(Bis(terpyridine))copper(II) Tetraphenylborate: A Complex Example for the Jahn–Teller Effect

Persistent production of multiple active species with copper doped zinc gallate nanoparticles for light-independent photocatalytic degradation of organic pollutants

Photocatalysis is considered as an environmentally friendly and sustainable method as it can produce active species to degrade pollutants. However, its applications are hindered by the turbidity of pollutants and the requirements for continuous or repeated in situ irradiation. To avoid the need for continuous in situ irradiation in the photocatalytic process, herein we report the doping of Cu(II) ions into zinc gallate (ZnGa2O4) as traps to capture photo-generated electrons. In this way, long lifetime charge release and separation were effectively achieved for the persistent degradation of organic dyes in wastewater. The Cu(II) doped ZnGa2O4 (ZGC) nanoparticles with a small size about 7.7 nm synthesized via a hydrothermal method exhibited a persistent photocatalytic activity with continuous production of reactive oxygen species for at least 96 h without in situ irradiation due to its unique electronic structure and carrier transport path, and enabled to degrade 82.2 % of rhodamine B in 1 h. Further investigation revealed that the doped Cu(II) ions occupied the octahedral sites of ZGC and highly increased the persistent production and availability of active species for the persistent degradation of organic dyes under pre-illuminated conditions.

Exploring the BSA- and DNA-binding, cytotoxicity, and cell cycle evaluation of ternary copper(II)/diimine complexes with N,N-dibenzyl-N'-benzoylthiourea as promising metallodrug candidates

Four new copper(II) complexes were synthesized and characterized with the general formula [Cu(N-N)(Th)(NO3)], where N-N corresponds to the N-heterocyclic ligands 1,10-phenanthroline (phen), 2,2'-bipyridine (bipy), 4,7-diphenyl-1,10-phenanthroline (dpp), and 4,4-dimethyl-2,2'-bipyridine (dmbp) and Th represents the N,N-dibenzyl-N'-benzoylthiourea. Cytotoxic activities of the complexes against HCT116 (human colon carcinoma), HepG2 (human hepatocellular carcinoma), and non-tumor MRC-5 (human lung fibroblast) cells were investigated. The copper(II) complexes 1-4 were characterized by spectroscopic techniques while complexes 1 and 2 were studied using single-crystal X-ray diffraction as well. The complexes possessed a five-coordinated structure with one nitrate ligand as a monodentate at the axial position and two bidentate ligands N-heterocyclic and N,N-dibenzyl-N'-benzoylthiourea. The complexes showed promising IC50 values, ranging from 0.3 to 9.0 μM. Furthermore, interaction studies with biomolecules such as calf thymus DNA (ct-DNA) and Bovine Serum Albumin (BSA), which can act as possible biological targets of the complexes, were carried out. The studies suggested that the compounds interact moderately with ct-DNA and BSA. Complexes 1, 2, and 4 did not lead to cell accumulation at any stage of the cell cycle but caused a significant increase in internucleosomal DNA fragmentation. Whereas, compound 3 caused cell cycle arrest in the S phase while doxorubicin caused cell cycle arrest in the G2/M phase. The effect of structural modifications on the metal compounds was correlated with their biological properties and it was concluded that an increase in biological activity occurred with increasing the extension of the diimine ligands. Thus, complex 3 was the most promising one.

A series of entangled MOFs constructed from flexible dipyridyl piperazine and rigid dicarboxylate: interpenetration, self-penetration, and polycatenation

By employing a flexible dipyridyl piperazine and a rigid linear dicarboxylate, four MOFs with different entangled structures involving a 3D inclined polycatenane and a 3D self-penetrated framework incorporating cyclic [3]catenane were isolated.

Exotic nuclear spin behavior in dendritic macromolecules

Dendrimers are a class of branched, highly symmetric macromolecules that have been shown to be useful for a vast number of different applications. Potential uses as fluorescence sensors, in catalysis and perhaps most importantly in medical applications as drug delivery systems or cytotoxica have been proposed. Herein we report on an exotic behaviour of the nuclear spins in a dendritic macromolecule in the presence of different paramagnetic ions. We show that the stability of the long lived nuclear singlet state, is affected by the presence of Cu(II), whereas other ions did not have any influence at all. This effect could not be observed in the case of a simple tripeptide, in which the nuclear singlet stability was influenced by all investigated paramagnetic ions, a potentially useful effect in the development of Cu(II) selective probes. By adding a fluorescent marker to our molecule we could show that the nuclear singlet multimer (NUSIMER) is taken up by living cells. Furthermore we were able to show that nuclear singlet state NMR can be used to investigate the NUSIMER in the presence of living cells, showing that an application in in vivo NMR can be feasible.

Two Faces of the Same Coin: Coupling X-Ray Absorption and NMR Spectroscopies to Investigate the Exchange Reaction Between Prototypical Cu Coordination Complexes

The satisfactory rationalization of complex reactive pathways in solution chemistry may greatly benefit from the combined use of advanced experimental and theoretical complementary methods of analysis. In this work, we combine X-Ray Absorption and ¹ H NMR spectroscopies with state-of-the-art Multivariate Curve Resolution and theoretical analyses to gain a comprehensive view on a prototypical reaction involving the variation of the oxidation state and local structure environment of a selected metal ion coordinated by organic ligands. Specifically, we investigate the 2-cyano-2-phenylpropanoic acid reduction of the octahedral complex established by the Cu²⁺ ion with terpyridine to the tetrahedral complex formed by Cu⁺ and neocuproine. Through our interdisciplinary approach we gain insights into the nature, concentration time evolution and structures of the key metal (XAS measurements) and organic (¹ H NMR measurements) species under reaction. We believe our method may prove to be useful in the toolbox necessary to understand the mechanisms of reactive processes of interest in solution.

Homo- and heteroleptic trimethoxy terpyridine–Cu(ii) complexes: synthesis, characterization, DNA/BSA binding, DNA cleavage and cytotoxicity studies

In the current study, four novel mononuclear Cu(ii) complexes with terpyridine (L) and different co-ligands (phen, bipy, and imd) were synthesized and characterized in detail, whereLis 4′-(3,4,5-trimethoxyphenyl)-2,2′:6′,2′′-terpyridine.

Tremblay A, Maris T, Leal do Santos S, Venancio EC, Ferreira Santos S, Duong A. Programmed Molecular Construction: Driving the Self-Assembly by Coordination and Hydrogen Bonds Using 6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine with M(NO3)2 Salts

A new series of hydrogen-bonded metallotecton networks 6-9 of the general formula [M(2)₂(NO₃)₂] were obtained from the reaction of 6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine 2 with transition-metal ions [M: Co(II), Ni(II), Cu(II), and Zn(II)]. Their supramolecular networks and associated properties were characterized by single-crystal and powder X-ray diffraction, IR, solid-state UV-vis spectroscopy, and thermogravimetric analysis associated with differential scanning calorimetry. On the basis of standard patterns of coordination involving 2,2'-bipyridine and simple derivatives, compound 2 binds transition-metal ions with predictable constitution and the diaminotriazinyl (DAT) groups serve orthogonally to ensure the intermetallotecton interactions by hydrogen bonding according to well-established motifs I-III. As expected, compound 2 formed octahedral 2:1 metallotectons with M(NO₃)₂, and further self-assembled by hydrogen bonding of the DAT groups to produce pure, crystalline, homogeneous, and thermally stable materials. In these structures, nitrate counterions also play an important role in the cohesion of intermetallotectons to form two-dimensional and three-dimensional networks. These results illustrated the effectiveness of the synthetic approach to create a wide range of novel ordered materials with controllable architectures and tunable properties achieved by varying the central metal ion. Crystal morphologies of 6-9 were also investigated by scanning electron microscopy and calculation using Bravais-Friedel-Donnay-Harker method from their single-crystal structure.

Mimicking 2,2′:6′,2′′:6′′,2′′′-quaterpyridine complexes for the light-driven hydrogen evolution reaction: synthesis, structural, thermal and physicochemical characterizations

The synthetic difficulties associated with quaterpyridine (qtpy) complexes have limited their use in the formation of various metallosupramolecular architectures in spite of their diverse structural and physicochemical properties. Providing a new facile synthetic route to the synthesis of functionalised qtpy mimics, we herein report the synthesis of three novel –NH₂ functionalized qtpy-like complexes 12–14 with the general formula M(C₁₆H₁₄N₁₂)(NO₃)₂ (M = Co(ii), Ni(ii) and Cu(ii)) in high yield and purity. Characterization of these complexes has been done by single crystal X-ray diffraction (SCXRD), thermogravimetric analysis, UV-Vis, infrared, mass spectrometry and cyclic voltammetry. As indicated by SCXRD, in all the synthesized complexes, the metal ions show a strongly distorted octahedral coordination geometry and typical hydrogen bonding networks involving DAT groups. In addition, complexes 12–14 have been analyzed as potential photocatalysts for hydrogen evolution reaction (HER) displaying good turnover numbers (TONs). Hydrogen produced from these photocatalysts can serve as the possible alternative for fossil fuels. To the best of our knowledge, this is the only study showcasing –NH₂ functionalized qtpy-like complexes of Co(ii), Ni(ii) and Cu(ii) and employing them as photocatalysts for HER. Thus, a single proposed strategy solves two purposes-one related to synthesis while second is related to our environment.

Facile synthesis of three novel –NH₂ functionalized qtpy-like complexes, their characterizations and study of their photocatalytic properties for hydrogen evolution reaction.

Isolation of EPR spectra and estimation of spin-states in two-component mixtures of paramagnets

The presence of multiple paramagnetic species can lead to overlapping electron paramagnetic resonance (EPR) signals. This complication can be a critical obstacle for the use of EPR to unravel mechanisms and aid the understanding of earth abundant metal catalysis. Furthermore, redox or spin-crossover processes can result in the simultaneous presence of metal centres in different oxidation or spin states. In this contribution, pulse EPR experiments on model systems containing discrete mixtures of Cr(i) and Cr(iii) or Cu(ii) and Mn(ii) complexes demonstrate the feasibility of the separation of the EPR spectra of these species by inversion recovery filters and the identification of the relevant spin states by transient nutation experiments. We demonstrate the isolation of component spectra and identification of spin states in a mixture of catalyst precursors. The usefulness of the approach is emphasised by monitoring the fate of the chromium species upon activation of an industrially used precatalyst system.

Crystal structure of [Cu(tmpen)](BF4)2 {tmpen is N,N,N',N'-tetra-kis-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine}

The mononuclear copper title complex {N,N,N',N'-tetra-kis-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine-κ6N}copper(II) bis-(tetra-fluorido-borate), [Cu(C30H36N6)](BF4)2, is conveniently prepared from the reaction of Cu(BF4)2·6H2O with N,N,N',N'-tetra-kis-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine (tmpen) in aceto-nitrile at room temperature in air. The complex shows a distorted octa-hedral environment around the CuII cation (site symmetry 2) and adopts the centrosymmetric space group C2/c. The presence of the 6-methyl substituent hinders the approach of the pyridine group to the CuII core. The bond lengths about the CuII atom are significantly longer than those of analogues without the 6-methyl substituents.

Unusual crystal structure and chirality of uridine 5′-monophosphate coordination polymer

The auxiliary ligand effect in the structure and charility of uridine 5′-monophosphate coordination polymer was investigated.

Single and double nitroxide labeled bis(terpyridine)-copper(ii): influence of orientation selectivity and multispin effects on PELDOR and RIDME

The structure of Jahn–Teller distorted copper–nitroxide complexes in neutral and acidic solutions is investigated using EPR distance measurements taking into account the influence of orientation selectivity and multispin effects.

Crystal structure of 4'-{[4-(2,2':6',2''-terpyrid-yl-4'-yl)phen-yl]ethyn-yl}biphenyl-4-yl (2,2,5,5-tetra-methyl-1-oxyl-3-pyrrolin-3-yl)formate benzene 2.5-solvate

The title compound, C44H35N4O3·2.5C6H6 (1), consists of a terpyridine and a N-oxylpyrroline-3-formate group separated by an aromatic spacer, viz. 4-(phenyl-ethyn-yl)-1,1'-biphenyl. It crystallized in the triclinic space group P-1 with two and a half benzene solvate mol-ecules (one benzene mol-ecule is located about an inversion center), while the di-chloro-methane solvate (2) of the same mol-ecule [Ackermann et al. (2015 ▸). Chem. Commun. 51, 5257-5260] crystallized in the tetra-gonal space group P42/n, with considerable disorder in the mol-ecule. In (1), the terpyridine (terpy) group assumes an all-trans conformation typical for terpyridines. It is essentially planar with the two outer pyridine rings (B and C) inclined to the central pyridine ring (A) by 8.70 (15) and 14.55 (14)°, respectively. The planes of the aromatic spacer (D, E and F) are nearly coplanar with dihedral angles D/E, D/F and E/F being 3.42 (15), 5.80 (15) and 4.00 (16)°, respectively. It is twisted with respect to the terpy group with, for example, dihedral angle A/D being 24.48 (14)°. The mean plane of the N-oxylpyrroline is almost normal to the biphenyl ring F, making a dihedral angle of 86.57 (16)°, and it is inclined to pyridine ring A by 72.61 (15)°. The intra-molecular separation between the O atom of the nitroxyl group and the N atom of the central pyridine ring of the terpyridine group is 25.044 (3) Å. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, forming inversion dimers. The dimers stack along the c axis forming columns. Within and between the columns, the spaces are occupied by benzene mol-ecules. The shortest oxygen-oxygen separation between nitroxyl groups is 4.004 (4) Å. The details of the title compound are compared with those of the di-chloro-methane solvate (2) and with the structure of a related mol-ecule, 4'-{4-[(2,2,5,5-tetra-methyl-N-oxyl-3-pyrrolin-3-yl)ethyn-yl]phen-yl}-2,2':6',2''-terpyridine (3), which has an ethynylphenyl spacer [Meyer et al. (2015). Acta Cryst. E71, 870-874].