Topological insights in polynuclear Ni/Na coordination clusters derived from a schiff base ligand

This article presents the syntheses, crystal structures, topological features and magnetic properties of two NiII/NaI coordination clusters (CCs) formulated [NiII3Na(L1)3(HL1 (MeOH)2] (1) and [NiII6Na(L1)5(CO3)(MeO (MeOH)3(H2O)3]·4(MeOH) 2(H2O) [2 4(MeOH) 2(H2O)] where H2L1 is the semi rigid Schiff base ligand (E)-2-(2-hydroxy-3 methoxybenzylideneamino)-phenol). Compound 1 possesses a rare NiII3NaI cubane (3M4-1) topology and compound 2 is the first example in polynuclear Ni/Na chemistry that exhibits a 2,3,4M7-1 topology

Establishing Structure–Activity Relationships in Photocatalytic Systems by Using Nickel Bis(dithiolene) Complexes as Proton Reduction Catalysts

Herein, we present an artificial photocatalytic system for H2 evolution based on a series of proton reduction catalysts, namely [Ni{S2C2(Ph)2}2] (1), [Ni{S2C2(Ph)2}2](NEt4) (1–), [Ni{S2C2(Ph)(Ph–OCH3-4)}2] (2), [Ni{S2C2(Ph)(Ph–OCH3-4)}2](NEt4) (2–), [Ni{S2C2(Ph–OCH3-4)2}2] (3) and [Ni{S2C2(Ph–OCH3-4)2}2](NEt4) (3–), [Ni(mnt)2] (NBu4) (4–), [Ni(mnt)(S2C2(Ph)2)](NBu4) (5–). These complexes are different of both in charge and the substituents on dithiolene ligand and represent a group of active catalysts for the reduction of protons with high TONs. A series of ReI complexes, [ReBr(CO)3 (bpy)], [ReCl(CO)3(bpy)], [Re(NCS)(CO3)(bpy)], [ReBr(CO)3(amphen)] and [ReBr(CO)3 (pq)] were used as photosensitizers, in combination with triethanolamine as a sacrificial electron donor and acetic acid as a proton source. The differences of the ligands in the electron donating properties and reactivity are discussed in the light of the experimental data. We also present the physicochemical characterization of a previously reported heteroleptic monoanionic complex (5–), by UV/Vis spectroscopy, FTIR spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Experimental and Theoretical Insight into Electrocatalytic Hydrogen Evolution with Nickel Bis(aryldithiolene) Complexes as Catalysts

A series of neutral and monoanionic nickel dithiolene complexes with p-methoxyphenyl-substituted 1,2-dithiolene ligands have been prepared and characterized with physicochemical methods. Two of the complexes, the monoanion of the symmetric [Ni{S2C2(Ph-p-OCH3)2}2] (3-) with NBu4+ as a counterion and the neutral asymmetric [Ni{S2C2(Ph)(Ph-p-OCH3)}2] (2), have been structurally characterized by single-crystal X-ray crystallography. All complexes have been employed as proton-reducing catalysts in N,N-dimethylformamide with trifluoroacetic acid as the proton source. The complexes are active catalysts with good faradaic yields, reaching 83% for 2 but relatively high overpotential requirements (0.91 and 1.55 V measured at the middle of the catalytic wave for two processes observed depending on the different routes of the mechanism). The similarity of the experimental data regardless of whether the neutral or anionic form of the complexes is used indicates that the neutral form acts as a precatalyst. On the basis of detailed density functional theory calculations, the proposed mechanism reveals two different main routes after protonation of the dianion of the catalyst in accordance with the experimental data, indicating the role of the concentration of the acid and the influence of the methoxy groups. Protonation at sulfur seems be more favorable than that at the metal, which is in marked contrast with the catalytic mechanism proposed for analogous cobalt dithiolene complexes. © 2015 American Chemical Society

Reactivity and mechanism of photo-and electrocatalytic hydrogen evolution by a diimine copper(I) complex

The tetrahedral copper(I) diimine complex [Cu(pq)2]BF4 displays high photocatalytic activity for the H2 evolution reaction with a turnover number of 3564, thus representing the first type of a Cu(I) quinoxaline complex capable of catalyzing proton reduction. Electrochemical experiments indicate that molecular mechanisms prevail and DFT calculations provide in-depth insight into the catalytic pathway, suggesting that the coordinating nitrogens play crucial roles in proton exchange and hydrogen formation. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Cyanate groups in higher oxidation state metal cluster chemistry: Mixed-valence (II/III) Mn16 and Mn18 clusters

The employment of cyanato (OCN-) group in high oxidation state manganese cluster chemistry, in conjunction with carboxylate ions and the organic chelating/bridging ligand 2-(hydroxymethyl)pyridine (hmpH), is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)) and [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). The 2:1:1:1 reactions of Mn(O2CMe)2·4H2O, hmpH, NaOCN and NEt3 in solvent MeOH or EtOH afford the isostructural complexes [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)). The [Mn16(μ4-O)4(μ3-O)4(μ-OMe)4(μ3-OR)6(μ-OR)6]10+ core of representative complex 1 comprises a MnII4MnIII4 double-cubane subunit attached on either side to two symmetry-related MnIIMnIII3 defective dicubanes. A similar reaction of Mn(O2CR)2·4H2O, hmpH, NaOCN and NEt3, but in solvent MeCN, led instead to the formation of [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). Compounds 3 and 4 are very similar to each other and can be described as a central [MnIII4(μ-O)6] rodlike subunit attached on either side to two symmetry-related [Mn7O9] subunits. Variable-temperature, solid-state dc and ac magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions in all compounds, and possible S = 2 or 1 (for 1 and 2) and S = 0 (for 3 and 4) ground state spin values. The combined results demonstrate the ability of cyanato groups to facilitate the formation of new polynuclear MnII/III complexes with structures different than these obtained from the use of the related azides

Synthesis, characterization and cytotoxic properties of bismuth(III) chloride complexes with heterocyclic thioamides

Bismuth(III) complexes of the formulae [BiCl3(MBZT)(2)] center dot H2O} (1), {[BiCl2(mu(2)-Cl)(MMI)(2)](2)center dot(CH3)(2)CO} (2), {[BiCl3(mu(2)-S-PYT)(PYT)](2)} (3) {([BiCl2(MBZIM)(4)](+))center dot 2(Cl-) center dot(H3O+)center dot 2H(2)O} (4) and [BiCl3(tHPMT)(3)] (5) (where MBZT: 2-mercaptobenzothiazole, MMI: 2-mercapto-1-methylimidazole, PYT: 2-mercaptopyridine, MBZIM: 2-mercaptobenzimidazole, tHPMT: 2-mercapto-3,4,5,6-tetrahydro-pyrimidine) are reported. The compounds were characterized by spectroscopic techniques including FT-IR, FT-Raman, UV-Vis, H-1-, C-13-NMR spectroscopies, TG-DTA, e. a, molar conductivity and by single-crystal X-ray diffraction analysis. While 1, 4 and 5 are mononuclear compounds, 2 and 3 are dinuclear complexes in which the two Bi3+ ions are bridged through Cl- and SR groups respectively. Interestingly, 3 is the first example of dinuclear Bi3+ complex containing two Bi-(mu-SR)-Bi bridges between the two metal centers formed by covalent bonds. Compounds 1-5 were evaluated for their in vitro cytotoxic activity against human adenocarcinoma cervix (HeLa) and breast (MCF-7) cells. The toxicity of 1-5 was evaluated on normal human fetal lung fibroblast cells (MRC-5). The influence of 1-5, on the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX) was determined experimentally. (C) 2017 Elsevier B.V. All rights reserved.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114Z457]; Oncology Department of Novartis Hellas S.A.C.I [81939]This research was carried out in partial fulfillment of the requirements for the master thesis of S.Y. under the supervision of I.I.O. I.I.O. and S.Y. acknowledge the financial support from The Scientific and Technological Research Council of Turkey (TUBITAK, Project No. 114Z457). The Unit of Bioactivity Testing of Xenobiotics, of the University of Ioannina-Greece, is also acknowledged for providing access to the facilities. CNB and SKH acknowledge the Oncology Department of Novartis Hellas S.A.C.I. for the financial support to CNB (project number: 81939)

Combining Azide, Carboxylate, and 2-Pyridyloximate Ligands in Transition-Metal Chemistry: Ferromagnetic Ni-5(II) Clusters with a Bowtie Skeleton

International audienceThe combined use of the anion of phenyl(2-pyridyl)ketone oxime (ppko(-)) and azides (N-3(-)) in nickel(II) carboxylate chemistry has afforded two new Ni-5(II) clusters, [Ni-5(O2CR')(2)(N-3)(4)(ppko)(4)(MeOH)(4)] [R' = H (1), Me (2)]. The structurally unprecedented {Ni-5(mu-N-3)(2)(mu(3)-N-3)(2)}(6+) cores of the two clusters are almost identical and contain the five Ni-II atoms in a bowtie topology. Two N-3(-) ions are end-on doubly bridging and the other two ions end-on triply bridging. The end-on mu(3)-N-3(-) groups link the central Ni-II atoms with the two peripheral metal ions on either side of the molecule, while the Ni center dot center dot center dot Ni bases of the triangles are each bridged by one end-on mu-N-3(-) group. Variable-temperature, solid-state direct(dc) and alternating-current (ac) magnetic susceptibility, and magnetization studies at 2.0 K were carried out on both complexes. The data indicate an overall ferromagnetic behavior and an S = 5 ground state for both compounds. The ac susceptibility studies on 1 reveal nonzero, frequency-dependent out-of-phase (chi(M)'') signals at temperatures below similar to 3:5 K; complex 2 reveals no chi(M)'' signals. However, single-crystal magnetization versus dc field scans at variable temperatures and variable sweep rates down to 0.04 K on 1 reveal no noticeable hysteresis loops, except very minor ones at 0.04 K assignable to weak intermolecular interactions propagated by nonclassical hydrogen bonds

Nickel/Lanthanide Single-Molecule Magnets: {Ni(3)Ln} "Stars" with a Ligand Derived from the Metal-Promoted Reduction of Di-2-pyridyl Ketone under Solvothermal Conditions

International audienceUnusual {Ni(3)(II)Ln(III)(mu-OR)(6)}(3+) complexes with a "star" topology have been prepared with ligands derived from the metal-promoted reduction of di-2-pyridyl ketone under solvothermal conditions; the Dy-III member shows weak single-molecule-magnet behavior

Approaches to Molecular Magnetic Materials from the Use of Cyanate Groups in Higher Oxidation State Metal Cluster Chemistry: Mn14 and Mn16

International audienceThe initial employment of cyanato groups in higher oxidation state manganese cluster chemistry, in conjunction with the gem-diolate form of di-2-pyridylketone or 2,6-diacetylpyridine dioxime chelate ligands, has afforded structurally interesting MnII/III14 and MnII/III/IV16 clusters, respectively. In both complexes, the end-on bridging cyanato groups show an obvious preference in binding through their O atom, a significantly different ligation than that for the homoatomic-type N3 ligand. The Mn14 compound shows entirely visible out-of-phase signals below 5 K and large hysteresis loops below 2 K