NiII Ions Research Articles

1,4,7‐Triazacyclononane (tacn) with N,N′‐bridging methylene‐bis(phosphinic acid) group and its complexes

AbstractA bicyclic ligand, 1,4,7‐triazacyclononane 1,4‐bridged with methylene‐bis(phosphinate) and bearing benzyl substituent on the remaining amino group, was synthesized from N‐benzyl‐tacn and CH2(PO2H2)2 by two sequential Mannich‐type reactions in a high yield. Basicity of the macrocycle is high (pK1=12.25). Complexes with CuII and NiII ions show dimeric structures in the solid state. The structures exhibit distorted octahedral environment with two ring amino groups from one molecule and two oxygen atoms of chelating bis(phosphinate) anion from the other molecule in the equatorial plane, and with the apical positions occupied by the remaining macrocycle amino group and by one of the phosphinate oxygen atoms. The metal ions in the dimers are additionally bridged by one phosphinate group. Stability of the CuII complex is more than ten orders of magnitude lower than that of the [Cu(nota)]− complex due to a different number and different nature of the pendant arms, and inappropriate arrangement of donor atoms in the ligand bicyclic structure. Rigidity of the short P−C−P chain of the geminal methylene‐bis(phosphinate) does not allow simultaneous coordination of both phosphinate groups and the ring amines to the same metal ion. The low solubility of NiII and ZnII complexes disabled determination of their stability constants.

Photocatalytic Hydrogen Evolution Coupled with Production of Highly Value-Added Organic Chemicals by a Composite Photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2.

Photocatalytic water splitting coupled with the production of highly value-added organic chemicals is of significant importance, which represents a very promising pathway for transforming green solar energy into chemical energy. Herein, we report a composite photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2 , which is highly efficient on prompting water splitting for the production of H2 in the reduction half-reaction and selective oxidation of organic molecules for the production of highly value-added organic chemicals in the oxidation half-reaction under visible light irradiation. The superior photocatalytic properties of the composite photocatalyst CdIn2 S4 @MIL-53-SO3 Ni1/2 should be ascribed to coating suspended ion catalyst (SIC), consisting of redox-active NiII ions in the anionic pores of coordination network MIL-53-SO3 - , on the surface of photoactive CdIn2 S4 , which endows photogenerated electron-hole pairs separate more efficiently for high rate production of H2 and selective production of highly value-added organic products, demonstrating great potential for practical applications.

CrIII8NiII6]n+ Heterometallic Coordination Cubes.

Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2), and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = + 0.045 cm−1. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd.

Di-chlorido-(pyridine-κN)[2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine-κ3 N 2,N 1,N 6]nickel(II).

In the title complex, [NiCl2(C5H5N)(C24H16N6)], the NiII ion is six-coordinated in a distorted octa-hedral coordination environment defined by three N atoms of the tridentate 2,3,5,6-tetra-2-pyridyl-pyrazine ligand, one N atom of the pyridine ligand and two Cl- anions, with the latter being mutually trans. The complex is disposed about a twofold rotation axis along the a axis. The complex molecules are connected in the crystal via C-H⋯Cl, C-H⋯N and π-π [closest inter-centroid separation = 3.7446 (14) Å between pyridyl rings].

A half-salamo-based pyridine-containing ligand and its novel NiII complexes including different auxiliary ligands: syntheses, structures, fluorescence properties, DFT calculations and Hirshfeld surface analysis

Three novel multinuclear NiII complexes, namely, bis{μ-2-methoxy-6-[8-(pyridin-2-yl)-3,6-dioxa-2,7-diazaocta-1,7-dien-1-yl]phenolato}bis[thiocyanatonickel(II)], [Ni2(L)2(NCS)2], 1, bis{μ-2-methoxy-6-[8-(pyridin-2-yl)-3,6-dioxa-2,7-diazaocta-1,7-dien-1-yl]phenolato}bis[azidonickel(II)], [Ni2(L)2(N3)2], 2, and catena-poly[[{2-methoxy-6-[8-(pyridin-2-yl)-3,6-dioxa-2,7-diazaocta-1,7-dien-1-yl]phenolato}nickel(II)]-μ-dicyanamidato], [Ni(L)(dca)] n , 3 {dca is dicyanamide, C2N3, and HL is 2-methoxy-6-[8-(pyridin-2-yl)-3,6-dioxa-2,7-diazaocta-1,7-dien-1-yl]phenol, C16H17N3O4}, with a half-salamo-based pyridine-containing HL ligand have been synthesized and characterized by FT–IR, UV–Vis absorption spectroscopy, X-ray crystallography, Hirshfeld surface analysis and density functional theory (DFT) calculations. The central NiII ions in complexes 1–3 are hosted in the half-salamo-based N3O-donor cavity of the organic ligand. Complex 1 is a centrosymmetric dimer and two [Ni(L)(NCS)] units form a centrosymmetric dimeric structure, which is bridged by two phenolate O atoms. The two N atoms at the axial ends are provided by two NCS− ligands. In complex 1, each NiII ion has a six-coordinated octahedral geometry. Complex 2 is similar to 1, but they differ in that the auxiliary NCS− ligand is replaced by N3 −. However, complex 3 is a one-dimensional coordination polymer constructed from [Ni(L)(dca)] units, which are connected by the auxiliary bidentate dca ligand via N-donor atoms. As with complexes 1 and 2, the NiII ion in 3 has a six-coordinated octahedral geometry.

Di-μ2-chlorido-bis-{chlorido-[2,4,6-tris-(pyridin-2-yl)-1,3,5-triazine-κ3 N 2,N 1,N 6]nickel(II)}.

In the title compound, [Ni2Cl4(C18H12N6)2], the NiII ions are hexa-coordinated in a distorted octa-hedral coordination environment defined by three N atoms of the tridentate 2,4,6-tri-2-pyridyl-1,3,5-triazine ligand and three Cl- anions in a meridional geometry. The two NiII ions are bridged by two Cl anionic ligands, thereby forming a dinuclear complex. A crystallographic centre of inversion is located at the centroid of the Ni2Cl2 ring.

{4,4'-Di-bromo-2,2'-[cyclo-hexane-1,2-diylbis(nitrilo-methanylyl-idene)]diphenolato-κ4 O,N,N',O'}nickel(II).

In the title compound, [Ni(C20H18Br2N2O2)], the NiII ion is four-coordinated in a slightly distorted square-planar coordination geometry defined by two N atoms and two O atoms of the tetra-dentate dianionic 4,4'-di-bromo-2,2'-[cyclo-hexane-1,2-diylbis(nitrilo-methanylyl-idene)]diphenolato ligand. Pairs of complex mol-ecules are assembled by inter-molecular C-H⋯O hydrogen bonds with d(C⋯O) = 3.247 (4) Å.

Synthesis, crystallographic characterization and Hirshfeld surface analysis of metal complexes of conformationally constrained β-amino acid, 2-(1-aminocyclohexyl)acetic acid with CoII, NiII, CuII and ZnII ions

2-(1-aminocyclohexyl)acetic acid (β 3,3-Ac6cH) is selected as a lead compound to synthesize a new series of mononuclear transition metal complexes of the type [MII-(Κ2-O,N- β 3,3-Ac6c)2(H2O)2] (M = CoIIC1, NiIIC2, CuIIC3, and ZnIIC4. All the complexes C1-C4 have been suitably characterized by relevant spectroscopic techniques, viz. NMR (1H, 13C, DEPT 135), UV–visible, IR, and HRMS (for C1) spectroscopies. These complexes displayed ν(M-N) and ν(M-O) bands in the region of 417–448 and 395–410 cm−1, respectively having maximum absorbance in the UV region. A clear blue shifts up to 20–51 nm of n→π* electronic transition band (360–390 nm), compared to its position in β3,3-Ac6cH, clearly demonstrates the participation of amine/carboxylate moieties in the complex formation. In addition, complexes C1, C2, and C3 exhibit weak d-d transition bands in the visible region at 560 nm, 630 nm, and 602 nm, respectively. The X-ray analysis of both complexes C3 and C4 confirms the distorted octahedral geometry around Cu and Zn centers. In both complexes, the equatorial positions are occupied by N, O donor sites of coordinated ligands, while the axial positions are occupied by oxygen atoms of the two water molecules. The molecules of C3 and C4 are predominantly stabilized by several intermolecular bifurcated non-conventional hydrogen bonding interactions, viz. NH…O, and OH…O in the solid state. Notably, the space fill model demonstrates the formation of rectangular voids in the molecular packing of C3, showing 2D sheet like architecture in ab-plane. The Hirshfeld surface and subsequent fingerprint plots were calculated to quantify the intermolecular contacts present within the crystal structure of compounds C3 and C4.

In vitro and in silico assessment of antitumor properties and biomolecular binding studies for two new complexes based on NiII bearing k2N,S-donor ligands

This work deals with two new molecule-based materials, namely NiII-complexes of general formulae [Ni(L1)2] (Ni1) and [Ni(L2)2] (Ni2), where L1 = trans-cinnamaldehyde-N(4)-methyl thiosemicarbazone and L2 = trans-cinnamaldehyde-N(4)-ethyl thiosemicarbazone, as potential antitumor agents. Both compounds were characterized by elemental analysis, molar conductivity and spectroscopic techniques (FTIR and NMR). Their molecular structures were obtained by single-crystal X-ray diffraction analysis. Each one crystallizes in a monoclinic space group P 21/c, also the asymmetric unit comprises of one NiII ion located on an inversion centre and one anionic ligand, which acts as a κ2N,S-donor affording a five-membered metallaring. The compounds were screened against two selected tumour cell lines (MCF-7 and A549) and non-tumour fibroblasts cell line (MRC-5) via MTT assays. In both tumour cells, all compounds exhibited higher cytotoxicity than the control drug (cisplatin). The IC50 values ranges of 3.70 – 41.37 μM and 1.06 – 14.91 μM were found for MCF-7 and A549, respectively. Importantly, all of them were less toxicity than cisplatin in MRC-5 with SI values ranged at 11.80 – 86.60. The red blood cell (RBC) assay revealed Ni2 as non-toxic due to its reduced haemolytic effect (0‐–9% at 1‐–10 μM). The DNA binding was investigated through a combination of spectrophotometric absorption and emission titrations, electrophoresis, and circular dichroism experiments. As a result, these metal complexes were not able to strongly binding to DNA (Kb values ~104 mol L‐−1) but suggesting groove-binding interactions. The scavenging ability of them towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical was also evaluated in this work, but no important antioxidant behaviour was detected. Further, the interaction of Ni1 and Ni2 to human serum albumin (HSA) was explored by quenching of tryptophan emission, warfarin competitive assay, and molecular docking protocols. The HSA binding analyses indicated good affinity of both complexes to Sudlow site I (Kb values ⁓103 mol L−1).

Formation of Defect-Dicubane-Type NiII 2LnIII 2 (Ln = Tb, Er) Clusters: Crystal Structures and Modeling of the Magnetic Properties.

In the field of molecular nanoclusters, cubane and defect-dicubane, or butterfly structures, are typical examples of tetranuclear metal core architectures. In this work, a halogenated and anionic Schiff-base ligand (L2–) is utilized as it is predisposed to chelate within a cluster core to both 3d and 4f metal ions, in different binding configurations (H2L = 4-chloro-2-(2-hydroxy-3-methoxybenzyliden amino)phenol). The phenolate oxygen atoms of the deprotonated ligand can act in μ-O and μ3-O bridging binding modes for the intramolecular assembly of metal ions. Based on that, two tetranuclear and isostructural compounds [Ni2Tb2(L)4(NO3)2(DMF)2]·2CH3CN (1) and [Ni2Er2(L)4(NO3)2(DMF)2]·0.5CH3CN (2) were synthesized and structurally characterized. Magnetic susceptibility and magnetization data indicate the occurrence of dominant intramolecular ferromagnetic interactions between the spin centers. Particular emphasis is given to the theoretical description of the magnetic behavior, taking into account the Ln–Ni and Ni–Ni coupling paths and the magnetic anisotropy of the LnIII and NiII ions. The study is distinguished for its discussion of two distinct models, whereby model A relies on the uniaxial B20 Stevens term describing the lanthanide anisotropy and model B is based on point-charge model calculations. Importantly, the physical meaning of the obtained parameters for both models was critically scrutinized.

Transition Metal Ion‐Directed Coordination Polymers with Mixed Ligands: Synthesis, Structure, and Photocatalytic Activity for Hydrogen Production and Rhodamine B Degradation

Three mixed‐ligand transition metal coordination polymers with the formula of {[CuI2CuII(tpt)2(L)]·15H2O}n (1) and {[M2(H2O)5(tpt)(L)]·6H2O}n [M = Ni for 2 and Co for 3; tpt = 2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine and L = 3,3'‐disulfonyl‐4,4'‐biphenyldicarboxylate] were hydrothermally synthesized by varying the cheap paramagnetic metal ions and used as photocatalysts for hydrogen evolution from water splitting and rhodamine B (RhB) degradation. Single‐crystal structural determinations reveal that 1 is a robust pillared‐layer framework with unusual 72‐membered {Cu6(tpt)6} macrocycle‐based layers supported by tetratopic L4– connectors. Both 2 and 3 are isostructural (4 4) sheets with octahedral NiII and CoII ions extended by ditopic L4– and tpt linkages, in which the third pyridyl group of tpt is capped by pentahydrated metal ions. Due to the narrowed bandgap and good charge transport of the mixed‐valence CuI/II centers, 1 exhibits improved dual‐functional catalytic activities than 2 and 3 with the visible‐light‐driven hydrogen evolution rate and RhB degradation efficiency up to 588 μmol·g–1·h–1 and 72 % after 180‐minute irradiation. These interesting results indicate the importance of the metal ions and the dimensionality of the coordination polymers on the activity of the non‐Pt coordination polymer photocatalytic systems.

Tailoring Crystal Facets of Metal-Organic Layers to Enhance Photocatalytic Activity for CO2 Reduction.

It is common that different crystal facets in metal and metal oxide nanocrystals display different catalytic performances, whereas such phenomena have been rarely documented in metal-organic frameworks (MOFs). Herein, we demonstrate for the first time that a nickel metal-organic layer (MOL) exposing rich (100) crystal facets (Ni-MOL-100) shows a much higher photocatalytic CO2 -to-CO activity than the one exposing rich (010) crystal facets (Ni-MOL-010) and its bulky counterpart (bulky Ni-MOF), with a catalytic activity up to 2.5 and 4.6 times more active than Ni-MOL-010 and bulky Ni-MOF, respectively. Theoretical studies reveal that the two coordinatively unsaturated NiII ions with a close distance of 3.50 Å on the surface of Ni-MOL-100 enables synergistic catalysis, leading to more favorable energetics in CO2 reduction than that of Ni-MOL-010.

Tailoring Crystal Facets of Metal–Organic Layers to Enhance Photocatalytic Activity for CO2 Reduction

AbstractIt is common that different crystal facets in metal and metal oxide nanocrystals display different catalytic performances, whereas such phenomena have been rarely documented in metal–organic frameworks (MOFs). Herein, we demonstrate for the first time that a nickel metal–organic layer (MOL) exposing rich (100) crystal facets (Ni‐MOL‐100) shows a much higher photocatalytic CO2‐to‐CO activity than the one exposing rich (010) crystal facets (Ni‐MOL‐010) and its bulky counterpart (bulky Ni‐MOF), with a catalytic activity up to 2.5 and 4.6 times more active than Ni‐MOL‐010 and bulky Ni‐MOF, respectively. Theoretical studies reveal that the two coordinatively unsaturated NiII ions with a close distance of 3.50 Å on the surface of Ni‐MOL‐100 enables synergistic catalysis, leading to more favorable energetics in CO2 reduction than that of Ni‐MOL‐010.

Influence of structural variation of salamo‐based ligand on supramolecular architectures, Hirshfeld analyses, and fluorescence properties of new tetranuclear NiII complexes

Two new tetranuclear NiII complexes, [Ni4(L1)2(N3)4(MeOH)2]·CH3COCH3 (1) and [Ni4(L2)2(N3)4(MeOH)2]·4CH3COCH3 (2), were synthesized using NiCl2·6H2O, NaN3, and asymmetric salamo‐based ligands H2L1 and H2L2, respectively. The structural characterization was made by elemental analyses, infrared (IR) and ultraviolet‐visible (UV‐vis) spectra, and X‐ray diffraction analyses. The results of X‐ray diffraction analyses show that the NiII atoms in complexes 1 and 2 are distorted octahedral geometries. Interestingly, the degree of distortion of the ligands in complexes 1 and 2 is different, which indicates that the interaction of NiII ions on different ligands is different. Meanwhile, the investigation of molecular packing by employing the Hirshfeld surface analysis exhibits that the percentages of C–H/H–C, O–H/H–O, and H–H/H–H contacts of the complex 1 (or 2) are calculated to be 17.7%, 7.9%, and 53.7% (or 18.8%, 13.8%, and 52.5%), respectively, where the H–H/H–H contacts have the characteristics of strong contacts whereas the O–H/H–O hydrogen bonds are considerably weak, and the studies on fluorescence properties further confirm the NiII atoms have different binding abilities to the different ligands.

Supramolecular isomerism in two nickel(II) coordination polymers constructed with the flexible 2-carboxyphenoxyacetate linker: Syntheses, structure analyses and magnetic properties

Two binary nickel (II) supramolecular isomers, namely 1D-Ni and 2D-Ni with the same formula [Ni(2-cpa)2(H2O)]n (2-H2cpa ​= ​2-carboxyphenoxyacetic acid), have been prepared by different synthetic methods and systematically characterized. Single-crystal X-ray diffraction analysis shows that the central NiII ion of 1D-Ni is located in a deformed square–pyramid bonded by one water and two 2-cpa anionic ligands. Each 2-cpa exhibits tetradentate bridging chelate-μ2 coordination mode and joins neighbouring NiII ions to form a 1-D zigzag chain structure. While for 2D-Ni, the NiII center is in a distorted octahedral geometry surrounded by one water and three 2-cpa. The 2-cpa displays pentadentate double bridging chelate-μ3 coordination pattern and links adjacent NiII ions to generate a corrugated (4,4)-connected layer. The magnetic measurements indicated that there are both weak ferromagnetic coupling between neighbouring NiII ions in 1D-Ni and 2D-Ni. In addition, the driving force for the formation of two isomers have been carefully analyzed and discussed.

Synthesis and crystal structure of a heterobimetallic nickel-manganese 12-metallacrown-4 methanol disolvate monohydrate compound.

The synthesis and crystal structure of the title compound [systematic name: di-μ-acetato-tetra-kis-(μ4-N,2-dioxido-benzene-1-carboximidato)hexa-methano-ltetra-manganese(III)nickel(II) methanol disolvate monohydrate], [Mn4Ni(C7H4NO3)4(C2H3O2)2(CH4O)6]·2CH4O·H2O or Ni(OAc)2[12-MCMn(III)N(shi)-4](CH3OH)6·2CH3OH·H2O, where MC is metallacrown, -OAc is acetate, and shi3- is salicyl-hydroximate, are reported. The macrocyclic metallacrown is positioned on an inversion center located on the NiII ion that resides in the central MC cavity. The macrocycle consists of an MnIII-N-O repeat unit that recurs four times to generate an overall square-shaped mol-ecule. Both the NiII and MnIII ions are six-coordinate with an octa-hedral geometry. In addition, the MnIII ions possess an elongated Jahn-Teller distortion along the z-axis of the coordination environment. The inter-stitial water mol-ecule is slightly offset from and disordered about an inversion center.

Dinickel(II) complexes with pyridine-substituted bis(triazolylmethyl)amine ligands: Structures and magnetic properties

The coordination behavior of the newly prepared bis(triazolylmethyl)amine-type ligands bis[(1-R-1H-1,2,3-triazol-4-yl)methyl]amine [R = CH2Ph (L1), CH2-2-pyridyl (L2)] and 1-(1-benzyl-1H-1,2,3-triazol-4-yl)-N-((1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)methanamine (L3) toward NiII ions was investigated. The reaction of NiCl2·6H2O with the benzyl-substituted bis(triazolylmethyl)amine ligand L1 afforded the mononuclear NiII complex Ni(L1)2Cl2 (1). On the other hand, dinuclear NiII complexes, [Ni2(L2)2Cl2]Cl2 (2) and [Ni2(L3)2Cl2]Cl2 (3), were obtained when NiCl2·6H2O was reacted with the pyridine-substituted ligands L2 and L3, respectively. Single-crystal X-ray analysis revealed that the two octahedral NiII centers in 2 and 3 are bridged by two triazole rings through nitrogen donors to generate the dinuclear complexes with a syn arrangement. Meanwhile, treatment of Ni(NO3)2 with L2 afforded the related dinickel(II) complex [Ni2(L2)2(NO3)2](NO3)2 (2′), in which two non-bridging triazole rings and two nitrate ions are positioned in an anti arrangement. Complexes 2 and 3 showed antiferromagnetic coupling between the two NiII centers (S = 1), with J values following the trend: 2′ > 2 > 3.

Replacement of the Cobalt Center of Vitamin B12 by Nickel: Nibalamin and Nibyric Acid Prepared from Metal-Free B12 Ligands Hydrogenobalamin and Hydrogenobyric Acid.

The (formal) replacement of Co in cobalamin (Cbl) by NiII generates nibalamin (Nibl), a new transition‐metal analogue of vitamin B12. Described here is Nibl, synthesized by incorporation of a NiII ion into the metal‐free B12 ligand hydrogenobalamin (Hbl), itself prepared from hydrogenobyric acid (Hby). The related NiII corrin nibyric acid (Niby) was similarly synthesized from Hby, the metal‐free cobyric acid ligand. The solution structures of Hbl, and Niby and Nibl, were characterized by spectroscopic studies. Hbl features two inner protons bound at N2 and N4 of the corrin ligand, as discovered in Hby. X‐ray analysis of Niby shows the structural adaptation of the corrin ligand to NiII ions and the coordination behavior of NiII. The diamagnetic Niby and Nibl, and corresponding isoelectronic CoI corrins, were deduced to be isostructural. Nibl is a structural mimic of four‐coordinate base‐off Cbls, as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase.

Replacement of the Cobalt Center of Vitamin B12 by Nickel: Nibalamin and Nibyric Acid Prepared from Metal‐Free B12 Ligands Hydrogenobalamin and Hydrogenobyric Acid

AbstractThe (formal) replacement of Co in cobalamin (Cbl) by NiII generates nibalamin (Nibl), a new transition‐metal analogue of vitamin B12. Described here is Nibl, synthesized by incorporation of a NiII ion into the metal‐free B12 ligand hydrogenobalamin (Hbl), itself prepared from hydrogenobyric acid (Hby). The related NiII corrin nibyric acid (Niby) was similarly synthesized from Hby, the metal‐free cobyric acid ligand. The solution structures of Hbl, and Niby and Nibl, were characterized by spectroscopic studies. Hbl features two inner protons bound at N2 and N4 of the corrin ligand, as discovered in Hby. X‐ray analysis of Niby shows the structural adaptation of the corrin ligand to NiII ions and the coordination behavior of NiII. The diamagnetic Niby and Nibl, and corresponding isoelectronic CoI corrins, were deduced to be isostructural. Nibl is a structural mimic of four‐coordinate base‐off Cbls, as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase.

Dinickel(Ii) Complexes with Pyridine-Substituted Bis(Triazolylmethyl)Amine Ligands: Structures and Magnetic Properties

Coordination behavior of newly prepared bis(triazolylmethyl)amine-type ligands, bis[(1-R-1H-1,2,3-triazol-4-yl)methyl]amine [R = CH2Ph (L1), CH2-2-pyridyl (L2)] and 1-(1-Benzyl-1H-1,2,3-triazol-4-yl)-N-((1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)methanamine (L3), toward NiII ions was investigated. The reaction of NiCl2·6H2O with the benzyl-substituted bis(triazolylmethyl)amine ligand L1 afforded the mononuclear NiII complex Ni(L1)2Cl2 (1). On the other hand, the dinuclear NiII complexes, [Ni2(L2)2Cl2]Cl2 (2) and [Ni2(L3)2Cl2]Cl2 (3), were obtained when NiCl2·6H2O was reacted with the pyridine-substituted ligands, L2 and L3, respectively. Single-crystal X-ray analysis revealed that two octahedral NiII centers in 2 and 3 are bridged by two triazole rings through nitrogen donors to generate the dinuclear complexes with a syn arrangement. Meanwhile, treatment of Ni(NO3)2 with L2 afforded the related dinickel(II) complex, [Ni2(L2)2(NO3)2](NO3)2 (2'), in which two non-bridging triazole rings and two nitrate ions were positioned in an anti arrangement. Complexes 2 and 3 showed the antiferromagnetic coupling between two NiII centers (S = 1), with J values following the trend: 2' > 2 > 3.