Acetato Bridges Research Articles

Synthesis and Characterization of New Copper(II) Coordination Compounds with Methylammonium Cations

We synthesized four new copper(II) complexes with acetato and chlorido ligands and methylammonium (MA), dimethylammonium (DMA), and tetramethylammonium (TMA) counterions: (MA)4[Cu2Ac4Cl2]Cl2·2H2O (1), (DMA)2[Cu2Ac4Cl2] (2), (DMA)4[Cu2Ac4Cl2]Cl2·2H2O (3), and (TMA)5[Cu2Ac4Cl]Cl4·4H2O (4). All compounds were characterized by single-crystal X-ray diffraction, magnetic measurements, FTIR spectroscopy, and thermogravimetric analysis. Complexes 1, 2, and 3 consist of a dinuclear coordination anion [Cu2(Ac)4Cl2]2− with bridging acetato ligands arranged in a paddle-wheel conformation and square-pyramidal coordination around Cu(II) atoms, while the coordination anion in compound 4 is a polymeric chain, parallel to the c axis, with Cu2(Ac)4 units connected through bridging chlorido ligands. Magnetic measurements carried out between 2 K and 300 K indicate strong antiferromagnetic interactions between Cu(II) ions. The effective magnetic moments range from 1.94 μB to 2.21 μB, exceeding the spin-only value for Cu(II) ions (μeff=1.73 μB) and suggesting significant orbital contributions to the magnetic moment. Thermogravimetric analysis of all complexes showed a multistep decomposition behavior yielding elemental copper as the final product.

An oxo‐acetato‐bridged trinuclear cobalt(III) cluster‐persuaded cobalt oxide active electrocatalyst for efficient hydrogen evolution activity

This study presents the synthesis and electrocatalytic performance of the cobalt(III) complex [Co3(μ1,1,1‐O)(μ1,3‐CH3CO2)(L)3]2(DMF)3 (Cotri), featuring a double deprotonated (N,O)‐donor ligand (L2‐), where the protonated form of it (H2L) is 2,2′‐(hydrazine‐1,2‐diylidenebis(ethan‐1‐yl‐1‐ylidene))diphenol. The X‐ray structure reveals a trinuclear cobalt cluster formed with three cobalt(III) centers interlinking through oxido (μ1,1,1‐O) and acetato (μ1,3‐O2CCH3) bridges in coupling with bis‐congregator‐type chelating ligands. Cotri adopts cobalt centers of octahedral and trigonal bipyramidal coordination geometries and bears a dominant Co(2)…H(DMF) agostic interactions appraised by lattice dimethyl formamide (DMF) molecules. Further, Cotri shows promising heterogeneous electrocatalytic hydrogen evolution activity in 1 M KOH, with an overpotential of 441 mV to achieve 10 mA/cm2 current density. Tafel slope analysis suggests the Volmer–Heyrovsky step as the rate‐determining step. The number of active sites and TOF for Cotri were estimated at 4.010 × 10−8 mol and 0.2467 s−1, respectively, ensuring its excellent hydrogen generation activity. Stability assessments through controlled potential electrolysis (CPE) and cyclic voltammetry (CV) for multiple cycles addressed the transformation of Cotri to Co2O3 nanoparticles, which turned out to be a more active Co2O3 electrocatalyst. The morphology and particle size of the in situ developed Co2O3 active catalyst under the electrochemical conditions attributes to the superior hydrogen evolution activity.

From field-induced to zero-field SMMs associated with open/closed structures of bis(ZnDy) tetranuclear complexes: a combined magnetic, theoretical and optical study.

We have prepared a bis(compartmental) Mannich base ligand H4L (1,4,8,11-tetraaza-1,4,8,11-tetrakis(2-hydroxy-3-methoxy-5-methylbenzyl)cyclotetradecane) specifically designed to obtain bis(TMIILnIII) tetranuclear complexes (TM = transition metal). In this regard, we have succeeded in obtaining three new complexes of the formula [Zn2(μ-L)(μ-OAc)Dy2(NO3)2]·[Zn2(μ-L)(μ-OAc)Dy2(NO3)(OAc)]·4CHCl3·2MeOH (1) and [TM2(μ-H2L)2(μ-succinate)Ln2(NO3)2] (NO3)2·2H2O·6MeOH (TMII = Zn, LnIII = Dy (2); TMII = Co, LnIII = Dy (3)). Compound 1 contains two different bis(ZnDy) tetranuclear molecules that cocrystallize in the structure, in which acetato bridging ligands connect the ZnII and DyIII ions within each ZnDy subunit. This compound does not exhibit slow magnetic relaxation at zero field, but it is activated in the presence of an applied dc magnetic field and/or by Dy/Y magnetic dilution, showing two relaxation processes corresponding to each of the two different bis(ZnDy) units found in the structure. As revealed by the theoretical calculations, magnetic relaxation in 1 is single-ion in origin and takes place through the first excited state of each DyIII ion. When using the succinato dicarboxylate bridging ligand instead of acetate, compounds 2 and 3 were serendipitously formed, which have a closed structure with the succinate anion bridging two ZnDy subunits belonging to two different ligands. It should be noted that only compound 2 exhibits slow relaxation of magnetization in the absence of an external magnetic field. According to experimental and theoretical data, 2 relaxes through the second excited Kramers doublet (Ueff = 342 K). In contrast, 3 displays field-induced SMM behaviour (Ueff = 203 K). However, the Co/Zn diluted version of this compound 3Zn shows slow relaxation at zero field (Ueff = 347 K). Ab initio theoretical calculations clearly show that the weak ferromagnetic coupling between CoII and DyIII ions is at the origin of the lack of slow relaxation of this compound at zero field. Compound 2 and its diluted analogues 2Y and 3Zn show hysteresis loops at very low temperature, thus confirming their SMM behaviour. Finally, compounds 1 and 2 show DyIII based emission even at room temperature that, in the case of 2, allows us to extract the splitting of the ground 6H15/2 term, which matches reasonably well with theoretical calculations.

Synthesis, Crystal Structures and Urease Inhibition of Zinc Complexes Derived from 4-Chloro-2-(((2-(pyrrolidin-1-yl)ethyl)imino)methyl)phenol.

Three new zinc(II) complexes, [Zn3(μ2-η1:η1-OAc)2(μ2-η2:η0-OAc)2L2] (1), [Zn3(μ2-η1:η1-OAc)2(μ1,1-N3)(N3)L2] (2), [Zn2(μ1,3-N3)(N3)(H2O)L2] (3), with the Schiff base ligand 4-chloro-2-(((2-(pyrrolidin-1-yl)ethyl)imino)methyl)phenol (HL) have been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopic studies. Crystal structures of the complexes were confirmed by single crystal X-ray diffraction. Complex 1 is a bidentate acetato, monoatomic bridging acetato, and phenolato co-bridged trinuclear zinc compound. The Zn atoms are in octahedral and square pyramidal coordination. Complex 2 is a bidentate acetato, end-on azido, and phenolato co-bridged trinuclear zinc compound. The Zn atoms are in trigonal bipyramidal and square pyramidal coordination. Complex 3 is an end-to-end azido bridged dinuclear zinc compound. The Zn atoms are in square pyramidal and trigonal bipyramidal coordination. The Schiff base ligands in the complexes coordinate to the Zn atoms through the phenolate oxygen, imino nitrogen and pyrrolidine nitrogen. The complexes have interesting inhibitory activity on Jack bean urease, with IC50 values of 7.1-15.3 μmol·L-1.

Synthesis, structure and properties of new triiron(III) complexes: Phosphodiester cleavage and antioxidant activity

This paper describes the synthesis, structural and spectroscopic characterizations of two new trinuclear iron(III) complexes: [Fe3(LS)(μ –OH)2(μ -OAc)2]ClO4 (CS) and [Fe3(LSe)(μ –OH)2(μ -OAc)2]ClO4 (CSe) with two new phenol-based ligands containing chalcogen atoms (S or Se) in pendant arms. Both iron complexes were characterized using the following techniques: X-ray crystallography, elemental analysis, IR, Mossbauer and UV–vis spectroscopies, conductimetric analysis and mass spectrometry. The crystal structures of the complexes reveal that their coordination center is formed by three linearly arranged iron atoms, joined by μ -hydroxo, μ -phenoxo and μ -acetato bridges. The hydrolytic activity in the phosphate diester cleavage of CSe and CS was investigated using 2,4-BDNPP as a substrate, and applying the Michaelis-Menten approach, giving the kinetic parameters (CSe/CS): kcat (s−1) = 3.81 × 10-3/2.32 × 10-3 and a catalytic efficiency of E = kcat/ KM, (L/mol s−1) = 1.83/3.18. The complexes and ligands also showed antioxidant activity.

A trinuclear nickel(II) Schiff base complex with phenoxido- and acetato-bridges: combined experimental and theoretical magneto-structural correlation.

We describe the synthesis and characterization of a new trinuclear Ni(ii) Schiff base complex of formula [Ni3(L)2(NCS)2(OAc)2(CH3OH)2] (1) where HL is the 1 : 1 condensation product of 2-picolylamine and o-vanillin. The crystal structure of complex 1 shows that the two terminal Ni(ii) ions are connected to the central one through a phenoxido- and a syn-syn acetato bridge, giving rise to a very bent configuration in the Ni3-core. Magnetic susceptibility measurements show the presence of a weak antiferromagnetic coupling with J = -3.22(2) cm-1. We also report a magneto-structural correlation, performed with all the magnetically characterized Ni(ii) trimers with similar bridges, showing a linear dependence between the J value and the dihedral angle (θ) between the planes containing the Ni-O-Ni and the carboxylate bridges. The super-exchange interaction is investigated by extensive density functional calculations within the broken symmetry approximation which show good agreement with the experimental data. The analysis of the spin density distribution and the shape of the magnetically active single occupied molecular orbitals (SOMO) provide a mechanism of exchange coupling through the bridging groups.

Trinuclear nickel(II) amino acid Schiff base complex containing phenolato and acetato bridges: Structural and functional resemblance of urease

A novel phenolato and acetato bridged trinuclear Ni(II) complex [Ni3L2] was synthesized by the reaction between the amino acid Schiff base, N-o-vanillylidene-l-histidine(L) and Ni(OAc)2·2H2O. Single crystal X-ray analysis reveals that the trinuclear structure of Ni3L2 is built by linking two terminal NiN2O4 cores with one NiO6 centre core (NiN2O4⋯NiO6⋯NiN2O4) and each Ni(II) ion exists in an octahedral environment. Variable-temperature magnetic susceptibility data represent the antiferromagnetic interactions of the Ni3L2 mediated by a single Ni-O-Ni bridge. The bond length and bond angles around each terminal nickel centre match the nickel centre in urease enzyme of native bacteria Klebsiella aerogenes, Bacillus pasteurii and Helicobacter pylori. The catalytic activity of Ni3L2 on the hydrolysis of urea into ammonia and carbon dioxide was established by the absorption spectral method. The urea binding propensity of the nickel complex Ni3L2 was compared with jack bean urease by using molecular docking studies.

Formation of a copper–copper bond in coordination of a cyclotriphosphazene ligand toward Cu(II): Structural, spectral and docking studies

Two cyclotriphosphazene compounds, [HMPAP]2[SO4]·2CH3OH (1), MPAP: 2,2,4,4,6,6-hexakis(2-methyl-1λ4-pyridin-1-yl)-1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine and [Cu(μ-OAc)2(MPAP)]2 (2), were prepared and identified by elemental analysis, FT-IR, Raman spectroscopy and single-crystal X-ray diffraction. In the crystal structure of 1, one nitrogen atom of the cyclotriphosphazene ring has been protonated. The copper complex (2) is binuclear formed by four bridging acetato ligands containing one Cu–Cu bond in the center of the complex. Each copper atom has a Cu(O4NCu) environment with octahedral geometry which is distorted owing to the Jahn-Teller effect. In the crystal network of the compounds, in addition to hydrogen bonds and hydrogen bond motifs (only in 1), π-π stacking interactions between phenyl rings further stabilize the crystal network. Based on the docking studies on the MPAP and its copper complex (2) with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II, B-DNA), the binding ability of the MPAP ligand toward biomacromolecules is significantly higher than the copper complex and doxorubicin drug and can be considered a biologically active compound.

2D-Coordination polymer containing lead(II) in a hemidirected PbO4S3 environment formed by molecular breaking of the 1,3-oxathiolane ligand

Abstract A new 1,3-oxathiolane-based ligand, 2-(1,3-oxathiolan-2-yl)pyridine, was prepared and its coordination to lead(II) was investigated. Experiments revealed a ligand-breaking reaction during the complexation process, which leads to the formation of a 2D-coordination polymer of lead(II), [Pb(μ 3-HME)(μ-OAc)] n ; H2ME: 2-mercaptoethanol. The compounds have been characterized by elemental analysis, FT-IR, 1H NMR spectroscopy and single-crystal X-ray diffraction. X-ray analysis revealed a 2D-coordination polymer extending via acetato bridges. The lead(II) center adopts a rare PbO4S3-distorted pentagonal bipyramidal geometry with a hemidirected arrangement. Upon coordination, the thiol group of the H2ME ligand is deprotonated to coordinate as an anionic ligand. The network extends in sheets in the crystallographic ab plane via Pb–S–Pb and Pb–O–Pb bridges, aided by O–H⋯O hydrogen bonds.

The crystal structures of the ligand N-(quinolin-8-yl)pyrazine-2-carboxamide and of a tetra-nuclear copper(II) complex.

The title tridentate ligand, C14H10N4O, N-(quinolin-8-yl)pyrazine-2-carboxamide (HL1), crystallizes with three independent mol-ecules (A, B and C) in the asymmetric unit. All three mol-ecules are relatively planar (r.m.s. deviations are 0.068, 0.055 and 0.06 Å, respectively), with the NH H atom forming three-centered (bifurcated) intra-molecular N-H⋯N hydrogen bonds in each mol-ecule. There is also an intra-molecular C-H⋯O contact present in each mol-ecule, involving the benzene ring of the quinoline unit and the amide carboxamide O atom. In the crystal, the three mol-ecules stack in columns with the various mol-ecules being linked by offset π-π inter-actions [inter-centroid distances vary from 3.367 (5) to 3.589 (5) Å], forming layers parallel to the ab plane. The title complex, [Cu4(C42H44N8O16)]·2CH3OH, {hexa-μ-acetato-1:2κ2 O:O';2:3κ8 O:O';3:4κ2 O:O'-di-methanol-1κO,2κO-bis-[N-(quinolin-8-yl)pyrazine-2-carboxamide]-1κ3 N,N',N'';4κ3 N,N',N''-tetra-copper(II) methanol disolvate} (I), was obtained by the reaction of HL1 with Cu(CH3CO2)2. It consists of a tetra-nuclear complex with a central tetra-kis-(μ-acetato)-dicopper paddle-wheel moiety linked on either side via bridging acetato ions to a mononuclear copper(II)-(L1) complex; it crystallizes as a methanol disolvate. The complex possesses inversion symmetry, being located about a center of symmetry situated at the mid-point of the Cu⋯Cu bond of the paddle-wheel moiety. In the crystal, the complex mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains along the [01] direction, which are linked by offset π-π inter-actions [inter-centroid distance = 3.7367 (11) Å] and C-H⋯O hydrogen bonds, leading to the formation of a supra-molecular framework.

Tetranuclear Hetro-Metal [MnIII2NiII2] Complexes Involving Defective Double-Cubane Structure: Synthesis, Crystal Structures, and Magnetic Properties

Tetranuclear hetero-metal MnIII2NiII2 complexes, [Mn2Ni2(L)4(OAc)2] (1) and [Mn2Ni2(L)4(NO3)2] (2) [H2L = N-(2-hydroxymethylphenyl)-5,6-benzosalicylideneimine], have been synthesized and characterized by X-ray crystal structure analyses, infrared spectra, and elemental analyses. The structure analyses revealed that the complexes have a defective double-cubane metal core connected by μ3-alkoxo bridges. Complexes consist of two bis-μ-alkoxo bridged MnIIINiII heteronuclear units making a dimer-of-dimers structure. The double-cubane cores are significantly distorted due to an effect of syn–syn mode acetato or nitrato bridges. Magnetic measurements indicate that weak antiferromagnetic interactions (Mn-Ni = −0.66 ~ −4.19 cm–1) are dominant in the hetero-metal core.

Effect of crystal packing and coordinated solvent molecules on metal-ligand bond distances in linear trinuclear nickel compounds with bridging acetato and Schiff base ligands

Abstract A combined experimental and theoretical study on the molecular structure of linear trinuclear nickel compounds of general formula [Ni3(μ-Zsaltn)2(μ-AcO)2(S)2] (Z = H, 1S, and Br, 2S, where S identifies coordinated solvent molecules) is here presented. In these complexes the three metal ions are linked together by bridging acetato ions and tetradentate Schiff base ligands, these last derived from the condensation of 1,3-diaminopropane with two equivalents of 5-Z-salicylaldehyde. Two solvent molecules S can also interact with the terminal nickel ions to complete an octahedral coordination environment. We report the synthesis of [Ni3(μ-Brsaltn)2(μ-AcO)2] (2), and its crystal structure with two coordinated dimethylformamide molecules, [Ni3(μ-Brsaltn)2(μ-AcO)2(DMF)2] (2DMF). Its comparison with the crystal structure of 2 without solvent, together with the series of compounds 1, 1DMF, 1MeOH, 1DMSO, 1Py and 1H2O (MeOH = methanol, DMSO = dimethylsulfoxide, Py = pyridine) available in the literature, allows recognising modification in Ni O and Ni N coordination bond lengths and peculiar intermolecular contacts between neighbour molecules. In order to discern among the contribution of solvent molecules, crystal packing and substituent Z (H or Br) on bond distances (and angles), we performed a systematic theoretical study on four representative derivatives, namely 1, 1DFM, 2 and 2DMF, with the M06 functional and a careful choice of the best basis set. The results indicate that, while the major modulating factor is the presence or absence of the sixth solvent molecule to the peripheral nickel(II) ion, even if less strongly coordinated with Ni O/N bond distances > 2.15 A, π-π stacking interactions and C H⋯π and/or C Br⋯π non-bonded interactions affect the coordination geometry in a significant way.

Organic-inorganic hybrid materials from divalent metal cations and expanded N,N′-donor linkers

Abstract The rod-shaped linker (E,E)-N,N′-(3,3′-dimethyl-4,4′-biphenyldiyl)bis[1-(3-pyridinyl)methanimine] (L) is exploited for the first time in the synthesis of extended structures. Four new coordination polymers of composition {[ZnL(OAc)2]·EtOH}n (1), {[CdL(OAc)2]·MeOH}n (2), {[Cu2L(OAc)4]·CH2Cl2}n (3) and [MnL(N3)2]n (4) have been structurally characterized. The metal cations and the anionic ancillary ligands play pivotal roles for the topology of these compounds. In the crystalline reaction products of Zn(II), Cd(II) and Cu(II) acetate with the organic linker, the acetate anions connects two neighboring cations to dinuclear [M2(OAc)4] subunits. These secondary building units are further crosslinked by the N,N′-donor ligand, either perpendicular to the acetato bridges, leading to a ladder-like ribbon for 1 and 2, or in the direction of the metal···metal separation, resulting in a simple chain in the case of 3. Instead of dinuclear secondary building units, a different topology results from reaction of the N,N′ linker with Mn(ClO4)2 in the presence of azide anions: 1,3 bridging by the N3 − groups leads to infinite chains. These are crosslinked by L in perpendicular direction, and the layer structure 4 is obtained. Natural bond orbital (NBO) analyses revealed information on the basis of orbital interactions about the coordination environments of the metal ions. Thermogravimetric measurements indicate the highest thermal stability for 2. Strong antiferromagnetic coupling within the dinuclear subunits of 3 is observed as a consequence of superexchange via the acetato bridges.

Hexaaza‐dithia Macrocycles Containing Pendant Methoxyethyl Groups: Synthesis and Characterization of Mono and Dinuclear Nickel Complexes

AbstractThe deprotection of two bicyclic hexaaza‐dithioether macrocycles 1 and 2 containing four (or six) N‐bound 2‐methoxyethyl substituents was achieved in good yields utilizing Li or Na/naphthalene in THF as the reagent. The ability of the resulting hexaaza‐dithiophenolate macrocycles (H2L4 and H2L5) to act as mono‐ and dinucleating ligands is also demonstrated. Three nickel complexes, namely [Ni(H2L4)][BPh4]2 (3), [Ni2(L4)(μ‐OAc)][BPh4] (4), and [Ni2(L5)(μ‐OAc)][BPh4] (5), were obtained and characterized by elemental analyses, ESI mass spectrometry, IR and UV/Vis spectroscopy, and in case of 3 and 4 also by X‐ray crystallography. The five‐coordinate nickel atom in complex 3 was found to interact only weakly with one of the four 2‐methoxyethyl groups. The nickel atoms in dinuclear 4 and 5 are coordinatively saturated by the nitrogen and sulfur donor atoms of the macrocycle and the oxygen atoms of the bridging acetato coligands, such that the methoxyethyl substituents function only as dangling groups.

Establishing the Family of Diruthenium Water Oxidation Catalysts Based on the Bis(bipyridyl)pyrazolate Ligand System.

A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bis(tridentate) ligand for the formation of efficient diruthenium water oxidation catalysts (J. Am. Chem. Soc. 2014, 136, 24-27). Now, detailed protocols for the synthesis of a whole family of such dinuclear ruthenium complexes [{Ru(pyR(2))2}2(μ-(R1)bbp)(X,Y)](2+) based on the bis(bipyridyl)pyrazolate scaffold are reported. The isolation of a synthetic key intermediate allowed the straightforward introduction of different pyridines as axial ligands. Thereby, a set of complexes with different substituents at the pyrazolate backbone (R(1) = Br, H, Me), different pyridines as axial ligand (R(2) = H, NMe2, SO3), and different (non)bridging units in the in,in-position (X,Y = Cl, H2O, OAc) has been prepared and thoroughly characterized. Complexes of the type [{Ru(pyR(2))2}2(μ-(R1)bbp)(μ-OAc)](2+), with an exogenous acetato bridge, have been used as catalyst precursors in catalytic water oxidation experiments with a sacrificial oxidant. The effect of substitution on the pyrazole core of the (R1)bbp(-) ligand as well as on the pyridine ligands on both electrochemistry and catalytic activity has been systematically investigated. The catalyst stability, reflected by the turnover number, is crucially determined by the substituent at the pyrazolate ligand (R(1) = Me > H > Br). In contrast, the axial pyridine ligands modulate the rate of the catalytic process, expressed by the initial turnover frequency (R(2) = H > NMe2H(+)).

Modulating Relaxation Dynamics of Dy2 Compounds through Carboxylate Coordination Modes

AbstractThe reaction of the rigid polydentate Schiff‐base H3L with different dysprosium carboxylates afforded two novel centrosymmetrical dinuclear DyIII compounds, [Dy2(HL)2(CH3COO)2(DMF)2] (1) and [Dy2(HL)2(PhCOO)2(DMF)2]·4DMF (2) with differing carboxylate groups. The two differing carboxylate groups affect the magnetic interaction and/or local anisotropy of the Dy ion, and therefore we have two compounds showing dissimilar magnetic behaviour. The acetato bridging groups with a syn‐syn η1:η1:μ2 mode in compound 1 lead to the disappearance of slow magnetic relaxation under zero dc field. Nevertheless, typical SMM behaviour is observed for compound 2 with η2‐chelating benzoate ligands.

Tetranuclear Nickel(II) and Cobalt(II) Complexes with 3,5-Dimethyl-1-pyrazolylmethanolato and Acetato Bridges Having a Cubane Core

There have been considerable interest in the coordination chemistry of metal complexes with pyrazole and their derivatives owing to diverse coordination modes and relevance to a biological-active metal center with imidazole-like ligands.1–8 Recently, we studied metal complexes with a multidentate ligand, N,N,N¢,N¢-tetrakis(3,5-dimethyl-1-pyrazolyl)methyl-1,4phenylenediamine (tpmp), having the 1,4-phenylenediamine moiety, and isolated a dinuclear cobalt complex from a reaction of cobalt(II) chloride and tpmp consisting of two tetrahedral cobalt(II) atoms with two pyrazolato-nitrogen atoms of tpmp and two chloride atoms.6 In this study, we tried to extend this work to reactions with other metal salts, such as cobalt(II) acetate and nickel(II) acetate. We found totally different products with 3,5-dimethyl-1-pyrazolyl)methanolato (dmpm–), as shown in Fig. 1, [M4(dmpm)4(O2CCH3)4]·2CH3CN (M = Ni and Co). Here, we report on the crystal structures of these complexes. The ligand tpmp was synthesized by a method described in the literature.8 [Ni4(dmpm)4(O2CCH3)4]·2CH3CN To a solution of tpmp (54 mg, 0.1 mmol) in 10 cm3 of acetonitrile was added 25 mg (0.1 mmol) of nickel(II) acetate tetrahydrate. The reaction mixture was stirred overnight at room temperature. The resulting cleargreen solution was left for several days to yield green crystals. These crystals were collected, washed by acetonitrile, and dried under a vacuum. Yield, 35 mg. Anal. Found: C, 41.42; H, 5.27; N, 13.49%. Calcd for C36H54N10Ni4O12: C, 41.04; H, 5.17; N, Tetranuclear Nickel(II) and Cobalt(II) Complexes with 3,5-Dimethyl-1pyrazolylmethanolato and Acetato Bridges Having a Cubane Core

Crystal Structure and <sup>1</sup>H NMR Spectral Property of a Lantern-Type Diruthenium(II,III) Complex with One Formamidinato and Three Acetato Bridges

Crystal Structure and <sup>1</sup>H NMR Spectral Property of a Lantern-Type Diruthenium(II,III) Complex with One Formamidinato and Three Acetato Bridges

Syntheses, Structures, and Magnetic Properties of Acetato- and Diphenolato-Bridged 3d–4f Binuclear Complexes [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (M = ZnII, CuII, NiII, CoII; Ln = LaIII, GdIII, TbIII, DyIII; 3-MeOsaltn = N,N′-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato; ac = Acetato; hfac = Hexafluoroacetylacetonato; x = 0 or 1)

A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (x = 0 for M = Cu(II), Zn(II); x = 1 for M = Co(II), Ni(II); Ln = Gd(III), Tb(III), Dy(III), La(III)), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged M(II)-Ln(III) binuclear structure. The Cu(II)-Ln(III) and Zn(II)-Ln(III) complexes are crystallized in an isomorphous triclinic space group P1, where the Cu(II) or Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The Co(II)-Ln(III) and Ni(II)-Ln(III) complexes are crystallized in an isomorphous monoclinic space group P2(1)/c, where the Co(II) or Ni(II) ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each Ln(III) ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of "ligand-complex" M(3-MeOsaltn), four oxygen atoms of two hfac(-), and one oxygen atom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the Ln(III) (Tb(III), Dy(III)) and to a lesser extent the M(II) (Ni(II), Co(II)) components, the magnetic interaction between M(II) and Ln(III) ions were investigated by an empirical approach based on a comparison of the magnetic properties of the M(II)-Ln(III), Zn(II)-Ln(III), and M(II)-La(III) complexes. The differences of χ(M)T and M(H) values for the M(II)-Ln(III), Zn(II)-Ln(III) and those for the M(II)-La(III) complexes, that is, Δ(T) = (χ(M)T)(MLn) - (χ(M)T)(ZnLn) - (χ(M)T)(MLa) = J(MLn)(T) and Δ(H) = M(MLn)(H) - M(ZnLn)(H) - M(MLa)(H) = J(MLn)(H), give the information of 3d-4f magnetic interaction. The magnetic interactions are ferromagnetic if M(II) = (Cu(II), Ni(II), and Co(II)) and Ln = (Gd(III), Tb(III), and Dy(III)). The magnitudes of the ferromagnetic interaction, J(MLn)(T) and J(MLn)(H), are in the order Cu(II)-Gd(III) > Cu(II)-Dy(III) > Cu(II)-Tb(III), while those are in the order of M(II)-Gd(III) ≈ M(II)-Tb(III) > M(II)-Dy(III) for M(II) = Ni(II) and Co(II). Alternating current (ac) susceptibility measurements demonstrated that the Ni(II)-Tb(III) and Co(II)-Tb(III) complexes showed out-of-phase signal with frequency-dependence and the Ni(II)-Dy(III) and Co(II)-Dy(III) complexes showed small frequency-dependence. The energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the Ni(II)-Tb(III) and Co(II)-Tb(III) complexes, respectively, under a dc bias field of 1000 Oe.

Structural, magnetic, and 1H NMR spectral study on lantern-type cis- and trans-diruthenium(II,III) complexes with two formamidinato and two acetato bridges

Abstract Lantern-type dinuclear complexes, cis-[Ru2(4-Me-pf)2(O2CMe)2Cl] and trans-[Ru2(2,6-Et2-pf)2(O2CMe)2Cl] (4-Me-pf− = N,N′-bis(4-methylphenyl)formamidinate ion and 2,6-Et2-pf− = N,N′-bis(2,6-diethylphenyl)formamidinate ion), were prepared and characterized. The dinuclear structures with cis- and trans-arrangements of the bridging ligands were confirmed by the X-ray crystal structures as well as 1H NMR spectra (298 K) in CD2Cl2, where the proton signals were observed at widely spread positions δ = − 80 to 25 ppm. Variable-temperature magnetic moments (2–300 K) showed the existence of three unpaired electrons in dinuclear units with large D values (65 cm− 1 for cis-Ru2II,III and 90 cm− 1 for trans-Ru2II,III).