Syntheses, structures, and magnetic properties of three supramolecular isomeric Cu(ii) square grid networks: solvents effect on the ligand linkages

Three supramolecular isomeric Cu(ii) networks with different metal fragments and ligand conformations were obtained by the adjustment of solvent molecules.

Construction and photoluminescence properties of a three-dimensional ZnII coordination network based on naphthalene-1,4-dicarboxylic acid and 1,6-bis(pyridin-3-yl)-1,3,5-hexatriene

In recent years, coordination polymers constructed from multidentate carboxylate and pyridyl ligands have attracted much attention because these ligands can adopt a rich variety of coordination modes and thus lead to the formation of crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[μ₂-1,6-bis(pyridin-3-yl)-1,3,5-hexatriene-κ²N:N'](μ₃-naphthalene-1,4-dicarboxylato-κ⁴O¹,O^1':O⁴:O^4')zinc(II)], [Zn(C₁₂H₆O₄)(C₁₆H₁₄N₂)]_n, has been prepared by the self-assembly of Zn(NO₃)₂·6H₂O, naphthalene-1,4-dicarboxylic acid (1,4-H₂ndc) and 1,6-bis(pyridin-3-yl)-1,3,5-hexatriene (3,3'-bphte) under hydrothermal conditions. The title compound has been structurally characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. Each Zn^II ion is six-coordinated by four O atoms from three 1,4-ndc^2- ligands and by two N atoms from two 3,3'-bphte ligands, forming a distorted octahedral ZnO₄N₂ coordination geometry. Pairs of Zn^II ions are linked by 1,4-ndc^2- ligands, leading to the formation of a two-dimensional square lattice (sql) layer extending in the ab plane. In the crystal, adjacent layers are further connected by 3,3'-bphte bridges, generating a three-dimensional architecture. From a topological viewpoint, if each dinuclear zinc unit is considered as a 6-connected node and the 1,4-ndc^2- and 3,3'-bphte ligands are regarded as linkers, the structure can be simplified as a unique three-dimensional 6-connected framework with the point symbol 4⁴6¹⁰8. The thermal stability and solid-state photoluminescence properties have also been investigated.

Construction of a three-dimensional supramolecular framework based on an anionic cadmium(II) coordination network and protonated dipyridine organic cations

As a class of multifunctional materials, crystalline supramolecular complexes have attracted much attention because of their unique architectures, intriguing topologies and potential applications. In this article, a new supramolecular compound, namely catena-poly[4,4'-(buta-1,3-diene-1,4-diyl)dipyridin-1-ium [(μ₄-benzene-1,2,4,5-tetracarboxylato-κ⁶O¹,O^1':O²:O⁴,O^4':O⁵)cadmium(II)]], {(C₁₄H₁₄N₂)[Cd(C₁₀H₂O₈)]}_n or {(1,4-H₂bpbd)[Cd(1,2,4,5-btc)]}_n, has been prepared by the self-assembly of Cd(NO₃)₂·4H₂O, benzene-1,2,4,5-tetracarboxylic acid (1,2,4,5-H₄btc) and 1,4-bis(pyridin-4-yl)buta-1,3-diene (1,4-bpbd) under hydrothermal conditions. The title compound has been structurally characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. Each Cd^II centre is coordinated by six O atoms from four different (1,2,4,5-btc)^4- tetraanions. Each Cd^II cation, located on a site of twofold symmetry, binds to four carboxylate groups belonging to four separate (1,2,4,5-btc)^4- ligands. Each (1,2,4,5-btc)^4- anion, situated on a position of -1 symmetry, binds to four crystallographically equivalent Cd^II centres. Neighbouring Cd^II cations interconnect bridging (1,2,4,5-btc)^4- anions to form a three-dimensional {[Cd(1,2,4,5-btc)]^2-}_n anionic coordination network with infinite tubular channels. The channels are visible in both the [1-10] and the [001] direction. Such a coordination network can be simplified as a (4,4)-connected framework with the point symbol (4²8⁴)(4²8⁴). To balance the negative charge of the metal-carboxylate coordination network, the cavities of the network are occupied by protonated (1,4-H₂bpbd)²⁺ cations that are located on sites of twofold symmetry. In the crystal, there are strong hydrogen-bonding interactions between the anionic coordination network and the (1,4-H₂bpbd)²⁺ cations. Considering the hydrogen-bonding interactions, the structure can be further regarded as a three-dimensional (4,6)-connected supramolecular architecture with the point symbol (4²6⁴)(4²6⁸7·8⁴). The thermal stability and photoluminescence properties of the title compound have been investigated.

A two-dimensional CdII coordination polymer based on naphthalenediimide: synthesis, crystal structure and photochromic properties

Naphthalenediimides, a class of organic dyes with an expanded π-electron-deficient plane, have attracted considerable interest because of their photoinduced electron transfer from neutral organic moieties to stable anionic radicals. This makes them excellent candidates for organic linkers in the construction of photochromic coordination polymers. Such a photochromic two-dimensional coordination polymer has been prepared using N,N'-bis(pyridin-4-ylmethyl)naphthalene-1,8:4,5-bis(dicarboximide) (DPMNI). In crystallization tubes, upon slow diffusion of an MeOH solution of cadmium perchlorate into a CHCl₃ solution of DPMNI, the complex poly[[bis[μ₂-2,7-bis(pyridin-4-ylmethyl)benzo[imn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetrone-κ²N:N']bis(perchlorato-κO)cadmium(II)] chloroform tetrasolvate], {[Cd(C₂₆H₁₆N₄O₄)₂(ClO₄)₂]·4CHCl₃}_n, (I), was obtained. The asymmetric unit contains one Cd²⁺ cation, two DPMNI ligands, two coordinated ClO₄^- anions and four CHCl₃ solvent molecules. Each Cd²⁺ cation is interconnected by four DPMNI linkers to generate a neutral two-dimensional naphthalenediimide coordination network with all the ClO₄^- anions above or below this plane. Strong interlaminar anion-π interactions between the coordinated ClO₄^- anions and the imide rings of an adjacent layer lead to a three-dimensional supramolecular structure. Compound (I) exhibits reversible photochromic behaviour and photocontrolled tunable luminescence properties, which may originate from the photoinduced electron-transfer generation of radicals in the DPMNI ligand.

A three-dimensional supramolecular framework based on the interlinkage of an interpenetrating diamondoid coordination network

In the development of coordination-driven crystalline materials, O- and N-atom donors from carboxylate and pyridyl-based ligands are widely used classes of multidentate bridging ligands composed of several terminal coordinating groups linked by either rigid or flexible spacers. The rigidity of the ligands can play a vital role in the determination of the structures formed. A new Cd^II supramolecular compound, namely poly[μ-adipato-κ²O¹:O⁴-μ-adipato-κ⁴O¹,O^1':O⁴,O^4'-diaquabis[μ-1,4-bis(pyridin-4-yl)-1,3-butadiene-κ²N:N']dicadmium(II)], [Cd₂(C₆H₈O₄)₂(C₁₄H₁₂N₂)₂(H₂O)₂]_n, (I), has been synthesized by the self-assembly of Cd(NO₃)₂·4H₂O, adipic acid (hexane-1,6-dioic acid; H₂adp) and the dipyridyl ligand 1,4-bis(pyridin-4-yl)buta-1,3-diene (1,4-bpbd) under hydrothermal conditions. Single-crystal X-ray diffraction analysis reveals that each Cd^II centre is located in a distorted octahedral coordination environment, coordinated by one water O atom, three carboxylate O atoms from two different adp^2- ligands and two N atoms from two different 1,4-bpbd ligands. The Cd(H₂O) units are interconnected by the μ₂,κ²-adp^2-, μ₂,κ⁴-adp^2- and 1,4-bpbd ligands, which lie across centres of inversion, to give a 6⁶-dia network. Large cavities within a single diamondoid network permit the mutual threefold interpenetration of crystallographically equivalent frameworks. Hydrogen-bonding interactions between the coordinated water molecules and adp^2- carboxylate O atoms anchor the interpenetrating networks into a unique three-dimensional supramolecular structure. Topologically, taking the coordinated water molecules and Cd^II centres as nodes, the whole architecture can be simplified as a binodal (3,7)-connected supramolecular framework. The identity of (I) was further characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis and powder X-ray diffraction. The solid-state photoluminescence properties of (I) were also investigated.

Six new coordination compounds based on rigid 5-(3-carboxy-phenyl)-pyridine-2-carboxylic acid: synthesis, structural variations and properties

Compounds 1–6 have rich structural chemistry ranging from mononuclear (1 and 2), one-dimensional (3 and 4), two-dimensional (5) to three-dimensional (6) structures.

Photochromic and Nonphotochromic Luminescent Supramolecular Isomers Based on Carboxylate-Functionalized Bipyridinium Ligand: (4,4)-Net versus Interpenetrated (6,3)-Net

Photochromic and nonphotochromic luminescent bipyridinium-based supramolecular isomers [Cd(CPBPY)(BDC)(H2O)]n (1) and {[Cd(CPBPY)(BDC)]·H2O}n (2) (CPBPY = N-(3-carboxyphenyl)-4,4'-bipyridinium, BDC= terephthalate) have been successfully obtained by solvothermal reactions at 100 °C via tuning stoichiometric ratios of starting reagents. Isomer 1 features (4,4)-topological layer constructed by edge-shared Cd2 SBUs and BDC linkers attached by N-pendent CPBPY groups. Isomer 2 has (6,3)-topological layers with Cd atoms as nodes and BDC and double CPBPY as linkers, which are 4-fold interpenetrated into 3D network. Although both 1 and 2 contain bipyridinium ligands, only isomer 1 possesses reversible photochromic behavior with quick-switchable luminescence in the solid state. Compound 2 does not show photochromic behavior even after exposure to UV light for more than 2 h. Photochromism process of 1 originates from photostimulated reduction of CPBPY ligands to generate CPBPY(•-) radicals after irradiation, confirmed by EPR spectra. Careful check on structure reveals that the offset π-π stacking interaction between the pyridine ring of CPBPY and benzene ring of BDC with inter-ring shortest C···C distance of 3.214 Å in 1 is responsible for electron transfer to form the CPBPY(•-) radicals. The speculation is further supported by DFT calculation of frontier orbital matching of electron donor and acceptor. HOMO and HOMO-2 orbitals of BDC involve the carbon atoms of benzene ring while LUMO and LUMO+1 orbitals of CPBPY involve the carbon atoms of pyridinium ring. Importantly, the photoinduced formed CPBPY(•-) radicals in 1 have a long-lived lifetime (at least six months in air and room temperature condition), which is mainly attributed to the close packing mode.