Metal-organic Coordination Complexes Research Articles

Syntheses, structures and properties of three lead(II) complexes constructed with 1,2,3,5-benzenetetracarboxylic acid

Three new lead(II) metal-organic coordination complexes constructed with tetracarboxyl tecton, namely, [Pb2(btec)] (1), [Pb3(µ4-O)(btec)(H2O)2]·H2O (2), and [Pb(btec)0.5(phen)] (3) (H4btec = 1,2,3,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline), have been prepared and characterized. A three-dimensional framework containing Pb(II) metal oxide sheet is being obtained in complex 1. Interestingly, a rather rare hexanuclear [Pb6(µ4-O2−)2]8+ octahedral core appeared in 2. The hexanuclear units are further connected by the btec4− ligands into a three-dimensional framework. When phen ligand was used as auxiliary coligand, a three-dimensional framework containing Pb2O2 dimer as building unit was observed in complex 3. Thermal stabilities and photoluminescent properties of complexes 1–3 have also been investigated.

Shielding effects of Fe3+-tannic acid nanocoatings for immobilized enzyme on magnetic Fe3O4@silica core shell nanosphere

Enzyme immobilization on solid supports is a valuable approach to address enzyme stability and reuse for continuous operations. However, the enzymes immobilized on the external surface of solid supports may not be protected by carriers and suffer inactivation caused by denaturing stresses and hazard external environment. Herein, we describe for the first time a enzyme-shielding strategy to prepare hybrid organic/inorganic nanobiocatalysts; it exploits the self-assembly of supramolecular metal-organic coordination complex (tannic acid (TA) and Fe3+) at the surface of immobilized catalase on Fe3O4/silica core-shell nanospheres to grow a protective nanocoating (Fe3+-TA nanocoating). The nanocoatings around the immobilized catalase (Fe3+-TA@Fe3O4/SiO2-catalase) provide a “shield effect” to protect from biological, thermal and chemical degradation for enzyme. As a result, the stability of immobilized catalase against proteolytic agent, denaturants and heat were improved remarkably compared to the immobilized catalase without a protective nanocoating and free catalase. More importantly, the recycling of the immobilized catalase was improved remarkably. The Fe3+-TA@Fe3O4/SiO2-catalase still retained 55% of their original activity after 9 cycles, whereas the immobilized catalase without a protective nanocoating only retained 20% of original activity. These results demonstrated that the novel enzyme-shielding strategy is an efficient method to obtain stable and recycled biocatalyst with yolk-shell structure.

Metal–Organic Coordination Complexes Serve the Electronic Industry as Low-Value Dielectric Constant Ferroelectric Material

Single crystals of praseodymium tartrate dihydrate possessing excellent ferroelectric, non-linear optical (NLO) properties and exhibiting remarkably flat habit faces are successfully grown by gel technique. The most predominant habit face is identified to be {101}. The dielectric behaviour recorded on {101} planes of single crystals exhibit a dielectric anomaly at 245°C, revealing a ferroelectric transition which is supported by thermal and polarisation versus electric field studies. The optical measurement leads to a band gap of 5.13 eV which is shown to be in good agreement with the studies of high-resolution x-ray diffraction (HRXRD), transport properties and NLO behaviour of the material. Absence of grain boundaries, thermal stability, ferroelectric and NLO behaviour supports the grown single crystal to find its place in microelectronic industry as a multifunctional material.

Synthesis, characterisation and catalytic activity of 4, 5-imidazoledicarboxylate ligated Co(II) and Cd(II) metal-organic coordination complexes

Two mono nuclear coordination complexes, namely, [Co(4,5-Imdc)2 (H2O)2] (1) and [Cd(4,5-Imdc)2(H2O)3]·H2O (2) were constructed using Co(II) and Cd(II) metal salts with 4,5-Imidazoledicarboxylic acid (4,5-Imdc) as organic ligand. Both 1, 2 were structurally characterized by single crystal XRD and the results reveal that 1 belongs to P21/n space group with unit cell parameters [a = 5.0514(3) Å, b = 22.5786(9) Å, c = 6.5377(3) Å, β = 111.5°] whereas, 2 belongs to P21/c space group with unit cell parameters [a = 6.9116(1) Å, b = 17.4579(2) Å, c = 13.8941(2) Å, β = 97.7°]. While Co(II) in 1 exhibited a six coordination geometry with 4,5-Imdc and water molecules, Cd(II) ion in 2 showed a seven coordination with the same ligand and solvent. In both 1 and 2, the hydrogen bond interactions with mononuclear unit generated 3D-supramolecular structures. Both complexes exhibit solid state fluorescent emission at room temperature. The efficacy of both the complexes as heterogeneous catalysts was examined in the green synthesis of six pyrano[2,3,c]pyrazole derivatives with ethanol as solvent via one-pot reaction between four components, a mixture of aromatic aldehyde, malononitrile, hydrazine hydrate and dimethyl acetylenedicarboxylate. Both 1 and 2 have produced pyrano [2,3,c]pyrazoles in impressive yields (92–98%) at room temperature in short interval of times (<20 min), with no need for any chromatographic separations. With good stability, ease of preparation and recovery plus reusability up to six cycles, both 1 and 2 prove to be excellent environmental friendly catalysts for the value-added organic transformations using green principles.

Artificial Spores: Immunoprotective Nanocoating of Red Blood Cells with Supramolecular Ferric Ion-Tannic Acid Complex.

The blood-type-mismatch problem, in addition to shortage of blood donation, in blood transfusion has prompted the researchers to develop universal blood that does not require blood typing. In this work, the “cell-in-shell” (i.e., artificial spore) approach is utilized to shield the immune-provoking epitopes on the surface of red blood cells (RBCs). Individual RBCs are successfully coated with supramolecular metal-organic coordination complex of ferric ion (FeIII) and tannic acid (TA). The use of isotonic saline (0.85% NaCl) is found to be critical in the formation of stable, reasonably thick (20 nm) shells on RBCs without any aggregation and hemolysis. The formed “RBC-in-shell” structures maintain their original shapes, and effectively attenuate the antibody-mediated agglutination. Moreover, the oxygen-carrying capability of RBCs is not deteriorated after shell formation. This work suggests a simple but fast method for generating immune-camouflaged RBCs, which would contribute to the development of universal blood.

Syntheses and characterization of three diphenyl phosphate based Cu(II) complexes and the effect of non-covalent interactions on their supramolecular framework

Assembly of diphenylphosphate (dpp) with Cu(II) salts in combination with the different N-donor linkers, e.g., pentamethyldiethylenetriamine (pmdeta), bis-(3-aminopropyl)amine (bapa) and 4-Picolene (4-pic), yielded three new metal-organic coordination complexes, namely {[Cu(dpp)(pmdeta)] ⋅ClO4.H2O}2 (1), {[{[Cu(dpp)(bapa)H2O] ⋅ClO4} (2) and [Cu(dpp)2(4-pic)2]2 (3) by stirring the constituent reactants at room temperature. Complexes 1–3 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD) studies. Compound 1 exhibits a dimeric Cu(II) complex which forms a 1D supramolecular chain along the crystallographic c-axis by means of intermolecular π…π interactions. Compounds 2 and 3 form a monomeric and dimeric complex of Cu(II) respectively, which are further extended into a supramolecular 2D structure via C-H.. π interactions for 2 and a 3D structure for 3 with the help of both intermolecular C-H.. π and π…π interactions for 3. In addition, the solid state UV-Vis spectra of compounds 1-3 and free dpp ligand have been investigated at room temperature. Three Cu(II) complexes based on diphenylphosphate (dpp) and different N-donor linkers, e.g., pentamethyldiethylenetriamine (pmdeta), bis-(3-aminopropyl)amine (bapa) and 4-Picolene (4-pic) were successfully synthesized and characterized. These complexes show fascinating supramolecular 1D, 2D and 3D structures by means of intermolecular π…π and C-H…π interactions additively or individually.

Thermally-induced single-crystal-to-single-crystal transformations from a 2D two-fold interpenetrating square lattice layer to a 3D four-fold interpenetrating diamond framework and its application in dye-sensitized solar cells.

In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal-organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO-LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3(-) and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs.

Diversity of Coordination Modes, Structures, and Properties of Chiral Metal–Organic Coordination Complexes of the Drug Voriconazole

AbstractFive chiral metal–organic coordination compounds (CMOCCs), {[Cu4O(Lvcz)2Br4]·H2O}n (1), {[Cd(HLvcz)2(NO3)2]·0.25H2O}n (2), {[Cu2(HLvcz)2I2]·H2O}n (3), {[Ag(HLvcz)2]CF3SO3}n (4), and {[Co2(HLvcz)(bdc)2(dmf)2]·dmf·3H2O}n (5; HLvcz = voriconazole, bdc = terephthalic acid), have been successfully prepared and structurally characterized. The chiral drug ligand voriconazole exhibits diverse modes of coordination in the five complexes, resulting in the formation of various architectures and properties. Complex 1 is a tetranuclear cluster, complex 2 exhibits a 1D double‐strand chain structure in which hydrogen‐bonding interactions lead to a 3D supramolecular network, complex 3 is a 1D chain structure with two different types of rings based on the rhombic dimer Cu2I2, complex 4 is a 2D structure with 63 topology that contains four types of C–H···F hydrogen bonds, and complex 5 affords a 3D framework with sxa topology. Their properties, such as chirality, second‐order nonlinear optical (NLO) effects, ferroelectric behavior and dielectric anomalies, have been investigated in the solid state.

Optical and surface studies of ligand based single crystal of tri-allylthiourea cadmium chloride

Metal–organic coordination complex crystal triallylthiourea cadmium chloride has been synthesized by slow evaporation technique. The grown crystals were characterized by single crystal and powder X-ray diffraction analysis. The second harmonic generation measurement confirms that the crystal has nonlinear optical property. The spectroscopic studies revealed that the grown crystal has good optical transparency. The functional groups have been identified using infrared spectrum. The mechanical strength of the grown crystal was found from Vickers micro hardness measurement and the thermal stabilities were determined with the aid of thermo gravimetric analysis and differential thermal analysis. The surface morphology was studied by using field emission scanning electron microscope and atomic force microscopy.

Mechanistic Studies of Transition Metal‐Terephthalate Coordination Complexes upon Electrochemical Lithiation and Delithiation

Redox‐active organic molecules are intriguing candidates as active electrode materials for next‐generation rechargeable batteries due to their structural diversity, environmental friendliness, and solution‐phase preparation processes. Recently, a transition metal–organic coordination approach is exploited to construct high capacity anodes for lithium‐ion rechargeable batteries. Here, a family of transition metal–organic coordination complexes with terephthalate ligands is synthesized that exhibit reversible capacities above 1100 mA h g−1. The reaction mechanism to describe the multi‐electron redox processes is investigated at the molecular‐level via the synchrotron‐sourced X‐ray absorption spectroscopy and solid‐state NMR analyses. The spectroscopic studies reveal that the electrochemical process involves oxidation state changes of the transition metals followed by additional lithium insertion/extraction in the conjugated aromatic ligands. The combined approaches assisted by synthetic organic chemistry and solid‐state analysis provide mechanistic insights into excessive lithiation processes that have implications for the design of high‐performance anode materials.

Sodium Chloride Dihydrate Crystals: Morphology, Nucleation, Growth, and Inhibition

Sodium chloride powders have a strong tendency to cake at freezing temperatures, which is caused by the formation of sodium chloride dihydrate solid bridges between the powder particles. Using the crystallographic structure, the morphology of the dihydrate crystals was determined. In addition, the growth rate of the most important facets of these crystals was measured as well as the influence of a number of anticaking agents and related additives on the growth rate. A likely candidate for the inhibition of dihydrate growth was found: a mixture of iron(III) and l-tartaric acid, which probably forms a metal–organic coordination complex. The nucleation rate of the dihydrate was found to be extremely low and to increase with time. This is probably caused by the formation of a metastable prenucleation phase, which inhibits the nucleation of dihydrate crystals. The influence of the additives on the nucleation rate was found to be limited.

Assembly and photocatalysis of three novel metal–organic frameworks tuned by metal polymeric motifs

By using a thiodiacetate, phenanthroline, and tuning the metal salts in the reaction system, three new metal–organic coordination complexes, {[Co(MOPIP)2(tda)]·H2O}1∕2 (1), [Cd(MOPIP)2(tda)]2·3H2O (2), and [Cu5I4(MOPIP)3·H2O]n (3) (, thiodiacetate; MOPIp = 2-(4-methoxyphenyl)-1H-imidazo[4,5-f][1, 10]phenanthroline), have been prepared through hydrothermal reactions. In 1 and 2, the metal (Co2+/Cd2+) centers are connected by tda to form a mononuclear molecule, which connect to a two-dimensional (2-D) layer by N–H⋯O hydrogen bonds. By selecting the copper iodide salt we get 3, where the Cu+ center exhibits three different coordination types, which has never been seen before in the same compound, and linked by iodide and MOPIP to construct a new 3-D framework. Compound 3 represents the first example of MOPIP showing a new coordination mode with four nitrogens all coordinated. The metal salts play an important role in assembly of the structures of 1–3. Introduction of MOPIP shows significant effect on the dimensionalities of complexes. The fluorescence and catalytic properties of 1 and 3 have also been investigated.

Heterogeneous Catalysis of Polyoxometalate Based Organic-Inorganic Hybrids.

Organic–inorganic hybrid polyoxometalate (POM) compounds are a subset of materials with unique structures and physical/chemical properties. The combination of metal-organic coordination complexes with classical POMs not only provides a powerful way to gain multifarious new compounds but also affords a new method to modify and functionalize POMs. In parallel with the many reports on the synthesis and structure of new hybrid POM compounds, the application of these compounds for heterogeneous catalysis has also attracted considerable attention. The hybrid POM compounds show noteworthy catalytic performance in acid, oxidation, and even in asymmetric catalytic reactions. This review summarizes the design and synthesis of organic–inorganic hybrid POM compounds and particularly highlights their recent progress in heterogeneous catalysis.

Combined experimental and theoretical investigation of characterization and hydrogen storage properties of Zn(II) based complex and composites

Metal organic structured coordination complex was synthesized by using Zn(II), 1,10 Phenantroline and teraphtalic acid building blocks. Then the synthesized compound have been characterized with Ft-IR, TGA/DTA/DrTGA, EA, SEM, surface area analysis and PXRD techniques. After that, the composites have been prepared with the Pt loaded activated carbon additive. Also, all the adsorbents were simulated by using Materials Studio 7.1 (MS); Amorphous Cell module and Atom volumes & Surfaces tool as a visualizer. Then hydrogen storage properties of simulated adsorbents were calculated by using the Sorption module of MS. It is found that the compound and its composites could uptake hydrogen with the capacity in 0.4–0.6 wt.% range experimentally at 77 K and 1 bar pressure while the range was 0.25–0.50 wt.% theoretically at the same conditions. Maximum hydrogen uptake have been observed by using additive free compound which was 0.594 wt.% experimentally at 77 K and 1 bar. Simulated hydrogen adsorption performances were 0.51 and 0.57 wt.% at 77 K, 1 and 100 bar respectively for additive free compound.

A 3-fold interpenetrating 3D Cu(II) coordination polymer based on a semi-rigid naphthalene-based bis-pyridyl-bis-amide and thiophene-2,5-dicarboxylate

A new 3D Cu(II) coordination polymer [Cu2(4-dpna)2(2,5-tdca)2] (1) (4-dpna=N1,N4-di(pyridin-4-yl)naphthalene-1,4-dicarboxamide, 2,5-H2tdca=thiophene-2,5-dicarboxylic acid) has been hydrothermally synthesized. Complex 1 is a novel 3D metal–organic coordination complex based on a semi-rigid naphthalene-based bis-pyridyl-bis-amide ligand, which shows a 3-fold interpenetrating network with a CdSO4-like topology. Moreover, the fluorescent property, electrochemical behavior and selective photocatalytic activity of 1 have been investigated.

ChemInform Abstract: Self‐Assembled Discrete Metal‐Organic Complexes: Recent Advances

AbstractReview: 181 refs.

Synthesis, crystal structures and characterization of three cadmium(II) metal–organic coordination complexes constructed from flexible bis(imidazole) and carboxybenzaldehyde ligands

Three new cadmium(II) coordination complexes, namely, [Cd2(1,2-bix)4(L)4]n (1), [Cd(1,3-bix)(L)2]n·H2O (2), [Cd(1,4-bix)(L)2H2O)]n·2.5H2O (3) have been synthesized using 4-carboxybenzaldehyde (HL) and 1,n-bis(imidazol-l-ylmethyl)benzene (1,n-bix; n=2, 3, 4) as ligands. These complexes were structurally characterized by single-crystal X-ray crystallography and further characterized by FT-IR spectroscopy and thermogravimetric analysis (TGA). Complex 1 is a binuclear, complex 2 possesses a 1D double chain. Compound 3 features a 1D zigzag chain, assembled into a 2D layer structure by weak π–π interactions. The photoluminescent properties of the compounds 1–3 were also investigated.

Five copper(ii) metal–organic coordination complexes with micro-channels based on flexible bis(imidazole) and carboxybenzaldehyde ligands; structural influence of experimental conditions on their frameworks

Five new copper(II) metal–organic coordination complexes, [Cu2(1,2-bix)2(L)4] (1), [Cu(1,3-bix)(L)2]n·nCH3OH·3H2O (2), [Cu(1,3-bix)(L)2]n·nH2O (3), [Cu5(1,3-bix)2(L)6(NO3)2(H2O)2(OH)2]·2H2O (4) and [Cu(1,4-bix)(L)2]n (5), have been synthesized using 4-carboxybenzaldehyde (HL) and 1,n-bis(imidazol-l-ylmethyl)benzene (1,n-bix; n = 2, 3, 4) as ligands. These complexes were structurally characterized by single-crystal X-ray crystallography and further characterized by FT-IR spectroscopy and thermogravimetric analysis (TGA). Complex 1 is a symmetrical binuclear structure, and in compound 2 the 1D ladders are entangled through π–π stacking interactions to generate a 3D network with one-dimensional micro channel. A 3D coordination framework 2 converted to network 3 by just increasing the reaction temperature. Metal–organic polymer 3 is comprised of 1D corrugated double chains structure. Complex 4 has a pentanuclear (Cu5) cluster structure and compound 5 shows a 1D zigzag chain. The magnetic properties of the complexes 1 and 3 are reported briefly.

Hydrothermal synthesis, crystal structure, and properties of two novel binuclear complexes based on Zaltoprofen and 2,2′-bipyridine ligands

Two novel binuclear metal-organic coordination complexes [M2(Zaltoprofen)2(Bipy)2] [M = Cd (I), Zn (II); Zaltoprofen = 5-(1-carboxyethyl)-2-(phenylthio)phenylacetic acid, Bipy = 2,2′-bipyridine) have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR and electronic spectroscopy, powder X-ray diffraction, and fluorescent properties. Complexes I, II crystallize isomorphously in the monoclinic space group P21/c. Structural analysis shows that the M(II) atom of I and II is coordinated with four oxygen atoms from the carboxyl group of the Zaltoprofen together with two nitrogen atoms from the Bipy. The 3D structures of the complexes are stabilized by π-π stacking interactions.

Synthesis, structures and properties of two metal-organic coordination polymers derived from manganese(ΙΙ), thiabendazole and polydentate carboxylic acids.

Two novel binuclear Mn(II) metal-organic coordination complexes [Mn2(TBZ)2(CDC)(C2O4)]n (1), {[Mn2(TBZ)2(BDC)0.5(BTC)(H2O)2]·ET}n (2), (where TBZ = thiabendazole, H2CDC = trans-1,4-cyclohexanedicarboxylic acid, H2C2O4 = oxalic acid, H3BTC = 1,3,5-benzenetricarboxylic acid, ET = ethanol, H2BDC = 1,4-benzenedicarboxylate) have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, electrochemical analysis and single crystal X-ray diffraction. The X-ray structure analysis reveals that 1 is s two-dimensional layer and 2 is s one-dimensional chain. In complex 1, it reveals 2-D layers composed of multi-(bidentate) bridging ligands (CDC and C2O4), and in 2, the coordinated BTC ligands adopt a monodentate mode and with BDC ligands adopt alternately chelating Mn1 and Mn2 bridges into 1-D chains. The 3-D structures of the two complexes are stabilized by π-π stacking interactions and hydrogen bonds.