(2)), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (L(3)), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me(2)L(2)), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me(2)L(3)) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L(3) and Me(2)L(3) give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu(2+) complexes [L(1)CuCl(2)] (1), [L(2)CuCl(2)] (2) and [Me(2)L(3)CuCl]ClO(4) (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu(+) analogues [L(1)Cu]ClO(4), [L(2)Cu]ClO(4), [L(3)Cu]ClO(4) (4-6), [BOC(2)L(1)Cu(NCCH(3))]ClO(4) (4(BOC)), [Me(2)L(2)Cu(NCCH(3))(2)]PF(6) (5(Me)) and [Me(2)L(3)Cu](2)(ClO(4))(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu(+) ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl)amine-Cu(2+)/Cu(+) systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl)amine-derived ligands. Based on these observations, the N(3) or N(3)S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [Me(2)L(2)Cu(NCCH(3))(2)](+) (5(Me)) and [Me(2)L(3)Cu](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu(+) centre in 6(Me) appears to be more selective in the generation of O(2)˙(-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O(2) reactions.

Discrepancies regarding the coordination environment, donor atoms, nuclearity, and oxidation state of the active site of particulate methane monooxygenase (pMMO), a copper‐dependent enzyme capable of activating the strong C−H bond of methane, persist despite numerous structural and spectroscopic studies. To address the proposed mono‐ (CuII) or bimetallic (2CuI) nature of the so‐called CuB site, we report the bis(benzimidazole)‐based NMe−N,N'‐(1‐Me‐2‐CH2C7H4N2)2C6H4 ligand (N4) and its copper complexes. In the solid state [Cu(N4)(ClO4)]ClO4 features tetragonal geometry defined by the chelating ligand and an axial perchlorate; geometric and EPR parameters are very close to those reported for the CuB site. Attempts to obtain a dicopper(I) analog resulted in [Cu(N4)][CuCl2], based on spectroscopic, electrochemical, and ESI‐MS data. Although these results support the assignment of CuB as a monometallic site, air exposure of [Cu(N4)][CuCl2] leads to ligand oxidation in the structurally characterized [Cu(N4=O)Cl], raising the possibility of distorted tetragonal Cu(I) centers activating O2 and oxidizing substrates, in C−H activation chemistry that may take place at CuB. [ABSTRACT FROM AUTHOR]

The aim to access linked tetravanadate [V4O12]4− anion with mixed copper(II) complexes, using α-amino acids and phenanthroline-derived ligands, resulted in the formation of four copper(II) complexes [Cu(dmb)(Gly)(OH2)]2[Cu(dmb)(Gly)]2[V4O12]·9H2O (1) [Cu(dmb)(Lys)]2[V4O12]·8H2O (2), [Cu(dmp)2][V4O12]·C2H5OH·11H2O (3), and [Cu(dmp)(Gly)Cl]·2H2O (4), where dmb = 4,4′-dimethioxy-2,2′-bipyridine; Gly = glycine; Lys = lysine; and dmp = 2,9-dimethyl-1,10-phenanthroline. The [V4O12]4− anion is functionalized with mixed copper(II) units in 1 and 2; while in 3, it acts as a counterion of two [Cu(dmp)]2+ units. Compound 4 crystallized as a unit that did not incorporate the vanadium cluster. All compounds present magnetic couplings arising from Cu⋯O/Cu⋯Cu bridges. Stability studies of water-soluble 3 and 4 by UV–Vis spectroscopy in cell culture medium confirmed the robustness of 3, while 4 appears to undergo ligand scrambling over time, resulting partially in the stable species [Cu(dmp)2]+ that was also identified by electrospray ionization mass spectrometry at m/z = 479. The in vitro cytotoxicity activity of 3 and 4 was determined in six cancer cell lines; the healthy cell line COS-7 was also included for comparative purposes. MCF-7 cells were more sensitive to compound 3 with an IC50 value of 12 ± 1.2 nmol. The tested compounds did not show lipid peroxidation in the TBARS assay, ruling out a mechanism of action via reactive oxygen species formation. Both compounds inhibited cell migration at 5 µM in wound-healing assays using MCF-7, PC-3, and SKLU-1 cell lines, opening a new window to study the anti-metastatic effect of mixed vanadium–copper(II) systems. [ABSTRACT FROM AUTHOR]

Polysaccharide oxidative depolymerization is highly desirable to achieve recalcitrant biomass valorization. Inspired by recently discovered Lytic Polysaccharide Monooxygenases, mononuclear copper complexes have been prepared and studied in the literature. However, the activities were evaluated on different substrates and under various conditions. In this work we intended to establish a robust and reproducible activity assay, in aqueous solution at a pH close from neutrality and under mild conditions. We have evaluated several complexes on substrates of increasing complexity: the model substrate para‐nitrophenyl‐β‐D‐glucopyranoside (p‐NPG), cellobiose (glucose dimer), as well as on extended substrates (chitin, cellulose and bagasse from agave). The different assays were compared and proof‐of‐concept that bioinspired complexes can oxidatively promote polysaccharide depolymerization was obtained. Finally, we measured level of hydroxyl radicals released by the complexes under comparable experimental conditions and mechanistic pathways are discussed. [ABSTRACT FROM AUTHOR]

Functionalization of the phenolic rim of p‐tert‐butylcalix[8]arene with phenanthroline to create a cavity leads to formation of two regioisomers. Substitution of positions 1 and 5 produces the known C2v‐symmetric regioisomer 1,5‐(2,9‐dimethyl‐1,10‐phenanthroyl)‐p‐tert‐butylcalix[8]arene (L1,5), while substitution of positions 1 and 4 produces the Cs‐symmetric regioisomer 1,4‐(2,9‐dimethyl‐1,10‐phenanthroyl)‐p‐tert‐butylcalix[8]arene (L1,4) described herein. [Cu(L1,4)I] was synthesized from L1,4 and CuI in good yield and characterized spectroscopically. To evaluate the effect of its cavity on catalysis, Ullmann‐type C−S coupling was chosen as proof‐of‐concept. Selected aryl halides were used, and the results compared with the previously reported Cu(I)/L1,5 system. Only highly activated aryl halides generate the C−S coupling product in moderate yields with the Cu(I)/L1,4 system. To shed light on these observations, detailed computational investigations were carried out, revealing the influence of the calix[8]arene macrocyclic morphology on the accessible conformations. The L1,4 regioisomer undergoes a deformation that does not occur with L1,5, resulting in an exposed catalytic center, presumably the cause of the low activity of the former system. The 1,4‐connectivity was confirmed in the solid‐state structure of the byproduct [Cu(L1,4−H)(CH3CN)2] that features Cu(I) coordinated inside a cleft defined by the macrocyclic framework. [ABSTRACT FROM AUTHOR]

Development of C−N coupling methodologies based on Earth‐abundant metals is a promising strategy in homogeneous catalysis for sustainable processes. However, such systems suffer from deactivation and low catalytic activity. We here report that encapsulation of Cu(I) within the phenanthroyl‐containing calix[8]arene derivative 1,5‐(2,9‐dimethyl‐1,10‐phenanthroyl)‐2,3,4,6,7,8‐hexamethyl‐p‐tert‐butylcalix[8]arene (C8PhenMe6) significantly enhances C−N coupling activity up to 92 % yield in the reaction of aryl halides and aryl amines, with low catalyst loadings (2.5 % mol). A tailored multiscale computational protocol based on Molecular Dynamics simulations and DFT investigations revealed an oxidative addition/reductive elimination process of the supramolecular catalyst [Cu(C8PhenMe6)I]. The computational investigations uncovered the origins of the enhanced catalytic activity over its molecular analogues: Catalyst deactivation through dimerization is prevented, and product release facilitated. Capturing the dynamic profile of the macrocycle and the impact of non‐covalent interactions on reactivity allows for the rationalization of the behavior of the flexible supramolecular catalysts employed. [ABSTRACT FROM AUTHOR]

This minireview presents efforts of synthetic chemists to mimic the active site of the copper monooxygenase enzymes peptidylglycine α‐hydroxylating monooxygenase (PHM), dopamine β‐monooxygenase (DβM), and tyramine β‐monooxygenase (TβM), all of which feature copper‐thioether ligation in their resting states. These monooxygenases are involved in the initial activation of O2 to generate neurotransmitters by the selective activation of C−H bonds of their corresponding substrates, resulting in subsequent hydroxylation. Attempts to emulate the N2S donor set provided by the two histidines and the methionine residues that coordinate to copper in the active site employ N2S and N3S‐type ligands, with the latter ones providing the best conditions for testing the reactivity of their CuI complexes with dioxygen. Identification of CuII‐superoxos as capable agents for C−H activation has provided support for these species as the key reactive intermediates in the enzymatic systems. Synthetic end‐on [CuII‐η1‐O2.−] and side‐on [CuII‐η2‐O2.−] cupric superoxos are capable of such transformations, which is related to the open question of whether the methionine S‐donor may act as a hemilabile ligand in biological systems. [ABSTRACT FROM AUTHOR]

Bis(benzimidazole)amine‐based copper complexes, with structural similarities to the active sites of Lytic Polysaccharide Monooxygenase enzymes (LPMOs), were tested for the oxidative degradation of cellulose. Spectroscopic characterization of the complexes, as well as structural authentication of one of them, confirm a tetragonal coordination environment with 3 nitrogen donors, as well as a thioether in axial positions. Aqueous oxidative degradation of cellulose was achieved with the CuII complexes and H2O2 as oxidant through putative cupric‐hydroperoxo intermediates. Conversion of cellulose was achieved in up to 67 % yield of soluble oligosaccharide derivatives at ambient temperature and pressure. The products were analyzed in aqueous solution by HPLC‐MS, confirming oxidative depolymerization of cellulose under ambient conditions, in an analogous fashion to LPMOs. [ABSTRACT FROM AUTHOR]

[N,N‐bis(1‐methyl‐2‐benzimidazolyl)methyl‐N‐(bis‐2‐pyridylmethyl)amine] (L1) and [N,N‐bis(2‐quinolylmethyl)‐N‐bis(2‐pyridyl)methylamine] (L2) were employed to prepare CuII and CuI complexes for spectroscopic and structural characterization. [L1CuII(H2O)](NO3)2 and [L2CuII(NO3)]NO3 have Jahn–Teller distorted octahedral geometries and give rise to isotropic EPR spectra in frozen solution. [L1CuI(CH3CN)]OTf and [L2CuI(CH3CN)]OTf have distorted trigonal bipyramidal and tetrahedral solid‐state structures, respectively. The N‐donors display labile behavior in solution, based on variable‐temperature 1H NMR studies. Addition of trimethylamine N‐oxide (Me3NO) to solutions of [L1CuI(CH3CN)]OTf and [L2CuI(CH3CN)]OTf resulted in diamagnetic species tentatively assigned as the corresponding adducts upon replacement of coordinated acetonitrile, based on 1H NMR spectroscopy. Heating [L1CuI(CH3CN)]OTf to 50–60 °C in the presence of Me3NO resulted in its cupric analogue [L1CuII(CH3CN)]2+, as well as a small amount of 2‐dipyridylketone, along with other oxidation by‐products. In the case of [L2CuI(CH3CN)]OTf, the reaction with Me3NO resulted in the cupric complex bis(2‐quinolinecarboxamidato)copper(II), along with 2‐dipyridylketone as oxidation products. [ABSTRACT FROM AUTHOR]

Front Cover: Conformational Effects of Regioisomeric Substitution on the Catalytic Activity of Copper/Calix[8]arene C-S Coupling (Eur. J. Inorg. Calixarenes, Conformational sampling, Copper, DFT calculations, Macrocycles Keywords: Calixarenes; Conformational sampling; Copper; DFT calculations; Macrocycles EN Calixarenes Conformational sampling Copper DFT calculations Macrocycles 1 1 1 02/23/23 20230217 NES 230217 B The Front Cover b shows the open conformer of the 1,4-phenanthroyl derivatized calix[8]arene/Cu(I) system that allows for C-S coupling to occur on the right hand side. [Extracted from the article]

Mixed N,S tripodal ligands bis(2,4-dimethylphenylthioethyl)(2-methylbenzimidazolyl)amine L 1 , bis(2,4-dimethylphenylthioethyl)(1-methyl-2-methylbenzimidazolyl)amine L 2 , and bis(1-methyl-2-methylbenzimidazolyl)(2-methylthioethyl)amine L 3 were employed to prepare the corresponding copper complexes. L 1 and L 2 associate weakly with Cu 2+ , while the reaction of CuI with L 1 affords [ L 1 CuI]. This was characterized in the solid state by the chelating tridentate coordination mode of L 1 , with a free thioether, and a terminal iodide, in contrast with the commonly observed Cu–I–Cu bridges. For L 3 , Cu + and Cu 2+ complexes are accessible as [ L 3 Cu]PF 6 , and the crystallographically characterized [ L 3 CuCl]Cl. The latter has a square pyramidal coordination around the Cu 2+ ion, with the thioether as an axial ligand that remains coordinated in solution, as evidenced by UV–Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of the chiral ligands (1S,4S)-2,5-bis(6-methylpyridyl)-diazabicyclo[2.2.1]heptane (L1 ) and (1S,4S)-2,5-bis(1-methyl-2-methylbenzimidazolyl)-diazabicyclo[2.2.1]heptane (L2 ) with CuCl2 results in the hydroxo-bridged dicopper complexes [(L1 )Cu2(μ-OH)(H2O)Cl3] (3), and [(L2 )Cu2(μ-OH)(H2O)Cl3] (4). Both chiral complexes were characterized spectroscopically, and 3 in the solid state by X-ray crystallography, confirming they are structurally related to their previously reported copper acetate analogues (1 and 2) due to their hydroxo-bridged bimetallic core. The achiral ligand analogues N,N′-bis(2-picolyl)piperazine (L3 ) and N,N′-bis(1-methyl-2-methylbenzimidazolyl)piperazine (L4 ) were employed to obtain the corresponding complexes with CuCl2, affording the chloro-bridged [(L3 )(CuCl)2(μ-Cl)2]n (5) and [(L4 )(CuCl)2(μ-Cl)2] (6), neither of which features a bridging hydroxo ligand; instead, complex 5 was structurally characterized as a coordination polymer. The acetate-derived complexes 1 and 2 are active in oxidative C–C coupling of 2,4-di-tert-butylphenol, while 3 and 4 have low activity; the achiral complexes 5 and 6, lacking a bridging hydroxo ligand, are inactive in this reaction. [Copyright &y& Elsevier]

Keywords: C-H activation; Copper; Monooxygenases; Oxidation; Thioethers EN C-H activation Copper Monooxygenases Oxidation Thioethers 1 1 1 02/01/22 20220111 NES 220111 B The Front Cover b shows the synergic action of copper and sulfur in thioether-containing copper monooxygenases that generate mammalian and invertebrate neurotransmitters. The review reports efforts of synthetic chemists to mimic the active sites of peptidylglycine -hydroxylating monooxygenase, dopamine -monooxygenase, and tyramine -monooxygenase. Front Cover: Thioether-Containing Copper Complexes as PHM, D M, and T M Model Systems (Eur. J. Inorg. [Extracted from the article]

A series of Cu+ complexes with ligands that feature varying numbers of benzimidazole/thioether donors and methylene or ethylene linkers between the central nitrogen atom and the thioether sulfur atoms have been spectroscopically and electrochemically characterized. Cyclic voltammetry measurements indicated that the highest Cu2+/Cu+ redox potentials correspond to sulfur-rich coordination environments, with values decreasing as the thioether donors are replaced by nitrogen-donating benzimidazoles. Both Cu2+ and Cu+ complexes were studied by DFT. Their electronic properties were determined by analyzing their frontier orbitals, relative energies, and the contributions to the orbitals involved in redox processes, which revealed that the HOMOs of the more sulfur-rich copper complexes, particularly those with methylene linkers (NCH2S), show significant aromatic thioether character. Thus, the theoretically predicted initial oxidation at the sulfur atom of the methylene-bridged ligands agrees with the experimentally determined oxidation waves in the voltammograms of the NS3- and N2S2-type ligands as being ligand-based, as opposed to the copper-based processes of the ethylene-bridged Cu+ complexes. The electrochemical and theoretical results are consistent with our previously reported mechanistic proposal for Cu2+-promoted oxidative CS bond cleavage, which in this work resulted in the isolation and complete characterization (including by X-ray crystallography) of the decomposition products of two ligands employed, further supporting the novel reactivity pathway invoked. The combined results raise the possibility that the reactions of copper-thioether complexes in chemical and biochemical systems occur with redox participation of the sulfur atom. [ABSTRACT FROM AUTHOR]

The reactions of mono-, bis- and tetrapicolyl-p-tert-butylcalix[4]arene derivatives functionalised in the phenolic positions (L1-L4) with copper(II) acetate resulted in the formation of discrete complexes or extended coordination polymers. The centrosymmetric dimer [Cu2(μ-O2CCH3)4(L1)2] 1, obtained with monodentate L1, has square pyramidal coordination around the copper centres and a cone conformer of monopicolyl-calix[4]arene acting as an axial ligand, with a molecule of acetonitrile hosted within its cavity. The potentially bidentate L2 acts as a monodentate ligand, affording the complex [Cu2(μ-O2CCH3)4(L2)2] 2, which based on spectroscopic and combustion analysis data has a similar coordination sphere around Cu(II). Compound L3 bridges two dicopper units in the coordination polymer [Cu2(μ-O2CCH3)4(μ-L3)]n 3, with the calixarene hosting a molecule of tetrahydrofuran. Finally, compound L4 reacts with 4 equivalents of copper(II) acetate, presumably generating a two-dimensional coordination polymer formulated as [{Cu2(μ-O2CCH3)4}2(L4)] 4. [ABSTRACT FROM AUTHOR]

Cover Feature: Cellulose Depolymerization with LPMO-inspired Cu Complexes (ChemCatChem 22/2021) Biomass, catalysis, LPMO, biomimetic, copper Keywords: biomass; catalysis; LPMO; biomimetic; copper EN biomass catalysis LPMO biomimetic copper 4654 4654 1 11/24/21 20211122 NES 211122 B The Cover Feature b represents the oxidative depolymerization of cellulose, affording cellobiose, levoglucosan, and gluconic acid as water-soluble products. [Extracted from the article]

A new macrocycle bearing tyramine arms through amide linkages, 2,2′-(2,9-dioxo-1,4,7,10-tetraazacyclotridecane-4,7-diyl)bis( N -(4-hydroxyphenethyl)acetamide) abbreviated as L13Tyra, has been synthesized with amide-coupling agents in a microwave reactor. This macrocycle involves two potential metal-coordinating and bioactive sites, i.e ., the tetraaza-macrocyclic ring (with a low basicity of the amino nitrogen) and the pendant phenol arms (with a small p K a 8.6). The Cu 2+ complex has different compositions in solid and in solution. An X-ray crystal study shows that a mononuclear complex [Cu(L13Tyra – 2H)] 0 is formed with a square coordination of two deprotonated amide nitrogen and two amino nitrogen atoms of the macrocyclic ring; a carbonyl oxygen atom from a pendant arm occupies an axial site to construct a square pyramid. UV–Vis spectrometric titrations in aqueous solutions indicate the formation of a binuclear complex [Cu 2 (L13Tyra – 4H)(H 2 O) x ] 0 in which phenolate oxygen atoms of the tyramine arms coordinate a Cu 2+ ion in addition to the coordination of the macrocyclic chelate; such a binuclear structure is maintained only in solution. The uncoordinated ligand has a high antioxidant capacity with a TEAC (Trolox equivalent antioxidant capacity) assay comparable to that of ascorbic acid, thanks to the phenolic OH of the tyramine arms. Copper(II) ion works as an inhibitor against the activity; the TEAC assay of the binuclear complex is as small as one-twentieth that of the uncoordinated ligand. Antiproliferative and cytotoxic assays with normal and cancer cell lines show no toxicity for both the ligand and its Cu 2+ complex. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of the chiral ligands (1S,4S)-2,5-bis(6-methylpyridyl)-diazabicyclo[2.2.1]heptane (L 1 ), and (1S,4S)-2,5-bis(2-methylbenzimidazolyl)-diazabicyclo[2.2.1]heptane (L 2 ) with copper(II) acetate results in the hydroxo-bridged dicopper complexes [(L 1 )Cu2(μ-OH)(H2O)(OAc)2Cl] (1-Cl·H2O), and [(L 2 )Cu(μ-OH)(H2O)(MeOH)(OAc)2]OAc (2 .H2O,MeOH). Both chiral complexes were characterized spectroscopically, as well as in the solid state by X-ray crystallography. [Copyright &y& Elsevier]

A neutral aminotrithioether interacts with CuI, generating a coordination polymer in the solid state. Electrochemical studies indicate that the ligand is prone to oxidation by CuII, which results in a novel C—C bond formation reaction. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of bispicolyl-p-tert-butylcalix[4]arene (L 1 ) functionalized in alternate phenolic positions with dimeric copper(II) acetate resulted in the formation of a hybrid organic–inorganic polymer. In the solid state, dicopper fragments are bridged by the bidentante ligand [Cu2(μ-O2CCH3)4(μ-L 1 )·C4H8O] n , with one molecule of tetrahydrofuran in the asymmetric unit. The two independent Cu(II) ions possess square pyramidal coordination geometries defined by the four acetate ligands, and a picolyl group in the axial position. [Copyright &y& Elsevier]