Crystal engineering of Cu-containing metal–organic coordination polymers under hydrothermal conditions

Ionic liquids: new perspectives for inorganic synthesis?

Ionic liquids are credited with a number of unusual properties. These include a low vapor pressure, a wide liquid-phase range, weakly coordinating properties, and a high thermal/chemical stability. These properties are certainly of great interest for inorganic synthesis and the creation of novel inorganic compounds. On the other hand, the synthesis repertoire for preparing inorganic compounds has always been broad, ranging from syntheses in solutions and melts to solid-state reactions, and from crystal growth in the gas phase to high-pressure syntheses. What new aspects can ionic liquids then add to the synthesis of inorganic compounds? This Minireview uses some early examples to show that the use of ionic liquids indeed provides access to unusual inorganic compounds.

In Situ Synthesis, X-Ray Structure, Fluorescence and Theoretical Investigations of [Cu2Cl4][(C2H5)2-4,4'-Bipyridine]

A novel N,N'-diethyl-4,4'-bipyridine copper complex, [Cu2Cl4][(C2H5)2-4,4'-bipyridine] (1), has been obtained in situ through a solvothermal reaction and structurally characterised by X-ray diffraction. Complex 1 comprises discrete Cu2Cl4 moieties and (C2H5)2-4,4'-bipyridine molecules interlinked via hydrogen bonding interactions to give a three-dimensional supramolecular open framework. Photoluminescent study shows that the complex exhibits an emission in the green region. Theoretical study reveals that the emission is attributed to the π → π* charge-transfer interaction of the (C2H5)2-4,4'-bipyridine moieties.

In Situ Synthesis, Structure, Photoluminescence and Theoretical Study of [Cu(2-PyCOOH)2(H2O)2]Cl2

A new pyridine-2-carboxylic acid complex, [Cu(2-PyCOOH)2(H2O)2]Cl2, has been prepared in situ through a hydrothermal reaction and its structure comprises discrete [Cu(2-PyCOOH)2(H2O)2]2+ cations and chloride anions which are interlinked via hydrogen bonding interactions to give a 3-D supramolecular motif. Photoluminescent study shows that the complex exhibits an emission in the blue region. Theoretical studies reveal that the emission can be ascribed to metal-to-ligand charge transfer.

A novel three-dimensional heterometallic coordination polymer: poly[[diaquadi-μ3-chlorido-μ2-chlorido-tri-μ3-nicotinato-tricopper(I)gadolinium(III)] hemihydrate]

In the title polymeric heterometallic compound, {[Cu(3)Gd(C(6)H(4)NO(2))(3)Cl(3)(H(2)O)(2)]·0.5H(2)O}(n), comprising copper(I) and gadolinium(III) cations bridged by nicotinate (nic) ligands and chloride anions, the Gd(III) centers display a bicapped trigonal prismatic geometry, defined by six carboxylate O atoms and two water molecules. For copper(I), one Cu center is three-coordinated by three chloride ions and displays a trigonal-planar geometry; the other two Cu centers are four-coordinated and display a very distorted tetrahedral geometry. The chloride anions act in μ(2)- and μ(3)-bridging modes, linking the Cu(I) ions into an infinite chain. The nic ligand exhibits a tridentate coordination mode, with the carboxylate O atoms linking to two Gd(III) ions and the N atom linking to one Cu(I) ion. Thus, a novel three-dimensional heterometallic coordination polymer is constructed from Gd-carboxylate subunits and Cu-Cl chains. In addition, intra- and intermolecular O-H···O and O-H···Cl hydrogen bonds are also observed within the three-dimensional structure. Topologically, the framework represents an unusual 3,6-connected (4.8(2))(3)(4(10).6(5)) net.

The first metal-organic framework containing an unprecedented in situ-generated C-substituted hexamethylenetetramine ligand

The first metal-organic framework containing an unprecedented in situ-generated C-substituted hexamethylenetetramine ligand has been successfully prepared by the reaction of silver nitrate, 4-formylbenzoic acid and hexamethylenetetramine under traditional solution conditions, which holds the unusual (3,4)-connected topological network.

Crystal structure of an oxalate-bridged tetranuclear 8-hydroxyquinoline Zn(II) cluster: [Zn4Q6(Ox)]0.5n

The chain structure of a tetranuclear zinc(II) cluster [Zn4Q6(Ox)]0.5n ([Zn4 (C9H6NO)6(C2O4)]0.5n) (1) (Q = 8- hydroxyquinoline anion, Ox = oxalate dianion) was determined by X-ray crystallography and characterized by elemental analysis, IR spectroscopy and thermal analysis. It crystallizes in the monoclinic system, space group P21/n (No. 14), with the lattice parameters a = 13.2222(15) ?, b = 11.0566(12) ?, c = 16.2224(18) ?, ? = 92.1770(10)?, V = 2369.9(5) ?3, Z = 4, Mr = 607.23 g mol-1, Dc = 1.702 g cm-3. The tetranuclear zinc(II) clusters form 1D polymeric chains parallel to the b-axis. The ?-? stacking interactions involving aryl rings support the formation of the 1D polymeric structure. The neighboring polymeric chains are connected by C-H???? interactions.

Synthesis, Structure and Photoluminescence of [N-ethyl-4,4′-bipyridinium][CdBr4] with N-ethyl-4,4′-bipyridinium Generated in situ

A new viologen(4,4′-bipyridinium)-based complex [ N-ethyl-4,4′-bipyridinium][CdBr4], in which N-ethyl-4,4′-bipyri-dinium ( EQ2+) has been generated in situ, has been synthesised via hydrothermal reaction and structurally characterised by single-crystal X-ray diffraction. [ N-ethyl-4,4′-bipyridinium][CdBr4] features an isolated structure, based on an N-ethyl-4,4′-bipyridinium moiety and a cadmium atom terminally bound by four bromine atoms. Photoluminescence investigation reveals a broad and intense emission in blue region, which may originated from π → π* charge-transfer interaction of the N-ethyl-4,4′-bipyridinium moiety.

Heterobimetallic metal-complex assemblies constructed from the flexible arm-like ligand 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene: structural versatility in the solid state

The bidentate ferrocenyl sandwich molecule 1,1'-bis[(3-pyridylamino)carbonyl]ferrocene (3-BPFA) has been employed as an organometallic ligand in reactions with a series of transition metal salts to construct heterobimetallic architectures. X-ray crystallographic characterization reveals that the crystal packing of free ligand 3-BPFA induces spontaneous resolution of helical chains via intermolecular hydrogen bonds. By combining the flexibility from the arm-like molecule (3-BPFA) with the variation of the coordination property from different metal ions and/or the different counteranions, five different types of architectures are prepared: one octahedral coordination cage (copper(II) complex 1); two discrete pseudocapsules for combination of chlorine anions (nickel(II) complex 2 and cobalt(II) complex 3); two dimers with metal-metal interactions (silver(I) complexes 4 and 5); one macrocyclic complex (mercury(II) complex 6); and five two-dimensional mixed-metal-organic frameworks (M'-MOFs) (zinc(II), cadmium(II), and mercury(II) complexes 7-11). The structures of all complexes are characterized in detail by IR, elementary analysis, and single-crystal X-ray diffraction analysis. The factors inducing the structure variation among the complexes are discussed by taking account of the coordination geometry of different metal ions, the span angle between the two "arms", and the coordination mode of the 3-BPFA ligand.

Poly[trans-diaquabis[μ-3-(3-pyridyl)propionato-κ2N,O]cadmium(II)]

The title compound [Cd(L)₂(H₂O)₂]_n (L = 3-pyridine­propionic acid, C₈H₈NO₂), is a two-dimensional coordination polymer in which the Cd^II ion lies on an inversion center and is coordinated in a slightly distorted octa­hedral environment. The aqua H atoms are involved in inter­molecular O–H⋯O hydrogen bonds, which extend the two-dimensional structure to a three-dimensional architecture. The Cd⋯Cd separation within a layer is 9.0031 (1) Å.

Dynamic combinatorial chemistry in a solvothermal process of Cu(I,II) and organosulfur ligands

An unprecedented microwave C(sp(2))-S and S-S bond activation of 2,2'-dipyridyldisulfide (2-dpds) and the formation of a new architecture of coordination networks obtained by reaction of Cu(HCO(2))(2).xH(2)O with 2-dpds under solvothermal microwave conditions are reported. This unusual reaction proceeds with the partial oxidation of 2,2'-dipyridyldisulfide to sulfate. The process generates: a Cu(I) dimetallic complex [Cu(2)(mu-Hpyt)(2)(Hpyt)(4)](SO(4)).approximately 5EtOH (1), a Cu(I,II) polycationic coordination polymer [Cu(H(2)O)(6)][Cu(6)(mu-Hpyt)(12)](SO(4))(4).4H(2)O (2) and a dimetallic Cu(II) complex [Cu(2-dps)(mu-SO(4))(H(2)O)](2).3H(2)O (3). It is worth mentioning the strong red luminescence shown by compounds 1 and 2.