Intermetallic Separation Research Articles

Synergic Catalysis: the Importance of Intermetallic Separation in Co(III)K(I) Catalysts for Ring Opening Copolymerizations.

Dinuclear polymerization catalysts can show high activity and control. Understanding how to design for synergy between the metals is important to improving catalytic performances. Three heterodinuclear Co(III)K(I) catalysts, featuring very similar coordination chemistries, are prepared with different intermetallic separations. The catalysts are compared for the ring-opening copolymerization (ROCOP) of propene oxide (PO) with CO2 or with phthalic anhydride (PA). The catalyst with a fixed, wide intermetallic separation, LwideCoK(OAc)2 (Co-K = 8.06 Å), shows very high activity for PO/PA ROCOP, but is inactive for PO/CO2 ROCOP. On the other hand, the catalyst with a fixed, narrow intermetallic separation, LshortCoK(OAc)2 (Co-K, 3.59 Å), shows high activity for PO/CO2 ROCOP, but is much less active for PO/PA ROCOP. A bicomponent catalyst system, comprising a monometallic complex LmonoCoOAc used with an equivalent of KOAc[18-crown-6], shows high activity for both PO/CO2 and PO/PA ROCOP, provided the catalyst concentration is sufficiently high, but underperforms at low catalyst loadings. It is proposed that the two lead catalysts, LwideCoK(OAc)2 and LshortCoK(OAc)2, operate by different mechanisms for PO/PA and PO/CO2 ROCOP. The new wide separation catalyst, LwideCoK(OAc)2, shows some of the best performances yet reported for PO/PA ROCOP, and suggests other catalysts featuring larger intermetallic separations should be targeted for epoxide/anhydride copolymerizations.

Cooperativity in Shape-Persistent Bis-(Zn-salphen) Catalysts for Efficient Cyclic Carbonate Synthesis under Mild Conditions.

A series of conformationally rigid (Zn-salphen)2 complexes with a planar bridging component (xanthene or dibenzofuran) are described. Conformational changes for these assemblies are essentially limited to the axial rotation of the Zn-salphen moieties; however, such geometric constraints crucially permit the subtle tuning of the intermetallic separation and geometry to potentially enhance catalytic activity (and cooperative effects). The complexes have been investigated as catalysts in conjunction with nBu4NI for the coupling of CO2 with epoxides. Selected dibenzofuran derivatives are significantly more active for the production of cyclic carbonate than their mononuclear analogues under identical conditions and concentrations of Zn sites. High initial turnover frequencies (up to 29 000 h-1; 14 500 h-1 per Zn, using 10 bar of CO2 at 95 °C) and excellent efficiencies under mild conditions (1 bar of CO2 at 55 °C) have been achieved. Kinetic studies using in situ (ReactIR) spectroscopy and density functional theory calculations have been performed, which reveal the existence of an intramolecular rate component and a preference for the cooperative pathway as well as transition states that depict the Zn sites operating in tandem. Taken together, these results provide strong evidence of cooperative reactivity in these Zn2 catalysts.

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands.

The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR2 etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

Formation of a composite structure in Ti-Cr alloys using reversible hydrogen alloying

The aim of this work is to study the regularities of the influence of hydrogen doping on the course of phase and structural transformations in Ti-Cr alloys. The influence of the amount of hydrogen on the preferred sites of intermetallic separation was studied. The influence of hydrogen on the lines of variable solubility of the state diagram Ti-Cr is studied. The possibility of controlling the process of structure formation in titanium alloys with p-eutectoid-forming stabilizers by additional alloying with hydrogen and obtaining such types of structures that are not typical for them with traditional methods of technological influence is shown.

Understanding crystal structure and morphology evolution of Fe, Mn, Cr-containing phases in Al-Si cast alloy

As a common detrimental element in Al-Si cast alloy, Fe can be effectively removed by Fe-containing intermetallic separation in the alloy melt. However, the thermodynamic formation mechanism and growth morphology evolution of high separable Fe-containing intermetallic have not been investigated and clarified in detail until now. In this study, thermodynamic calculation, three-dimensional (3D) growth morphology and crystal structure were characterized to investigate the effect of Mn and Cr on morphology evolution, crystal structure and precipitation temperature of Fe-containing intermetallics. It is demonstrated that the addition of Mn and Cr can increase the precipitation temperatures of Fe-containing intermetallics in melt, and also result in the variation of crystal structures from monoclinic γ-AlFeSi to cubic α-AlFeMnCrSi phases. Moreover, the addition of Mn and Cr significantly changes the morphology of Fe-containing intermetallics from plate-like to cubic shapes. α-AlFeMnCrSi phase precipitated at high temperature exhibits the same structural basis as α-Al9Mn2Si2. The Fe-containing phase of cubic structure provides higher thermo stability which is in favor of its sufficient precipitation and separation.

One-Pot Self-Assembly of Dinuclear, Tetranuclear, and H-Bonding-Directed Polynuclear Cobalt(II), Cobalt(III), and Mixed-Valence Co(II)/Co(III) Complexes of Schiff Base Ligands with Incomplete Double Cubane Core.

The reaction of 2,6-diformyl-4-methylphenol (DFMF) with 1-amino-2-propanol (AP) and tris(hydroxymethyl)aminomethane (THMAM) was investigated in the presence of Cobalt(II) salts, (X = ClO4−, CH3CO2−, Cl−, NO3−), sodium azide (NaN3), and triethylamine (TEA). In one pot, the variation in Cobalt(II) salt results in the self-assembly of dinuclear, tetranuclear, and H-bonding-directed polynuclear coordination complexes of Cobalt(III), Cobalt(II), and mixed-valence CoIICoIII: [Co2III(H2L−1)2(AP−1)(N3)](ClO4)2 (1), [Co4(H2L−1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]·4CH3OH (2), [Co2IICo2III(HL−2)2(µ-CH3CO2)2(µ3-OH)2](NO3)2·2CH3CH2OH (3), and [Co2IICo2III (H2L12−)2(THMAM−1)2](NO3)4 (4). In 1, two cobalt(III) ions are connected via three single atom bridges; two from deprotonated ethanolic oxygen atoms in the side arms of the ligands and one from the1-amino-2-propanol moiety forming a dinuclear unit with a very short (2.5430(11) Å) Co-Co intermetallic separation with a coordination number of 7, a rare feature for cobalt(III). In 2, two cobalt(II) ions in a dinuclear unit are bridged through phenoxide O and μ3-1,1,1-N3 azido bridges, and the two dinuclear units are interconnected by two μ-1,1-N3 and two μ3-1,1,1-N3 azido bridges generating tetranuclear cationic [Co4(H2L−1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]2+ units with an incomplete double cubane core, which grow into polynuclear 1D-single chains along the a-axis through H-bonding. In 3, HL2− holds mixed-valent Co(II)/Co(III) ions in a dinuclear unit bridged via phenoxide O, μ-1,3-CH3CO2−, and μ3-OH− bridges, and the dinuclear units are interconnected through two deprotonated ethanolic O in the side arms of the ligands and two μ3-OH− bridges generating cationic tetranuclear [Co2IICo2III(HL−2)2(µ-CH3CO2)2(µ3-OH)2]2+ units with an incomplete double cubane core. In 4, H2L1−2 holds mixed-valent Co(II)/Co(III) ions in dinuclear units which dimerize through two ethanolic O (μ-RO−) in the side arms of the ligands and two ethanolic O (μ3-RO−) of THMAM bridges producing centrosymmetric cationic tetranuclear [Co2IICo2III (H2L1−2)2(THMAM−1)2]4+ units which grow into 2D-sheets along the bc-axis through a network of H-bonding. Bulk magnetization measurements on 2 demonstrate that the magnetic interactions are completely dominated by an overall ferromagnetic coupling occurring between Co(II) ions.

A Cyclometalated N‐Heterocyclic Carbene: The Wings of the First Pt2(II,II) Butterfly Oxidized by CHI3

The X-ray study on a single crystal of the butterfly-like complex [{Pt(C^C*)(μ-pz)}2 ] (1), containing a cyclometalated N-heterocyclic carbene ligand as wings (HC^C*=1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), showed three molecules in the asymmetric unit with intermetallic separations (Å) of 3.2294(4) (1A), 3.2834(4) (1B), and 3.1208(6) (1C). From the reaction of 1 with excess of CHI3 in the air and the sunlight, complex [{Pt(C^C*)(μ-pz)I)}2 ] (2) (dPt-Pt =2.6079(2) Å) was obtained as the major product, while [IPt(C^C*)(μ-pz)2 Pt(C^C*)CHI2 ] (3) (dPt-Pt =2.6324(3) Å) was obtained as the major product under argon atmosphere in the dark. Experimental and theoretical investigations showed that an easily accessible radical-like mechanism operates under thermal conditions, with dioxygen acting as an efficient radical (R. ) scavenger. The oxidation of a Pt2 (II,II) "butterfly" by CHI3 to give metal-metal bonded Pt2 (III,III) compounds is described now for the first time.

Shortwave infrared luminescent Pt-nanowires: a mechanistic study of emission in solution and in the solid state.

Several complexes of "PtL2" composition containing two cyanoxime anions - 2-oximino-2-cyano-N-piperidineacetamide (PiPCO-) and 2-oximino-2-cyano-N-morpholylacetamide (MCO-) - have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL2]n 1D polymers, while for the MCO- anion a red, solvent containing dimeric [Pt(MCO)2·DMSO]2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL2 units are arranged into anisotropic extended solid [PtL2]n polymers with the help of PtPt metallophilic interactions. Crystal structures of monomeric PtL2 (L = PiPCO-, MCO-) and red dimeric [Pt(MCO)2·DMSO]2 complexes were determined and revealed the cis-arrangement of cyanoxime anions. The Pt-Pt distance in the "head-to-tail" red dimer was found to be 3.133 Å. The structure of the polymeric [Pt(PiPCO)2]n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 Å intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt(iii) species. Both pure dark-green [PtL2]n polymers showed a considerable room temperature electrical conductivity of 20-30 S cm-1, which evidences the formation of a mixed valence Pt(ii)/Pt(iv) system. We discovered that these 1D polymeric [PtL2]n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL2]n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence "metal wires" held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL2]n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL2]n in the -190-+60 °C range was studied as well.

Synthesis, crystal structure and luminescence properties of “paddle wheel” and “butterfly” shaped polynuclear complexes

A series of metal cluster-based complexes were constructed from the reaction of metal ions (FeIII, CuII, ZnII) and ligand (2-({2-[2-carbosybenzoy])oxy]-ethoxy}carbonyal)benzoic acid) (H2L) in CH3CH2OH, CH3OH, (C2H5)3N and C2H3N. Two paddle wheel trinuclear clusters [Fe3(μ3-O)(μ2-η2-L)3(CH3OH)3]NO3·C2H5OH·CH3OH (1) and [Fe3(μ3-O)(μ2-η2-L)3(H2O)3]NO3·5CH3OH·H2O (2), one tetranuclear cluster [Cu2(μ2-L)2(C2H3N)2·2C2H3N]2 (3) and one butterfly shaped dinuclear cluster [Zn2(μ2-L)2(C2H5OH)2]·2CH3OH (4) were obtained. Complexes 1, 2, and 4 are further assembled by intermolecular hydrogen bonds to form supramolecular frameworks. In complex 3, the flexible benzoic acid ligand chelates with two CuII, which induces a decrease of CuCu intermetallic separation (rang from 2.644 to 2.657 Å). The structures of the complexes are characterized by elemental analyses, Infrared spectroscopy (IR spectroscopy), thermal gravimetry (TG) analyses, single crystal X-ray diffraction and powder X-ray diffraction techniques (PXRD), and high resolution mass spectra (HRMS). The luminescent properties of the clusters 1–4 are also studied, the results show that the cluster 4 exhibits blue fluorescence at room temperature.

Dinuclear nickel complexes of divergent Ni⋯Ni separation showing ancillary ligand addition and bio-macromolecular interaction

Reactions of ligand HL with nickel(ii) salts produce a family of five [Ni2] complexes of varying co-ligand environments and intermetallic separations and show prominent interactions with HSA and CT-DNA.

Dinuclear μ-fluoro cations of copper, silver and gold

Terminal fluoride complexes of the monovalent group 11 metals, supported by N-heterocyclic carbene (NHC) ligands, react with one-half equivalent of triphenylmethyl cation to form fluoride-bridged dinuclear cations. An improved preparation of the starting terminal fluorides is introduced. The crystal structures of the cations display bent MFM arrangements with large intermetallic separations. The bridging fluorides are highly labile, undergoing facile hydrolysis. The fluoride-bridged digold complex adds across an allene CC bond to form a diaurated allylic fluoride.

Synthesis, crystal structures, spectroscopic and electrochemical studies on Cu(II) and Ni(II) complexes with compartmental nitrogen–oxygen mixed donor ligands

The synthesis and characterization of two new N2O4 donor type ligands, 2-{[(2-{3-[2-({[(2-hydroxyphenyl)methylidene]amino}methyl)phenoxy]propoxy}benzyl)imino]methyl}phenol (H2L1) and 2-[({2-[3-(2-{[(2-hydroxybenzyl)amino]methyl}phenoxy)propoxy]benzyl}amino)methyl]phenol (H2L2), and their metal complexes with Cu(II) and Ni(II) metal ions are reported. The ligands and complexes have been characterized by 1H NMR, FT-IR, UV–Vis absorption spectroscopy, single-crystal X-ray diffraction, CHN elemental analysis and cyclic voltammetry (CV). The redox behavior of the two complexes has been studied by CV. Copper and nickel complexes of Schiff base (H2L1) and reduced Schiff base (H2L2) showed different behaviors because the structure of the complexes depends of the ligand. The complex [Cu2L12]·2CH3OH (1) is dinuclear with the two metal centers bridged exclusively by the ligands, consisting of two distorted square planar CuN2O2 chromophors with large intermetallic separation (8.879Å). Complex [Ni4L22(CH3COO)4]·4CH3OH (2) consists of tetranuclear Ni4 unit of two symmetry related hexacoordinated nickel atoms having distorted octahedral NiN2O4 and NiO6 environments, and contains two types of acetate coordination modes, namely, bridging bidentate (μ2-η1, η1), and asymmetric chelating bridging (μ2-η2, η1).

Synthesis, structure and luminescence of new dinuclear cyanido-bridged AgI–AuI one-dimensional coordination polymer

Abstract A new alternating chain compound consisting of gold(I) and silver(I) bridged by cyanides is reported. The Ag(I) ion is functionalized by 2 triphenyl phosphane ligands, resulting in the formula [Au(C N)2(PPh3)2Ag]n. The compound has been prepared by room temperature reaction of triphenyl phosphane with the cyanide salts of silver(I) and gold(I). The product has been characterized and its single crystal X-ray structure was determined. In the molecular structure of the complex, the Au(I) centers exhibit the expected linear, two-coordinate geometry with C-bound cyanides, whereas the Ag(I) centers adopt a tetrahedral geometry in a AgN2P2 chromophore. The shortest hetero intermetallic separation distance is 4.94(7) A. No aurophilic interactions are observed, but only the non-conventional C H…Au hydrogen interactions are present. Upon excitation at 325 nm, a quite intense luminescence at 475 nm, assigned on the basis of DFT calculations to MMLCT, is observed, which amounts to ca. 10% of the luminescence intensity of the best known luminescent compounds.

Synthesis Characterization, X‐ray Structures, and Solution Studies of Dinuclear Zinc(II) Complexes of Acyclic Schiff Base Ligands

AbstractDizinc(II) complexes of two acyclic Schiff‐base ligands L1– and L2– were synthesized by Schiff base condensation of 2‐[3‐(2‐formylphenoxy)‐2‐hydroxypropoxy]benzaldehyde (PL) with 1,2‐diaminopropane and 1,2‐diaminoethane, respectively, in the presence of zinc(II) salts. The isolation of a selection of 2:1 (metal:ligand) complexes of zinc(II) was carried out and conductance measurements, IR, UV/Vis absorption, and fluorescence emission spectroscopy, as well as X‐ray diffraction were employed to probe the nature of the respective complexes in both solid and solution states. The molecular structure of [Zn2L1(NO3)3] (1) complex consists of two six‐coordinate atoms, which are bridged by the deprotonated hydroxy group and one 1,3‐bridging nitrate anion. The structure of [Zn2L2(NO3)(H2O)2](NO3)2·CH3OH (3) consists of a dizinc cation and two nitrate anions as counterions. In compound 3, each zinc atom is bound to water instead of a terminal nitrate anion in a distorted octahedral arrangement. The intermetallic separation distance of Zn···Zn in 3 (3.376 Å) is slightly smaller than 1 (3.403 Å) and is similar to that found in zinc phosphotriesterase (3.5 Å). The π–π interactions between the benzene rings of adjacent molecules in 3 are stronger than in 1.

Intermetallic Interactions Within Solvated Polynuclear Complexes: A Misunderstood Concept

The entry of the gladiators: Two effects oppose each other for control of the intermetallic interactions within polynuclear (supra)molecular helicates in solution (see picture). Coulombic interactions produce large intermetallic repulsion at short distance, and solvation effects result in a large intermetallic attraction for small pseudo-spherical ions with short intermetallic separations d.

Understanding, Controlling and Programming Cooperativity in Self-Assembled Polynuclear Complexes in Solution

Deviations from statistical binding, that is cooperativity, in self-assembled polynuclear complexes partly result from intermetallic interactions DeltaE(M,M), whose magnitudes in solution depend on a balance between electrostatic repulsion and solvation energies. These two factors have been reconciled in a simple point-charge model, which suggests severe and counter-intuitive deviations from predictions based solely on the Coulomb law when considering the variation of DeltaE(M,M) with metallic charge and intermetallic separation in linear polynuclear helicates. To demonstrate this intriguing behaviour, the ten microscopic interactions that define the thermodynamic formation constants of some twenty-nine homometallic and heterometallic polynuclear triple-stranded helicates obtained from the coordination of the segmental ligands L1-L11 with Zn(2+) (a spherical d-block cation) and Lu(3+) (a spherical 4f-block cation), have been extracted by using the site binding model. As predicted, but in contrast with the simplistic coulombic approach, the apparent intramolecular intermetallic interactions in solution are found to be i) more repulsive at long distance (DeltaE(1-4)(Lu,Lu)>DeltaE(1-2)(Lu,Lu)), ii) of larger magnitude when Zn2+ replaces Lu3+ (DeltaE(1-2)(Zn,Lu)>DeltaE(1-2)(Lu,Lu) and iii) attractive between two triply charged cations held at some specific distance (DeltaE(1-3)(Lu,Lu)<0). The consequences of these trends are discussed for the design of polynuclear complexes in solution.

Aqua bridged Cu 2 dimer of a heptadentate N 4O 3 coordinating ligand: Synthesis, structure and magnetic properties

The N 4O 3 coordinating heptadentate imidazolidinyl phenolate ligand, H 3L (2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) forms with Cu(II) a rare aqua bridged complex [{Cu 2(μ-L)(μ-H 2O)} 2](ClO 4) 2 · 4.5H 2O ( 1 · 4.5H 2O). Complex 1 · 4.5H 2O contains two crystallographically different but chemically equivalent dinuclear [Cu 2(μ-L)(μ-H 2O)] + cationic units in the asymmetric unit. The copper atoms of each dinuclear unit are in a distorted square-pyramidal environment and are held together by phenolate, imidazolidinyl and aqua bridges with a Cu···Cu separation of av. 3.34 Å. The compound exhibits a very weak antiferromagnetic exchange interaction ( J = −0.77 cm −1, Ĥ = −2 J Ŝ 1 Ŝ 2) between the two copper(II) ( S = 1/2) ions. The 1H NMR spectrum of the complex shows a total of 17 hyperfine shifted peaks, as expected from the idealized C s symmetry of the compound, spread over a very large window of chemical shift, spanning about 250 ppm. The complex, having an appropriate intermetallic separation for catechol binding, shows catecholase like activity in MeCN at 25 °C, with the aerobic oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) to 3,5-di- tert-butylquinone (3,5-DTBQ).

Two manganese(II) complexes based on anthracene-9-carboxylate: Syntheses, crystal structures, and magnetic properties

To explore the influence of the anthracene ring skeleton, with a large conjugated π-system, on the structures and properties of its complexes, two MnII complexes with anthracene-9-carboxylate ligand were synthesized and structurally characterized: {[Mn(L)2(H2O)2](H2O)}∞ (1) and [Mn2(L)4(phen)2(μ-H2O)](CH3OH) (2) (L = anthracene-9-carboxylate and phen = 1,10-phenanthroline). Complex (1) has a one-dimensional (1D) chain structure that is further assembled to form a two-dimensional (2D) sheet, and then an overall three-dimensional (3D) network by π···π stacking and/or C–H···π interactions. Complex (2) makes a dinuclear structure by incorporating the chelating phen ligand, which is further interlinked via inter-molecular π···π stacking and C–H···π interactions to generate a higher-dimensional supramolecular network along the different crystallographic directions. The results reveal that the bulky anthracene ring skeleton in L, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of complexes (1) and (2). The magnetic properties of (1) and (2) were further investigated. As expected, the very long inter-metallic separations result in weak magnetic coupling, with the corresponding coupling constant values of J = −10 cm−1 for (1) and J = −2.46 cm−1 for (2). The constructions of two new MnII complexes comprising 1D chain (1) and dinuclear subunit (2) structures have been successfully achieved by using a bulky anthracene-9-carboxylic acid (HL), together with incorporating the chelating 1,10-phenanthroline as a co-ligand for (2). The result reveals that the bulky anthracene ring skeleton of HL, by virtue of intra- and/or inter-molecular π···π stacking and C–H···π interactions, plays an important role in the formation of the supramolecular architectures of (1) and (2). Moreover, magnetic properties of the complexes have been investigated.

Manganese(II) Complexes with a Bulky Anthracene-Based Dicarboxylic Ligand: Syntheses, Crystal Structures, and Magnetic Properties

To investigate the influence of the bulky aromatic ring skeleton with a large conjugated π-system on the structures and properties of its complexes, two MnII complexes with the anthracene-based dicarboxylic ligand anthracene-9,10-dicarboxylic acid (H2L) and different 2,2′-bipyridyl-like chelating ligands were synthesized and characterized: {[Mn2(L)2(bipy)2(H2O)2]}∞ (1) and {[Mn(L)(phen)2](H2O)2.5}∞ (2) (L = anthracene-9,10-dicarboxylate, bipy = 2,2′-bipyridine, and phen = 1,10-phenanthroline). Complex 1 has a (4,4) two-dimensional (2D) sheet structure that is further assembled to form a three-dimensional (3D) supramolecular network by the co-effects of C–H···π and O–H···O hydrogen-bonding interactions. Complex 2 adopts a one-dimensional (1D) polymeric chain structure by using the chelating phen instead of bipy in 1, which is further interlinked by interchain C–H···π interactions, which results in a higher-dimensional supramolecular network from the different crystallographic directions. The relevant results reveal that the steric bulk of the anthracene ring in H2L may play an important role in the formation of 1 and 2. Moreover, the magnetic properties of 1 and 2 show that the long Mn···Mn intermetallic separations result in weak magnetic coupling, along with the corresponding coupling constant J parameters related to their structural characteristics, –0.35 cm–1 for 1 and –3.0 cm–1 for 2.

Crystal and molecular structures of the organometallic species [Rh2(bim)2(cod)2]Cl2∙2H2O [bim=bis-(1-imidazolyl)methane; cod=1, 5-cyclooctadiene

The synthesis and X-ray powder diffraction data for the organometallic [Rh2(bim)2(cod)2]Cl2∙2H2O species are reported. Its crystal and molecular structures were determined by simulated annealing and full-profile Rietveld refinement methods. [Rh2(bim)2(cod)2]Cl2∙2H2O was found to crystallize in the orthorhombic Cmca space group. The lattice parameters were determined to be a=21.3574(6), b=10.7764(3), c=14.2795(4) Å, V=3286.5(2) Å3, for Z=4. The crystal structure was found to contain dimeric [Rh2(bim)2(cod)2]2+ cations, in which the bim ligands bridge Rh(cod) fragments with an intermetallic separation of ca. 8.90 Å. The crystal structure is completed by chloride ions and hydrogen-bonded water molecules, situated in the small cavities of the large cation substructure. The conformation of the bim ligand, lying on a crystallographic mirror plane, is rigorously Cs.