NiII Centers Research Articles

Rare examples of diphenoxido-bridged trinuclear NiII2FeIII complexes with a reduced salen type Schiff base ligand: Structures and magnetic properties

Three new trinuclear hetero-metallic complexes, [(NiLR)2Fe(N3)3] (1), [(NiLR(H2O))2Fe(C6H5CH2CO2)2]·(HSO4) (2) and [(NiLR(H2O))2Fe(C6H5CO2)2]·(HSO4)·(H2O)·(CH2Cl2) (3) have been synthesized using [NiLR] as a “metalloligand” (where H2LR=N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic study. In the angular trinuclear units of 1, the two terminals [NiLR] coordinate through double phenoxido bridges to the central FeIII ion which is penta-coordinated having terminally coordinated azide ion. The two terminal NiII centers are connected to each other and also to neighbouring units through μ1,3-azido bridges to form an alternating chain. On the other hand, complexes, 2 and 3 are linear discrete trinuclear species [NiII–FeIII–NiII] in which two terminal octahedral [NiLR] units coordinate to the central octahedral FeIII ion, located on a crystallographic centre of symmetry, through a μ2-phenoxido oxygen atom and a bridging carboxylato ion. Variable temperature magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions in 1 mediated through the phenoxido bridges (J1=−33.2cm−1,) and μ1,3-N3 single bridges (J2=−19.9cm−1 and J3=−16.7cm−1). On the other hand, compounds 2 and 3 show ferromagnetic coupling interactions mediated through the double phenoxido bridges with J values of +4.9 and +3.0cm−1 for 2 and 3, respectively.

Synergistic treatment of triple-negative breast cancer by doxorubicin and thioridazine and its nano-formulation

Three new trinuclear hetero-metallic complexes, [(NiLR)2Fe(N3)3] (1), [(NiLR(H2O))2Fe(C6H5CH2CO2)2]·(HSO4) (2) and [(NiLR(H2O))2Fe(C6H5CO2)2]·(HSO4)·(H2O)·(CH2Cl2) (3) have been synthesized using [NiLR] as a “metalloligand” (where H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic study. In the angular trinuclear units of 1, the two terminals [NiLR] coordinate through double phenoxido bridges to the central FeIII ion which is penta-coordinated having terminally coordinated azide ion. The two terminal NiII centers are connected to each other and also to neighbouring units through μ1,3-azido bridges to form an alternating chain. On the other hand, complexes, 2 and 3 are linear discrete trinuclear species [NiII–FeIII–NiII] in which two terminal octahedral [NiLR] units coordinate to the central octahedral FeIII ion, located on a crystallographic centre of symmetry, through a μ2-phenoxido oxygen atom and a bridging carboxylato ion. Variable temperature magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions in 1 mediated through the phenoxido bridges (J1 = −33.2 cm−1,) and μ1,3-N3 single bridges (J2 = −19.9 cm−1 and J3 = −16.7 cm−1). On the other hand, compounds 2 and 3 show ferromagnetic coupling interactions mediated through the double phenoxido bridges with J values of +4.9 and +3.0 cm−1 for 2 and 3, respectively.

Syntheses, structures and characterization of isomorphous CoII and NiII coordination polymers based on 2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole and benzene-1,4-dicarboxylate.

Careful choice of the organic ligands is one of the most important parameters in the rational design and synthesis of coordination polymers. Aromatic polycarboxylates have been widely used in the preparation of metal-organic polymers since they can utilize various coordination modes to form diverse structures and can act as hydrogen-bond acceptors and donors in the assembly of supramolecular structures. Nitrogen-heterocyclic organic compounds have also been used extensively as ligands for the construction of polymers with interesting structures. In the polymers catena-poly[[[diaquabis{2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole-κN3}cobalt(II)]-μ2-benzene-1,4-dicarboxylato-κ2O1:O4] dihydrate], {[Co(C8H4O4)(C12H11N4)2(H2O)2]·2H2O}n, (I), and catena-poly[[[diaquabis{2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole-κN3}nickel(II)]-μ2-benzene-1,4-dicarboxylato-κ2O1:O4] dihydrate], {[Ni(C8H4O4)(C12H11N4)2(H2O)2]·2H2O}n, (II), the CoII or NiII ion lies on an inversion centre and exhibits a slightly distorted octahedral coordination geometry, coordinated by two N atoms from two imidazole rings and four O atoms from two monodentate carboxylate groups and two water molecules. The dicarboxylate ligands bridge metal ions forming a polymeric chain. The 2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole ligands coordinate to the CoII or NiII centres in monodentate modes through an imidazole N atom and are pendant on opposite sides of the main chain. The two structures are isomorphous. In the crystal, the one-dimensional chains are further connected through O-H...O, O-H...N and N-H...O hydrogen bonds, leading to a three-dimensional supramolecular architecture. In addition, the IR spectroscopic properties, PXRD patterns, thermogravimetric behaviours and fluorescence properties of both polymers have been investigated.

Stable NiII Porphyrin meso-Oxy Radical with a Quartet Ground State.

10,15,20-Tris(pentafluorophenyl)-substituted NiII -porphyrin meso-oxy radical bearing two coordinating pyridines was synthesized as a stable radical with a quartet ground state (S=3/2). X-ray structural analysis revealed that the NiII porphyrin moiety is fairly planar and the Ni-N bond lengths are considerably longer, indicating the high-spin state of the NiII center. The radical exhibited a quartet ground state, indicating the ferromagnetic interaction between the high-spin NiII center (S=1) and the porphyrin meso-oxy radical (S=1/2).

Diphenylphosphine-Oxide-Fused and Diphenylphosphine-Fused Porphyrins: Synthesis, Tunable Electronic Properties, and Formation of Cofacial Dimers.

Diphenylphosphine-oxide-fused NiII porphyrin 8 was synthesized from 3,5,7-trichloroporphyrin 5 via a reaction sequence of nucleophilic aromatic substitution with lithium diphenylphosphide, oxidation with H2 O2 , and palladium-catalyzed intramolecular cyclization. Reduction of 8 with HSiCl3 gave diphenylphosphine-fused NiII porphyrin 9. The embedded P=O and P moieties serve as a strong electron-accepting and electron-donating group to perturb the optical and electrochemical properties of the NiII porphyrin. NiII porphyrin 9 is diamagnetic with a low-spin NiII center in solution but becomes paramagnetic with a five-coordinated NiII center with high-spin (S=1) state in the solid state. Diphenylphosphine-oxide-fused ZnII porphyrin 10 was also synthesized and shown to form a face-to-face dimer with mutual O-Zn bonds in the crystal and in nonpolar and moderately polar solvents. The dimerization of 10 in CDCl3 has been revealed to be an entropy-driven process with a large entropy gain (ΔSD =207 J K-1 mol-1 ).

Synthesis and Speciation-Dependent Properties of a Multimetallic Model Complex of NiSOD That Exhibits Unique Hydrogen-Bonding

The complex Na3[{NiII(nmp)}3S3BTAalk)] (1) (nmp2- = deprotonated form of N-(2-mercaptoethyl)picolinamide; H3S3BTAalk = N1,N3,N5-tris(2-mercaptoethyl)benzene-1,3,5-tricarboxamide, where H = dissociable protons), supported by the thiolate-benzenetricarboxamide scaffold (S3BTAalk), has been synthesized as a trimetallic model of nickel-containing superoxide dismutase (NiSOD). X-ray absorption spectroscopy (XAS) and 1H NMR measurements on 1 indicate that the NiII centers are square-planar with N2S2 coordination, and Ni-N and Ni-S distances of 1.95 and 2.16 Å, respectively. Additional evidence from IR indicates the presence of H-bonds in 1 from the approximately -200 cm-1 shift in νNH from free ligand. The presence of H-bonds allows for speciation that is temperature-, concentration-, and solvent-dependent. In unbuffered water and at low temperature, a dimeric complex (1A; λ = 410 nm) that aggregates through intermolecular NH···O═C bonds of BTA units is observed. Dissolution of 1 in pH 7.4 buffer or in unbuffered water at temperatures above 50 °C results in monomeric complex (1M; λ = 367 nm) linked through intramolecular NH···S bonds. DFT computations indicate a low energy barrier between 1A and 1M with nearly identical frontier MOs and Ni-ligand metrics. Notably, 1A and 1M exhibit remarkable stability in protic solvents such as MeOH and H2O, in stark contrast to monometallic [NiII(nmp)(SR)]- complexes. The reactivity of 1 with excess O2, H2O2, and O2•- is species-dependent. IR and UV-vis reveal that 1A in MeOH reacts with excess O2 to yield an S-bound sulfinate, but does not react with O2•-. In contrast, 1M is stable to O2 in pH 7.4 buffer, but reacts with O2•- to yield a putative [NiII(nmp)(O2)]- complex from release of the BTA-thiolate based on EPR.

Solution and solid state structures and magnetism of a series of linear trinuclear compounds with a hexacoordinate LnIII and two terminal NiII centers.

Reported are the syntheses, structures and magnetic properties, also by NMR spectroscopy in solution, of a series of 13 linear trinuclear 3d-4f compounds with a lanthanide(iii) surrounded by two NiII ions, NiLnIII, where the central LnIII is hexacoordinate. For three of the crystal structures, an additional H2O molecule is coordinated to the central LnIII ion, leading to a monocapped trigonal prismatic structure. However, NMR spectroscopy indicates that in solution, these complexes also have a hexacoordinate LnIII center. The solution magnetic anisotropies, determined by NMR spectroscopy, indicate that the axial components of the anisotropies are relatively small and that the DyIII derivative might therefore not exhibit single molecule magnetism. The axial anisotropies determined by NMR spectroscopy are in good agreement with the expectations based on the distorted trigonal prismatic ligand field.

Flexible Metal-Porphyrin Dimers (M=MnIII Cl, CoII , NiII , CuII ): Synthesis, Spectroscopy, Electrochemistry, Spectroelectrochemistry, and Theoretical Calculations.

Four metalloporphyrin dimers linked by bridging amide-bonded xanthene moieties and that contain either MnIII , CoII , NiII , or CuII metal centers were synthesized. Various spectroscopic, electrochemical, and spectroelectrochemical methods were used to study trends in their properties. Their electronic structure and optical properties were analyzed through a comparison of the electronic absorption and magnetic circular dichroism (MCD) spectral data with the results of time-dependent (TD)-DFT calculations.

Synthesis and characterization of a tetranickel complex supported by a dithiolate framework with pendant ether moieties

We report here the synthesis of a novel dithiolate ligand framework with pendant ether groups. Metallation reactions were performed with nickel(II) precursors, in the presence of base, leading to a tetranuclear nickel(II) species, as evidenced by single crystal X-ray diffraction studies. A C2v symmetric structure is observed, with the NiII centers in a square arrangement. Each NiII center is coordinated by four bridging thiolates.

Binuclear cyanido complexes containing [Pt(CN)4]2− building block: Synthesis, crystal structures, magnetic properties and anticancer activities

Five new complexes of composition [Ni(N-bishydeten)Pt(CN)4] (1), [Ni(N-bishydeten)2][Pt(CN)4] (2), [Cu(N-bishydeten)Pt(CN)4] (3), [Cu(N-bishydeten)2][Pt(CN)4] (4) and [Cd(N-bishydeten)2][Pt(CN)4] (5) {N-bishydeten=N,N-bis(2-hydroxyethyl)-ethylenediamine} have been obtained and characterized by IR and EPR spectroscopies, elemental and thermal analysis and magnetic measurements. X-ray studies of 2 and 3 exhibited different structures and two different coordination modes of N-bishydeten ancillary ligand with a ratio of M:L. While N-bishydeten acts as a tetradentate with N, N′, O and O′ atoms in a molar ratio of 1:1 formed 2,2-CT-type zigzag chain for 3, it behaves tridentate ligand by ending up with six coordinated NiII center in a complex salt by using 1:2M ratio for 2. None of the 1 and 3 complexes produced in this study showed sufficient anticancer activity but all did exhibit apoptotic properties and one of them also performed low cytotoxic activity against cell tested.

A Ni11 Coordination Cluster from the Use of the Di-2-Pyridyl Ketone/Acetate Ligand Combination: Synthetic, Structural and Magnetic Studies

The combined use of di-2-pyridyl ketone, (py)2CO, and acetates (MeCO2−) in nickel(II) chemistry in H2O-MeCN under basic conditions (Et3N) afforded the coordination cluster [Ni11(OH)6(O2CMe)12{(py)2C(OH)(O)}4(H2O)2] (1) in 80% yield, where (py)2C(OH)(O)− is the monoanion of the gem-diol form of (py)2CO. The complex contains a novel core topology. The core of 1 comprises a central non-linear {Ni3(μ2-OH)4}2+ subunit which is connected to two cubane {Ni4(OH)(μ3-OR)2(μ3-OR′)}4+ subunits [RO− = (py)2C(OH)(O)− and R′O− = MeCO2−] via the OH− groups of the former which become μ3. The linkage of the Ni3 subunit to each Ni4 subunit is completed by two η1:η1:μ2 and one η1:η3:μ4 MeCO2− groups. Peripheral ligation is provided by two terminal monodentate MeCO2− and two terminal aqua ligands. The (py)2C(OH)(O)− ligands adopt the η1:η1:η3:μ3 coordination mode. From the twelve MeCO2− ligands, two are η1, two η1:η3:μ4 and eight adopt the syn, syn η1:η1:μ2 coordination mode; four of the latter bridge NiII centers at opposite faces of the cubane subunits. Complex 1 is the largest nickel(II)/(py)2CO-based ligand coordination cluster discovered to date and has an extremely rare nuclearity (Ni11) in the cluster chemistry of nickel(II). Variable-temperature, solid state dc susceptibility, and variable-field magnetization studies at low temperatures were carried out on complex 1. The study of the data reveals an S = 3 ground state, which has been well rationalized in terms of known magnetostructural correlations and the structural features of 1. An attempt has also been made to interpret the magnetic properties of the undecanuclear cluster in a quantitative manner using four exchange interaction parameters and the obtained J values are discussed. The role of H2O in the solvent medium that led to 1, and the high nickel(II) and acetate to di-2-pyridyl ketone reaction ratio employed for its preparation, on the nuclearity and identity of the cluster are critically analyzed.

Redox Non‐Innocence of Nitrosobenzene at Nickel

AbstractNitrosobenzene (PhNO) serves as a stable analogue of nitroxyl (HNO), a biologically relevant, redox‐active nitric oxide derivative. Capture of nitrosobenzene at the electron‐deficient β‐diketiminato nickel(I) complex [iPr2NNF6]Ni results in reduction of the PhNO ligand to a (PhNO)./− species coordinated to a square planar NiII center in [iPr2NNF6]Ni(η2‐ONPh). Ligand centered reduction leads to the (PhNO)2− moiety bound to NiII supported by XAS studies. Systematic investigation of structure–reactivity patterns of (PhNO)./− and (PhNO)2− ligands reveals parallels with superoxo (O2)./− and peroxo (O2)2− ligands, respectively, and forecasts reactivity patterns of the more transient HNO ligand.

Two coordination polymers containing the dicyanamide ligand: Synthesis, crystal structures, and HFEPR studies

Two new compounds [Ni(dca)2(dmdpy)] (1) and [Zn(dca)2(dmdpy)] (2), (dca=dicyanamide and dmdpy=5,5′-dimethyl-2,2′-dipyridine) were synthesized and characterized by single crystal X-ray diffraction, FTIR and thermal analysis. In both compounds, the dmdpy ligand adopts a bidentate chelating coordination mode while dca anions act in a μ1,5 bridging fashion. In 1, the NiII centers lie on a distorted octahedral geometry, whereas in 2 the ZnII geometry is distorted square pyramidal. In compounds 1 and 2, dca ligands connect the metal sites giving rise to 2D and 1D coordination polymers, respectively. The magnetic properties of 1 were studied by magnetic susceptibility and high field/frequency electron paramagnetic resonance (HFEPR) measurements.

Syntheses, Crystal Structures, and Magnetic Properties of Two Mononuclear Nickel‐Nitronyl Nitroxide Radical Compounds

AbstractTwo nickel(II) complexes were synthesized and structurally as well as magnetically characterized by using two positional isomeric nitronyl nitroxide radical ligands and H3cda as co‐ligand: [Ni(NIToPy)(cda)]H2O·CH3OH (1) and [Ni(IM4Py)2(cda)H2O] (2) [NIToPy = 2‐(3′‐pyridinyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl‐3‐oxide; IM4Py = 2‐(4′‐pyridinyl)‐4,4,5,5‐tetramethylimidazoline‐l‐oxyl; H3cda = 4‐hydroxypyridine‐2,6‐dicarboxylic acid]. Single‐crystal structures analyses show that both complexes have similar mononuclear structures, in which the central NiII ions are hexacoordinated with a distorted octahedral arrangement. The magnetic properties of 1 and 2 were studied, and antiferromagnetic interactions between NiII ion and radicals are observed.

Preparation, First Structure Analysis, and Magnetism of the Long‐Known Nickel Benzoate Trihydrate – A Linear Ni···Ni···Ni Polymer and Its Parallels with the Active Site of Urease

AbstractNickel benzoate trihydrate (1) has been prepared in single‐crystalline form by the reaction of nickel carbonate with benzoic acid in boiling aqueous solution. Its crystal structure comprises positively charged [Ni(Bz)(H2O)2]nn+ chains, benzoate anions, and one independent water molecule of solvation. The hexacoordinate NiII centers in the chains are triply bridged by one syn‐syn carboxylato and two aqua bridges, and adjacent chains are linked by O–H···O hydrogen bonds [O···O distances are in the range 2.647(3)–2.684(3) Å] through solvate water molecules and benzoate anions. Thermal analysis revealed that 1 is stable up to 100 °C; further heating led to full dehydration accompanied by an additional decomposition reaction, as characterized by IR analysis of the intermediates. The geometrical features of the Ni centers have been compared with similar features at the active sites of urease. The effective magnetic moment per formula unit µeff has a value of 3.17µB at room temperature and upon cooling reaches a maximum value of 12.39µB at T = 4.6 K, which indicates ferromagnetic coupling between the nearest NiII atoms [3.0671(1) Å] within the chains; at lower temperatures this is counteracted by zero‐field splitting.

Influence of the Homopolar Dihydrogen Bonding C-H⋅⋅⋅H-C on Coordination Geometry: Experimental and Theoretical Studies.

The reaction of the N-thiophosphorylated thiourea (HOCH2 )(Me)2 CNHC(S)NHP(S)(OiPr)2 (HL), deprotonated by the thiophosphorylamide group, with NiCl2 leads to green needles of the pseudotetrahedral complex [Ni(L-1,5-S,S')2 ]⋅0.5 (n-C6 H14 ) or pale green blocks of the trans square-planar complex trans-[Ni(L-1,5-S,S')2 ]. The former complex is stabilized by homopolar dihydrogen C-H⋅⋅⋅H-C interactions formed by n-hexane solvent molecules with the [Ni(L-1,5-S,S')2 ] unit. Furthermore, the dispersion-dominated C-H⋅⋅⋅ H-C interactions are, together with other noncovalent interactions (C-H⋅⋅⋅N, C-H⋅⋅⋅Ni, C-H⋅⋅⋅S), responsible for pseudotetrahedral coordination around the Ni(II) center in [Ni(L-1,5-S,S')2 ]⋅0.5 (n-C6 H14 ).

Synthesis, Crystal Structures, and Magnetic Properties of Heterodimetallic Ru III –3d Coordination Compounds Based on a Meridional Tricyanoruthenium(III) Building Block

The synthesis, crystal structures, and magnetic properties of three cyano-bridged heterodimetallic compounds prepared from the paramagnetic RuIII building block mer-[RuIII(CN-sap)(CN)3]2– (1) are described. Complex 1 reacts with [MnII(LN5)(Cl)(H2O)]Cl and [MnII(bipy)2(Cl)2] (bipy = bipyridine) to produce the 1D zigzag chain {[RuIII(CN-sap)(CN)](μ-CN)2[MnII(LN5)]·3MeOH}n {2; LN5 = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, CN-sapH2 = 2-hydroxy-N-(2-hydroxyphenyl)benzimidoyl cyanide} and the octanuclear compound {[RuIII(CN-sap)(CN)](μ-CN)2[MnII(bipy)(MeOH)][RuIII(CN-sap)](μ-CN)3[MnII(bipy)2]}2·8MeOH (3), respectively. The MnII centers have a pentagonal-bipyramidal environment in 2 and a distorted octahedral environment in 3. Complex 1 reacts with [NiII(cyclen)(Cl)2] (cyclen = 1,4,7,10-tetraazacyclododecane) in MeOH to produce the molecular square {[RuIII(CN-sap)(CN)](μ-CN)2[NiII(cyclen)]}2·8MeOH (4). Compounds 2 and 3 exhibit antiferromagnetic coupling between the RuIII and MnII centers, whereas 4 exhibits ferromagnetic coupling between the RuIII and NiII centers through the cyano bridges.

Structures and Magnetic Properties of Bis(μ‐phenoxido), Bis(μ‐phenoxido)‐μ‐carboxylato and Bis(μ‐phenoxido)bis(μ‐carboxylato) FeIIINiII Compounds – Magnetostructural Correlations

AbstractThis report describes the syntheses, characterization, crystal structures and magnetic properties of five dinuclear FeIIINiII compounds derived from two Robson‐type tetraiminodiphenol macrocyclic ligands H2L1 and H2L2, which are the [2+2] condensation products of 4‐ethyl‐2,6‐diformylphenol and 1,3‐diaminopropane (for H2L1) or 2,2‐dimethyl‐1,3‐diaminopropane (for H2L2). The compositions of the compounds are [FeIII(N3)2L1NiII(H2O)2](ClO4) (1), [FeIII(benzoato)L1NiII(H2O)(μ1,3‐benzoato)](ClO4) (2), [FeIII(benzoato)L2NiII(H2O)(μ1,3‐benzoato)](ClO4) (3), [FeIIIL2NiII(μ1,3‐acetato)2](ClO4)·H2O (4) and [FeIIIL2NiII(μ1,3‐propionato)2](ClO4)·H2O (5). The bridging moieties between the two metal ions and the azido and carboxylato moieties in these compounds are of the following types: (1) In 1, the bridging moiety is a bis(μ‐phenoxido) ligand, and two azido ligands are monodentate to the FeIII centre; (2) In 2 and 3, the bridging moiety is a bis(μ‐phenoxido)‐μ1,3‐benzoato ligand, and the second benzoato ligand is monodentate to the FeIII centre; (3) In 4 and 5, the bridging moiety is a bis(μ‐phenoxido)bis(μ1,3‐acetato/propionato) ligand. Variable‐temperature and variable‐field magnetic data reveal ferromagnetic interactions in 2–5 and an antiferromagnetic interaction in 1 with J values of –9.22 cm–1 for 1, 0.50 cm–1 for 2, 5.65 cm–1 for 3, 13.00 cm–1 for 4 and 14.57 cm–1 for 5. An excellent magnetostructural correlation and interesting structural aspects regarding the bond lengths to the FeIII or NiII centres in some structures have been obtained.

Bi-Nuclear Metal Complexes of 2,6-Bis(1,4,7-triazacyclonon-1-yl-methylene)pyridine with Zinc(II), Copper(II), and Nickel(II)

The coordination chemistry of 2,6-bis(1,4,7-triazacyclonon-1-ylmethyl)pyridine (Lpyx, 1) has been investigated and shown to yield bi-nuclear metal complexes in the presence of zinc(ii), copper(ii), or nickel(ii) ions. The reaction of (Lpyx)·7HCl (2) with Zn(NO3)2 gave the monomeric [Zn2(μ-Cl)2(Lpyx)(H2O)](ClO4)2 (3) in which the ligand encapsulates a Zn2(μ-Cl)2 moiety. Similar treatment of 2 with Cu(NO3)2 gave a bi-nuclear complex cation which exists as a 1 : 1 co-crystal {[Cu(Cl)(Lpyx)Cu(μ-Cl)(Cl)](BF4)(H2O)}2 and {[Cu(Cl)(Lpyx)Cu(μ-Cl)(H2O)](BF4)2(H2O)}2 (4) with two discrete CuII centres bridged by the Lpyx ligand and dimerised through an unsymmetrical Cu2(μ-Cl)2 interaction. Similarly, reaction of 2 with Ni(NO3)2 also gave a dimeric complex {[Ni(Cl)(μ-Cl)(Lpyx)Ni(NO3)(H2O)](PF6)}2 (5) containing two discrete NiII centres with dimerisation occurring through a symmetrical Ni2(μ-Cl)2 interaction. In all cases, the Lpyx ligand binding is unsymmetrical between the two metal centres being tridentate to one and tetradentate to the other through an additional coordination of the pyridyl linker.

Manganese(II), nickel(II), and cadmium(II) coordination polymers with tetrafluoroterephthalate: syntheses, crystal structures, and luminescence properties

Three new coordination polymers, [Mn(BDC-F4)(DMF)2(H2O)2]n (1), [Ni(BDC-F4)(DMF)(EtOH)]n (2), and [Cd(BDC-F4)(DMF)(EtOH)]n (3), have been synthesized by assembling transition metal salts with the rigid ligand tetrafluoroterephthalic acid (H2BDC-F4) in mixed EtOH/DMF solvent at pH ca. 2. For complex 1, the octahedral coordination geometry of the MnII center is provided by two oxygen atoms from two dianionic BDC-F4 ligands, two DMF ligands and two aqua ligands, giving a 1-D linear chain array. For complex 2, the NiII center is coordinated by two dianionic BDC-F4 ligands, two EtOH ligands and two DMF ligands, resulting in a 1-D chain structure. For complex 3, the CdII center is coordinated by four dianionic BDC-F4 ligands, one EtOH ligand and one DMF ligand, generating a 2-D layered structure. The results suggest that both the metal and the solution pH play an important role in the formation of the complexes. The spectroscopic, thermal, and luminescence properties of the complexes have been investigated.