MII Ions Research Articles

Solvothermal Syntheses and Structural Characterisation of Three Isostructural 3D Metal‐Malate Coordination Polymers: {[M(C4H4O5)(H2O)]·H2O}n (M = CoII, NiII, CoII/NiII)

AbstractThree isostructural coordination polymers with the general formula {[M(C4H4O5)(H2O)]·H2O}n [M = CoII (1), NiII (2) and 1/3CoII + 2/3NiII (3), C4H4O5 = Hmal2−, malate dianion] have been designed and synthesised via solvothermal routes. In these compounds, the malate acts as the unique quinque‐dentate ligand with all five oxygen atoms participating in the coordination. The MII ions are interconnected via α‐ and β‐carboxyl groups from the malate ligands to generate zigzag chains and planes which are further linked together by the β‐carboxyl groups leading to the 3D open frameworks. Variable temperature magnetic susceptibility measurements indicate the occurrence of antiferromagnetic (1), ferromagnetic (2) and ferrimagnetic (3) interactions between the MII ions mediated by the skew‐skew carboxylate bridges. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Discrete Dinuclear Complexes and Two‐Dimensional Architectures from Bridging Polynitrile and Bipyrimidine (bpym) Ligands: Syntheses, Structures and Magnetic Properties of [M2(bpym)(dcne)4(H2O)2] (M = MnII, CoII) and [M2(bpym)(dcne)4(H2O)4]·2H2O (M = FeII, CuII) (dcne− = [(CN)2CC(O)OEt)]−)

AbstractOne‐pot reactions in aqueous solutions of the polynitrile anion dcne− {2,2‐dicyano‐1‐ethoxyethenolate = [(CN)2CC(O)OEt)]−] with the MII ions (M = Mn, Fe, Co, Cu) in the presence of bpym (2,2′‐bipyrimidine) afford the first mixed dcne/bpym compounds [M2(bpym)(dcne)4(H2O)2] (1: M = Mn; 2: M = Co) and [M2(bpym)(dcne)4(H2O)4]·2H2O (3: M = Fe; 4: M = Cu). The new compounds have been characterized by IR spectroscopy and X‐ray crystallography. Compounds 1 and 2 are isostructural, with each metal ion being located in an MN5O pseudo‐octahedral environment with three N atoms coming from three dcne− ligands, two nitrogen atoms from bpym and one oxygen atom from a water molecule. The extended structures of 1 and 2 are best described as dcne‐bridged zigzag chains of MII ions running along the [100] direction; connections of these chains in the [010] direction, by the bis(chelating) bpym ligand, afford 2D structures. Compounds 3 and 4 are isostructural, and consist of discrete dinuclear units involving MN4O2 octahedrally coordinated MII ions bridged by bis(bidentate) 2,2′‐bipyrimidine and terminal dcne ligands. Magnetic measurements for the 2D compounds 1 and 2 exhibit maxima in the χm vs. T plots (at about 4.5 K for 1 and about 20 K for 2) which are characteristic of weak antiferromagnetic exchange interactions between the high‐spin metal centres. While the dinuclear iron complex 3 presents a similar behaviour (maximum in χm vs. T plot at 12 K), the antiferromagnetic exchange interactions are stronger in the copper complex 4. Fits of magnetic data for compounds 1, 3 and 4 with appropriate models led to J values of −0.6, −1.5 and −99.0 cm−1 respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Cobalt(II), Nickel(II), Copper(II), and Zinc(II) Complexes with a p‐tert‐Butylcalix[4]arene Fitted with Phosphinoyl Pendant Arms

AbstractA series of complexes of MIIX2 transition metal salts (X = ClO4, M = Co, Ni, Cu, Zn; X = Cl, M = Cu, Zn) with a calix[4]arene substituted at the lower rim {L = 5,11,17,23‐tetra‐tert‐butyl‐25,26,27,28‐tetrakis[(dimethylphosphinoyl)methoxy]calix[4]arene} are isolated and characterized. Two different stoichiometries are evidenced, 1:1 for the CoII, NiII, and CuII complexes, independently of the anion (Cl− or ClO4−), as well as for the Zn(ClO4)2 complex, while a 2:1 metal/ligand ratio is found for the complex with ZnCl2. The coordination mode and structure of the complexes are investigated by several spectroscopic and magnetochemical methods, both in the solid state and in solution. Coordination through the phosphoryl groups of the ligand is ascertained by X‐ray diffraction and IR and NMR spectroscopic data. The crystal structure of the 2:1 Zn compound (triclinic, P$\bar 1$ , Z = 2) shows the presence of the tetrametallic species Zn4L2 with three different tetrahedral Zn environments, ZnCl2O2, ZnCl3O, and ZnClO3, the latter bridging two ligand molecules. Magnetic susceptibility, EPR data, and electronic spectra are indicative of a tetrahedral arrangement of the ligands in the CoII (high‐spin d7) 1:1 complex, which is also most probably the ligand geometry in the NiII and CuII 1:1 complexes. In solution, the extent of the interaction between L and the MII ions has been determined by UV/Vis spectrophotometric titrations. The resulting stability constants for 1:1 complexes are in the range log K1 = 4.8−5.4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

P-tert-Butylthiacalix[6]arene as a Clustering Ligand. Syntheses and Structures of CoII5, NiII4, and Mixed-Metal MIINiII4 (M = Mn, Co, and Cu) Cluster Complexes, and a Novel Metal-Induced Cluster Core Rearrangement

Abstract Using p-tert-butylthiacalix[6]arene (H6L) as a clustering ligand, five cluster complexes having CoII5 (2), NiII4 (3) and MIINiII4 (M = CoII (4), MnII (5), and CuII (6)) cores were synthesized. In all the complexes except for 3, a pinched conic L6− acts as a pentanucleating ligand that involves a similar pyramidally arranged cluster core. Each mixed metal complex 4–6 involves four tetragonally arranged NiII ions occupying the basal plane of the pyramid and a MII ion placed at the apex position. In 3, H2L4− is in a cone conformation and the four NiII ions are arranged on the donor surface of H2L4− in a zigzag manner. The mixed metal complexes 4–6 are synthesized by reacting 3 and the appropriate M(AcO)2 in a 1:1 ratio with a novel metal-induced core rearrangement occurring. In this reaction, the insertion of a MII ion at the apex position forces the calixarene to take a cone conformation and the NiII4 array rearranges to form a tetragonal cluster.

Crystal Structures and Intercalation Reactions of Three‐Dimensional Coordination Polymers [M(H2O)2]2 [Mo(CN)8]×4H2O (M: Co, Mn).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crystal Structures and Intercalation Reactions of Three‐Dimensional Coordination Polymers [M(H2O)2]2[Mo(CN)8]·4H2O (M = Co, Mn)

AbstractTwo coordination polymers [MII(H2O)2]2[MoIV(CN)8]·4H2O [MII = Co (1), Mn (2)] were prepared as monocrystals and structurally characterised. These compounds crystallise in the tetragonal systems I4/m (1) and I4/mcm (2) and form three‐dimensional networks containing channels occupied by two types of water molecules, i.e. coordinated to MII and crystallised ones. The dehydration of these materials occurs topochemically to give [MII(H2O)]2[MoIV(CN)8] compounds having an open metal coordination site on the MII ions that may be accessible to coordination by other species and serve as a reaction site. The intercalation of water, ammonia and amines has been studied. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Ground Spin State Variation in Carboxylate‐Bridged Tetranuclear [Fe2Mn2O2]8+ Cores and a Comparison with Their [Fe4O2]8+ and [Mn4O2]8+ Congeners

AbstractSyntheses of ten new tetranuclear complexes containing the [MA(μ3‐O)2MB]8+ butterfly core [MA = MB = FeIII (1 and 2), MA = MB = MnIII (3 and 4) and MA = FeIII, MB = MnIII (5−10)] using 1,4,7‐trimethyl‐1,4,7‐triazacyclononane (L) as the capping ligand, salicylaldoximato dianion (salox2−) and six different carboxylate anions as bridging ligands, are described. The crystal structures of [L2Fe2(μ3‐O)2(salox)2(diphenylglycolate)3Fe2](ClO4) (1), [L2Mn2(μ3‐O)2(salox)2(diphenylglycolate)3Mn2](ClO4) (3), [L2Fe2(μ3‐O)2(salox)2(acetate)3Mn2](ClO4) (5), [L2Fe2(μ3‐O)2(salox)2(diphenylglycolate)3Mn2](ClO4) (6), and [L2Fe2(μ3‐O)2(salox)2(benzoate)3Mn2](ClO4) (8) were determined by X‐ray crystallography. The complexes are isostructural, with MIII ions disposed in a butterfly core where bridging between the MIII ions occurs via two μ3‐oxo anions. In complexes 5, 6 and 8 the “wing‐tip” positions of the butterfly are occupied by the LFe3+ units, whereas the “body” metal ions are d4 high‐spin MnIII ions. Complexes 1−10 have been characterised by variable‐temperature (2−290 K) magnetic susceptibility measurements (1 T) and by Mössbauer spectroscopy. A “2J” model has been applied to simulate the experimental μeff vs. T plots. Overall exchange interactions are antiferromagnetic in nature. Complexes with the Fe4O2 core (1 and 2) and the Mn4O2 core (3 and 4) possess an St = 0 and St = 3 ground state, respectively, regardless of the nature of the bridging carboxylate ligand. In contrast, changing the bridging carboxylates in the [Fe2Mn2O2] core from acetate (5) to diphenylglycolate (6), triphenyl acetate (7), benzoate (8), chloroacetate (9) and propionate (10), results in a variation of the ground state from St = 1 to St = 3, due to spin frustration of the “body” manganese centres. The spin‐correlation diagram for the Fe2Mn2O2 butterfly arrangement clearly demonstrates the ground state variation as a function of the ratio of two competing coupling interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The design of fluorescent sensors for anions: taking profit from the metal–ligand interaction and exploiting two distinct paradigms

Fluorescent sensors are molecular systems consisting of a receptor moiety and of a fluorogenic fragment, which are capable of recognising a given analyte and signalling recognition through a variation of the emission intensity. The fluorogenic fragment responsible of the signal can be associated to the receptor either covalently or non-covalently, giving rise to two well distinct classes of fluorosensors and sensing paradigms. The design of fluorescent sensors is described, with a special attention to the sensing of anionic groups (including those of amino acids). In any case, it seems convenient that the receptor moiety contains one or more metal centres, which establish strong coordinative interactions with the envisaged anionic substrate. Selectivity is related to the energy of the metal–analyte interaction and can be achieved by taking profit of the concepts developed in more than one hundred years of coordination chemistry. As an example, recognition and sensing of the amino acid histidine is considered in detail, which is based on the attitude of the imidazole residue to deprotonate and bridge two MII ions prepositioned at the right distance, within a defined coordinative framework (M = Cu, Zn).

Relativistic effects in iron-, ruthenium-, and osmium porphyrins

Abstract Nonrelativistic and relativistic DFT calculations are performed on four-coordinate metal porphyrins MP and their six-coordinate adducts MP(py)2 and MP(py)(CO) (py=pyridine) with M=Fe, Ru, and Os. The electronic structures of the MPs are investigated by considering all possible low-lying states with different configurations of nd-electrons. FeP and OsP have a 3 A 2 g ground state, while this state is nearly degenerate with 3 E g for RuP. Without relativistic corrections, the ground states of both RuP and OsP would be 3 E g . For the six-coordinate adducts with py and CO, the strong-field axial ligands raise the energy of the M dz2-orbital, thereby making the MII ion diamagnetic. The calculated redox properties of MP(py)2 and MP(py)(CO) are in agreement with experiment. The difference between RuP(py)(CO) and OsP(py)(CO), in terms of site of oxidation, is due to relativistic effects.

Molecule-based magnets formed by bimetallic three-dimensional oxalate networks and chiral tris(bipyridyl) complex cations. The series [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion).

The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where the chiral [Z(bpy)3]2+ and ClO4- counterions are located. These compounds behave as soft ferromagnets with ordering temperatures up to 6.6 K and coercive fields up to 8 mT.

Multiple expression of molecular information: enforced generation of different supramolecular inorganic architectures by processing of the same ligand information through specific coordination algorithms

The multisubunit ligand 2 combines two complexation substructures known to undergo, with specific metal ions, distinct self-assembly processes to form a double-helical and a grid-type structure, respectively. The binding information contained in this molecular strand may be expected to generate, in a strictly predetermined and univocal fashion, two different, well-defined output inorganic architectures depending on the set of metal ions, that is, on the coordination algorithm used. Indeed, as predicted, the self-assembly of 2 with eight CuII and four CuI yields the intertwined structure D1. It results from a crossover of the two assembly subprograms and has been fully characterized by crystal structure determination. On the other hand, when the instructions of strand 2 are read out with a set of eight CuI and four MII (M = Fe, Co, Ni, Cu) ions, the architectures C1-C4, resulting from a linear combination of the two subprograms, are obtained, as indicated by the available physico-chemical and spectral data. Redox interconversion of D1 and C4 has been achieved. These results indicate that the same molecular information may yield different output structures depending on how it is processed, that is, depending on the interactional (coordination) algorithm used to read it. They have wide implications for the design and implementation of programmed chemical systems, pointing towards multiprocessing capacity, in a one code/ several outputs scheme, of potential significance for molecular computation processes and possibly even with respect to information processing in biology.

Use of Raman micro-spectroscopy in the characterization of MIIFe2O4 (M = Fe, Zn) electric double layer ferrofluids

MIIFe2O4 (M = Fe, Zn) electric double layer ferrofluids (edl-ferrofluids) were investigated and characterized by Raman micro-spectroscopy as solids (powder) or in solution forming magnetic fluids. The Raman spectra showed that the nanoparticles forming the magnetic fluids have different compositions depending on the MII ion used in their preparation. In the case of FeFe2O4 edl-ferrofluid, maghemite, magnetite, an amorphous non-stoichiometric oxyhydroxide [FeOx(OH)3 − 2x, x<1] and Fe(OH)3 phases are present. In the case of the ZnFe2O4 edl-ferrofluid, a magnetite-like structure where the FeII centers were replaced by the ZnII ions is present. A model of the distribution of the different chemical phases on the nanoparticles is presented. The Raman spectrum of the FeFe2O4 edl-ferrofluid excited close to an absorption band of the sample at 650 nm presents several Raman features above 900 cm−1 that are not observed for the ZnFe2O4 edl-ferrofluid sample. These results have been interpreted considering the resonant excitation of the density of phonon states with k ≠ 0 due to quantum size effects. Copyright © 2000 John Wiley & Sons, Ltd.

Polarized neutron diffraction study of the extended honeycomb molecular network d20−P(C6D5)4MnFe(C2O4)3

The MII and MIII magnetic ions in the extended molecular network P(C6D5)4MnFe(C2O4)3 form a two-dimensional honeycomb magnetic lattice. The Mn2+ and Fe3+ ions alternate in the extended network which is formed by the oxalate (C2O4) ligands. These hexagonal layers are separated and charge compensated by large [P(C6D5)4]+ ions, positioned in between the honeycomb layers. P(C6D5)4MnFe(C2O4)3 orders magnetically at TN=27(1) K. A full neutron spin polarization study of the neutron scattering cross section has been carried out which allows the unambigious separation of the magnetic cross section from the total diffraction process. The magnetic structure can be described with the magnetic Shubnikov group R3c. The magnetic moments are antiferromagnetically aligned along the c axis while the Mn2+ and Fe3+ ions form an antiferromagnetic alignment on the honeycomb lattice.

Synthesis and Structural Study by Wide-Angle X-ray Scattering (WAXS) of Polymeric {Ln2[M(opba)]3}·S Compounds Containing 4f LnIII and 3d MII {Ln2[M(opba)]3}·S Ions [opba =ortho-Phenylenebis(oxamato), S = Solvent Molecules

The compounds of formula Ln2[M(opba)]3·xH2O·yDMSO containing 4f LnIII and 3d MII ions have been synthesized; opba stands for ortho-phenylenebis(oxamato). These compounds crystallize poorly, and hence structural information has been obtained from the wide angle X-ray scattering (WAXS) technique. It has been shown that the compounds present the same ladder-like motif as that previously described for Tm2[Cu(opba)]3·4H2O·10DMF. Changing the LnIII and/or MII ions results in more or less pronounced distortions of the ladders. For a given MII ion, changing the LnIII ion from LaIII to LuIII results in a decrease of the Ln–M distance parallel to the lanthanide contraction. In the same way, for a given rare earth, changing the MII ion from CuII to NiII and ZnII ions also results in the decrease of the Ln–M distance in accord with the decreasing radii of the MII ions. The structural details have been analyzed and discussed.

Crystallographic Study on Metal(II) Complexes with N-(2-Nitrophenylsulfonyl)glycine

The interaction of MII ions (MII =Mn II, CoII, NiII, CuII, ZnII, CdII, PbII) with N-(2-nitrophenylsulfonyl)- glycine (NO2psglyH2) leads to the formation at acidic pH of the complex carboxylate-type M(NO2psgly- O)2.x H2O species. At higher pH the deprotonation reaction of the sulfonamide nitrogen takes place, leading to the formation of the M(NO2psgly-N,O).x H2O species where the ligand acts as a chelating agent toward the metal ion through the carboxylic oxygen and the deprotonated sulfonamide nitrogen. In ternary systems the addition of 2,2′-bipyridine (bpy) allows the deprotonation of the sulfonamide nitrogen also in presence of metal ions such as ZnII, CoII and NiII, which were inactive in the binary system, and the solid compounds isolated are in the M/bpy/L molar ratio 1 : 1 : 1 (MII = CuII , ZnII ) or 1 : 2 : 1(MII = CoII , NiII, CdII). Here we describe the crystal and molecular structures of NO2psglyH2 (1), [Pb(NO2psgly-N,O)]n (2), [Cd(bpy)2(NO2psgly-N,O)].H2O (3) and [Cu(bpy)(NO2psgly-N,O)(H2O)] (4).

A new family of 2D antiferromagnets: the layered phosphonates MII (RPO3) · H2O; M  Mn, Fe, Co, Ni; R = alkyl, phenyl

Magnetic susceptibility data are reported for the divalent metal phosphonates II(RPO3) · H2O (M  Mn, Fe, Co, Ni; R = alkyl, phenyl). The quasi 2D square lattice formed by the MII ions within these compounds leads to 2D antiferromagnetic properties.

New ligands for complexation of lanthanoids: the synthesis and structures of a nonadentate Schiff-base ligand (L1) and of the complexes [ML1(OH2)](ClO4)3·3MeNO2(M = La, Pr) and [YL1](ClO4)3·3MeCN

The synthesis and structures of a nonadentate Schiff-base ligand L1, prepared from tris(2-aminoethyl)amine and 2,6-diformyl-4-methylphenol, and of its complexes with MIII ions (M = La, Pr and Y) are reported; [ML1(OH2)](ClO4)3·3MeNO2(M = La, Pr) are ten-coordinate species while [YL1](ClO4)3·3MeCN is nine-coordinate.

Calculation of spin and charge densities in hexaaqua transition-metal(II) ions and their comparison with experiment

All-electron calculations using the DV-Xα implementation of the local-density-approximation formalism are presented for the hexaaqua MII ions of the first transition series from VII to ZnII. The experimental Ci symmetry geometries and limited basis sets are employed. The results are compared with the X-ray and polarised neutron diffraction experiments, which yield real-space charge and spin distributions respectively, by means of maps and orbital population analyses. Although the calculations on the one hand and the experiments on the other have limitations in the confidence with which interpretations can be made for individual members, the comparison of trends across the series of metals proves valuable. Both calculations and experiments reflect the importance of the effects of the Jahn–Teller distortions for the CrII and CuII cases and illustrate the effects of covalence. The calculations support interpretations of the experimental data which emphasise the role of spin polarisation; it is a major feature of the electron distributions in the ions of the first transition series. It is indeed responsible for the repeated observation that the transfer of spin population by covalence in the metal–ligand bonding is much less than that of charge. This confirms the long-obvious statement that single configuration Hartree–Fock theory is an unsatisfactory basis for the description of bonding in transition-metal complexes. The experimental observation that the low symmetry environment of the hexaaqua MII ions in the salts studied has little effect on the details of the electron distribution, apart, of course from the Jahn–Teller affected cases of CrII and CuII, and the π-orbitally degenerate FeII and CoII ions, is supported by the calculations. The fact that similar calculations have been made for the entire series of metal(II) ions experimentally available is of more importance than is the loss of accuracy which follows from the limited basis sets used for the individual cases.

Metal ion catalysis in the hydroxyalkylation of phenol with glyoxylic acid

AbstractThe hydroxyalkylation reaction of phenol with glyoxylic acid in aqueous medium is found to be homogeneously catalyzed by various metal ions. Catalysis with MII ions results in a reaction product with an ortho/para ratio of 0.2 to 1.1, whereas catalysis using higher valent cations, because of their ability to form mixed complexes with phenol and glyoxylic acid, affords a reaction product with an ortho/para ratio of 1.3 to 28. The catalyzed Cannizzaro reaction of glyoxylic acid was observed as a side‐reaction. Addition of a suitable inert ligand, e.g. oxalic acid or NTA, is shown to decrease the ortho/para ratio and to suppress the Cannizzaro reaction.The coordination of glyoxylic acid and its hydrate with several cations has been studied by NMR techniques and a mechanism of the catalyzed hydroxyalkylation and Cannizzaro reaction is proposed.

Mössbauer-spektroskopische Untersuchungen an Na2MnFeF7 / Mössbauer Spectroscopic Investigation of Na2MnFeF7

In contrast to the Mössbauer spectrum of the orthorhombic compound Na2NiFeF7 that of the manganous compound Na2MnFeF7 gives evidence of two different iron positions. This rules out Na2MnFeF7 to be isostructural with Na2NiFeF7, which crystallizes like most compounds Na2MIIMIIIF7 in the weberite structure, the MIII ions occupying only one site in space group Imm 2-C2v 20. The Mössbauer data evaluated for the two iron sites (Fe 1/Fe 2 respectively) in Na2MnFeF7 are: θ = 0/90°, φ = undetermined/70°, η = 0.6 both, Η = 551/541 kOe, Vzz = ± 2.7 · 1018 Vcm-2 both. NaMnFeF7 is antiferromagnetic with a Neél temperature of TN = 94 Κ for both iron positions.