Synthesis and characterization of redox-active coordination polymers generated from ferrocene-containing bridging ligands

Coordination polymers showing redox activity have been constructed by using ferrocene-based bidentate ligands, 1,1'-(4-dipyridinethio)ferrocene (1) and 1,1'-(2-dipyridinethio)ferrocene (2). The ligand of 1 formed an Ag(I) coordination polymer, 1 x AgPF(6) x (CH(3)CN)(2) (3). This complex showed a 1-D double-chain structure, with a weak interchain Ag...Ag interaction. Combination of 1 with M(hfac)(2) (M = Mn, Cu, Zn) afforded 1-D chain complexes, 1 x M(hfac)(2) (M = Mn (5), Cu (6), Zn (7)). The complex 2 x CuPF(6) (8) showed a 1-D twisted helix-like chain structure.     

Ditopic hydridoborates and hydridoboranes: bridging ligands in coordination polymers and versatile hydroboration reagents

Single crystals of the meta- and para-phenylene-bridged ditopic trihydridoborates (Li(THF)(2))(2)[m-C(6)H(4)(BH(3))(2)] and (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)] have been prepared and investigated by X-ray crystallography. The compounds turned out to be coordination polymers in which each trihydridoborate substituent is connected with one trihydridoborate substituent of a neighbouring monomer via two bridging Li(THF)(2)(+) ions. (Li(THF)(2))(2)[m-C(6)H(4)(BH(3))(2)] and (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)] suffer from poor solubility in all common non-protic solvents. Thus, a more soluble derivative of (Li(THF)(2))(2)[p-C(6)H(4)(BH(3))(2)], equipped with n-hexyl groups at the positions 2 and 5 of the phenylene ring, has been used for all further investigations (i.e., compound Li(2)[6]). Treatment of Li(2)[6] with Me(3)SiCl in the presence of excess N(Me)(2)Et leads to the abstraction of one hydride ion per boron atom under formation of the ditopic amine-borane adduct p-C(6)H(2)(n-hexyl)(2)(BH(2)-N(Me)(2)Et)(2) (7). The compound turned out to be an efficient hydroboration reagent both for internal olefins (i.e., 1,5-cyclooctadiene) and terminal alkynes (i.e., tert-butyl acetylene) to give p-C(6)H(2)(n-hexyl)(2)(9-BBN)(2) (8; 9-BBN = 9-borabicyclo[3.3.1]nonyl) and p-C(6)H(2)(n-hexyl)(2)(B(C(H)=C(H)tBu)(2))(2) (9), respectively.     

Supramolecular architectures and magnetic properties of coordination polymers based on pyrazinedicarboxylato ligands showing embedded water clusters

The synthesis, crystal structure, and magnetic behavior of nine transition-metal complexes based on pyrazine-2,5-dicarboxylato (pz25dc) and pyrazine-2,3-dicarboxylato (pz23dc) ligands are reported. The pz25dc ligand displays a bis-bidentate coordination mode, with the carboxylate groups almost coplanar with the pyrazine ring, to afford polymeric 1-D chains [Mn(1), Fe(2), Zn(3), and Cu(4 and 5)] and discrete dimeric entities [Mn(6)] when the 1,10-phenanthroline (phen) blocking ligand is used to avoid further polymerization. The nonplanar pz23dc ligand chelates to a unique copper center, while it bridges another one or two metal centers via the remaining carboxylate group, leading to 1-D polymeric chains (7), ladder chains (8), and sheets (9). The crystal packing of the metal-organic frameworks of compounds 4-9 generates voids which are occupied by assembled water molecules. The different water cluster patterns (tapes, four-membered discrete rings, and chains for compounds 6, 8, and 9, respectively) and their role in the cohesiveness of supramolecular architectures are analyzed. Thermogravimetric and variable-temperature X-ray powder diffraction studies have revealed the occurrence of reversible dehydration processes in compounds 6, 8, and 9. Furthermore, the magnetic behavior of these compounds has been studied in order to analyze the capability of the pyrazine ring to transmit magnetic interactions.     

Two different one‐dimensional CdII halide coordination polymers constructed through bridging carboxylate ligands

Two cadmium halide complexes, catena‐poly[[chloridocadmium(II)]‐di‐μ‐chlorido‐[chloridocadmium(II)]‐bis[μ₂‐4‐(dimethylamino)pyridin‐1‐ium‐1‐acetate]‐κ³O:O,O′;κ³O,O′:O], [CdCl₂(C₉H₁₂N₂O₂)]_n, (I), and catena‐poly[1‐cyanomethyl‐1,4‐diazoniabicyclo[2.2.2]octane [[dichloridocadmium(II)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′] monohydrate], {(C₈H₁₅N₃)[CdCl₂(C₂O₄)]·H₂O}_n, (II), were synthesized in aqueous solution. In (I), the Cd^II cation is octahedrally coordinated by three O atoms from two carboxylate groups and by one terminal and two bridging chloride ligands. Neighbouring Cd^II cations are linked together by chloride anions and bridging O atoms to form a one‐dimensional zigzag chain. Hydrogen‐bond interactions are involved in the formation of the two‐dimensional network. In (II), each Cd^II cation is octahedrally coordinated by four O atoms from two oxalic acid ligands and two terminal Cl⁻ ligands. Neighbouring Cd^II cations are linked together by oxalate groups to form a one‐dimensional anionic chain, and the water molecules and organic cations are connected to this one‐dimensional zigzag chain through hydrogen‐bond interactions.     

Binding sites on the outside of metallo-supramolecular architectures; engineering coordination polymers from discrete architectures

Aggregation of metallo-supramolecular architectures through additional coordination is explored by introducing metal-binding units onto the outside of the supramolecular architectures. This is achieved within the framework of our imine-based approach to supramolecular architecture, by replacing the pyridylimine units with pyrazylketimine units. An advantage of the design is that it retains the ease-of-synthesis which characterises our imine-based approach. Silver(I) complexes of three pyrazylketimine ligand systems are described. The complexes demonstrate that introducing pyrazine donor units does indeed allow higher-order assembly of the distinct supramolecular architectures into engineered coordination polymers. Two distinct types of aggregation are observed. In the first, the donors on the outside of one architecture bind to the metals of another to link the units into a polymeric array. In the second type, the donors on the outside of the architectures bind to separate metal centres which are themselves not part of the architectures, and these separate metal centres link the units to form the macromolecular array. The weaker donor nature of the pyrazine nitrogens (compared to pyridine) also introduces an additional element into the design; higher coordination numbers are favoured and this can lead to arrays with higher connectivity than those observed in the discrete pyridylimine architectures.     

Increased dimensionalities of zinc-diphenic acid coordination polymers by simultaneous or subsequent addition of neutral bridging ligands

Three coordination polymers containing zinc and diphenic acid (H2dpa) were synthesised by solvothermal reaction. Zn(dpa)(H2O) is a one-dimensional coordination polymer that consists of parallel ladder-like chains. One carboxylate group of the diphenic acid coordinates two zinc atoms forming a dinuclear unit which composes the steps of the ladder. The other carboxylate connects to a zinc atom in the next step of the ladder. The fourth coordination site at the zinc atom is occupied by water. Attempts to crosslink the chains by replacing the water molecule with the neutral ligands triethylenediamine (dabco) or 4,4'-bipyridyl lead to the compounds Zn2(dpa)2(dabco) and Zn(dpa)(4,4'-bpy). Their structures can be rationalised as being derived from action of the neutral ligand on Zn(dpa)(H2O), and while they are most conveniently prepared in a one-pot synthesis, it is also possible to obtain them by exposing Zn(dpa)(H2O) to the respective neutral ligand. Zn2(dpa)2(dabco) is a layered two-dimensional coordination polymer in which dinculear zinc carboxylate paddle wheel units and the dabco ligand form infinite linear chains. The chains are interconnected by the dpa unit. The structure of Zn(dpa)(4,4'-bpy) consists of two identical interpenetrating three-dimensional networks. In the network, helical Zn(dpa) chains are interconnected by the rigid 4,4'-bipyridine ligand. Thermogravimetric analysis indicates a high thermal stability of this coordination polymer with decomposition occurring in the range 350-450 degrees C. This is complemented by X-ray thermodiffractometry that indicates a phase transition at 337 degrees C and the final loss of crystallinity at 427 degrees C. The room temperature phase expands drastically along one axis and contracts along the other two axes on heating.     

Novel coordination polymers based on the tetrathioterephthalate dianion as the bridging ligand

The first examples of coordination polymers based on the tetrathioterephthalate dianion as the bridging ligand are reported. Two novel compounds, [M(S(2)CC(6)H(4)CS(2))(DMF)(2)](DMF) (M = Zn, Mn; DMF = dimethylformamide), have been synthesized, and their structural and optical properties were investigated.     

Magnetic study on a two-dimensional coordination polymer with mixed bridging ligands

A two-dimensional coordination polymer, [Co(mu(1,3)-SCN)(2)(mu(1,6)-dmpzdo)](n)() (where dmpzdo = 2,5-dimethylpyrazine-1,4-dioxide), has been synthesized and its crystal structure determined by X-ray crystallography. In the complex, the adjacent Co(II) ions are coordinated by mu(1,3)-SCN(-) bridging ligands which forms a one-dimensional chain along the a axis; the one-dimensional chains are further connected by mu(1,6)-dmpzdo bridging ligands which leads to the formation of a two-dimensional layer on the ac plane. The theoretical calculations reveal that a ferromagnetic coupling exists between the mu(1,3)-SCN(-) bridging Co(II) ions and an anti-ferromagnetic interaction between the mu(1,6)-dmpzdo bridging Co(II) ions, and the anti-ferromagnetic interaction is stronger than the ferromagnetic interaction. The fitting of the variable-temperature (34-300 K) magnetic susceptibilities reveals that there is an anti-ferromagnetic coupling between the bridging Co(II) ions with the magnetic coupling constant J = -3.52 cm(-1).     

Metal complexes of bridging neutral radical ligands: pymDTDA and pymDSDA

Metal complexes of the 4-(2'-pyrimidyl)-1,2,3,5-dithiadiazolyl (pymDTDA) neutral radical ligand and its selenium analogue (pymDSDA) are presented. The following series of metal ions has been studied using M(hfac)(2) as the coordination fragment of choice (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato): Mn(II), Co(II), Ni(II), and Zn(II). The binuclear cobalt and nickel complexes of pymDTDA both exhibit ferromagnetic (FM) coupling between the unpaired electrons on the ligand and the metal ion, while the binuclear zinc complex of pymDTDA is presented as a comparative example incorporating a diamagnetic metal ion. The binuclear manganese complex of pymDTDA, reported in a preliminary communication, is compared to the pymDSDA analogue, and new insight into the magnetic behavior reveals that intermolecular magnetic coupling, mediated by chalcogen-oxygen contacts, gives rise to a significant increase in the χT product at low temperature. Surprisingly, the binuclear nickel complex of pymDSDA forms dimers in the solid state, as do the mononuclear complexes of cobalt and nickel with pymDTDA. In addition, mixed mononuclear/binuclear complexes of Mn- and Zn(pymDTDA) have been identified.     

Porous coordination polymers based on three planar rigid ligands

During the last two decades,porous coordination polymers(PCPs),usually called as metal-organic frameworks(MOFs),have been developed rapidly due to their versatile structural diversities and potential physical and chemical functions.This article provides a short review of recent advances in the design and constructions of porous coordination polymers based on three planar rigid ligands,including imidazole-4,5-dicarboxlate(H3IDC),1H-tetrazole(HTz),as well as 1H-tetrazole-5-carboxylate(H2Tzc).Their preparation...     

Distinct structures of coordination polymers incorporating flexible triazole-based ligand: topological diversities, crystal structures and property studies

Six new coordination polymers, namely {[Zn(btec)(0.5)(btmb)]·2H(2)O}(n) (1), {[Co(btec)(0.5)(btmb)(H(2)O)]·3H(2)O}(n) (2), {[Cu(btec)(0.5)(btmb)]·H(2)O}(n) (3), {[Cu(4)(btc)(4)(btmb)(4)]·H(2)O}(n) (4), {[Co(3)(bta)(2)(btmb)(2)]·2H(2)O}(n) (5), [Co(Hbta)(btmb)](n) (6) (H(4)btec = 1,2,4,5-benzenetetracarboxylate, H(3)btc = 1,3,5-benzenetricarboxylate, H(3)bta = 1,2,4-benzenetricarboxylate and btmb = 4,4'-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been successfully synthesized under hydrothermal conditions. All these complexes were structurally determined by single-crystal X-ray diffraction, elemental analysis, IR, TGA and XRD. Crystal structural analysis reveals that 1 is the first example of an unusual 3D framework with (8(6)) topology containing a 2D molecular fabric structure. Complex 2 exhibits a 3D NbO network with (6(4)·8(2)) topology. In 3, Cu(II) ions are coordinated by anti-conformational btmb ligands to form left- and right-handed double helices, which are further bridged by the 4-connected btec(4-) anions to give a 3D porous network. Complex 4 presents a rare 3D gra network structure with (6(3))(6(9)·8) topology. 5 and 6 were obtained through controllable pH values of solution, 5 features a scarce binodal (3,8)-connected tfz-d framework with the trinuclear Co(II) clusters acting as nodes, whereas 6 has an extended 2D 4(4) grid-like layer and the adjacent 2D layers are interconnected by strong hydrogen bonding interactions into a 3D supramolecular framework. The structural diversities indicate that distinct organic acid ligands, the nature of metal ions and the pH value play crucial roles in modulating the formation of the resulting coordination complexes and the connectivity of the ultimate topological nets. Moreover, magnetic susceptibility measurement of 5 indicates the presence of weak ferromagnetic interactions between the Co(II) ions bridged by carboxylate groups.     

Construction of novel coordination polymers with simple ligands

Three different types of metal-organic polymers have been prepared by a solution diffusion process carried out at room temperature. Crystals of the copper coordination polymers [CuX(4,4′-bipy)] _n (X = Cl, Br, I) have been obtained by the reaction of 4,4′-bipyridine ligands with Cu₂X₂ fragments to yield a three-dimensional network consisting of four interlocking planar lattices. Single crystals of [Cu₂(1,2,4,5-BTC)(DMF)₂] _n (1,2,4,5-BTC = 1,2,4,5-benzene tetracarboxylate) have been grown by slow diffusion from solutions of a mixture of CuBr₂, 2,2′-dithiosalicylic acid, and sodium azide plus a mixture of 1,2,4,5-H₄BTC and 4-cyanopyridine. The complex [Co(1,3,5-BTC)(4,4′-bipy)] _n (1,3,5-BTC = 1,3,5-benzene tricarboxylate) has a 3D open framework structure involving terminal cobalt atoms plus bridging 1,3,5-BTC and 4,4′-bipyridine ligands.     

Effect of bis-triazole based secondary ligands on the structure of coordination polymers generated from terephthalic acid

Reactions of Zn/Cd(ClO₄)₂·6H₂O and terephthalic acid (H₂BDC) with three bis-triazole ligands afforded three coordination polymers under solvothermal conditions, {[Zn(BDC)(L1)]·H₂BDC}_n (1), {[Zn(BDC)(L2)_0.5]·H₂O}_n (2), and {[Cd₂(BDC)₂(L3)(DMF)(H₂O)₂]·2H₂O]}_n (3) (L1 = bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane, L2 = bis(4-(4H-1,2,4-triazol-4-yl)phenyl)ethane, and L3 = 1,4-bis(4H-1,2,4-triazol-4-yl)benzene). Solid 1 displayed a 2-D structure which contained two kinds of rings. Both 2 and 3 were 3-D threefold interpenetrating frameworks. Solid 2 showed a α–Po-related net, while 3 exhibited an acs-related network with a binuclear node. Furthermore, the photoluminescent properties of 1–3 were investigated.     

Formation of five-connected three-dimensional coordination polymers through the bridging function of the anions

New coordination polymers based on 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (L) with the composition [M₂(L)₄A(NCS)₂] (M²⁺ = Co²⁺, Zn²⁺, Cd²⁺; A^2? = SiF ₆ ^2? , SeO ₄ ^2? ) have been synthesized and characterized by IR spectroscopy and X-ray diffraction. According to X-ray diffraction data, cobalt compounds crystallize in the orthorhombic system with the following unit cell parameters, [Co₂(L)₄SiF₆(NCS)₂] · 3CHCl₃ · CH₃OH: a = 20.568(4), b = 14.568(3), c = 22.929(5) Å, α = β = γ = 90°, V = 6870(2) ų, space group Pbca (no. 61), R(I > 2σ(I)) = 0.0514; [Co₂(L)₄SeO₄(NCS)₂] · 2CHCl₃ · 2CH₃OH · H₂O: a = 13.721(2), b = 21.539(3), c = 22.417(3) Å, α = β = γ = 90°, V = 6625(2) ų, space group P2₁2₁2₁ (no. 19), R(I > 2σ(I)) = 0.0452. The 3D structure of the coordination polymers is composed of wavelike two-dimensional coordination layers [ML₂]_n connected by bridging anions SiF ₆ ^2? , or Se O ₄ ^2? . The complexes have the same five-bonded topology but different symmetry.     

A discrete dimer of coordination clusters connected through additional bridging ligands

The combination of directionality and unsaturated metal sites in bowl-shaped coordination clusters [Ag(4)L(3)(SbF(6))](3+){L = 2,4,6-tris(diphenylphosphino)triazine} results in the formation of discrete dimers on reaction with additional bridging ligands.     

Mixed-valence copper coordination polymers based on CuSCN or CuN3 as bridging motifs

Two novel mixed valence copper coordination polymers, [Cu(2-pac)₂(CuN₃)(H₂O)] _n (1) and [Cu(2-pac)₂(CuSCN)₂] _n (2), have been prepared through hydrothermal synthesis and analyzed for structure determination, which exhibit two- and three-dimensional structures respectively. In complex (1), zigzag chains of [CuN₃] _n running parallel to thec direction are interconnected by Cu(2pac)₂ to form a two-dimensional layer structure. In complex (2), the arrangement of μ-1,1,3 bridging thiocyanate ligand leads to the formation of ten-membered Cu—SCN— Cu—S—Cu—NCS rings, and each Cu atom is further linked by Cu(2-pac)₂ to afford a three-dimensional configuration.

     

Lanthanide-transition metal coordination polymers based on multiple N- and O-donor ligands

Lanthanide-transition metal (Ln-M) coordination polymers have attracted extensive interest because they exhibit novel physical properties originating from the interactions between distinct metal ions. This review mainly describes our recent work in the design of Ln-M coordination polymers through the assembly of different metal ions and organic ligands, especially the ligands with multiple N- and O-donor atoms. Many of these crystalline Ln-M materials exhibit intriguing structural motifs and interesting magnetic properties.     

Mixed-valence copper coordination polymers based on CuSCN or CuN_3 as bridging motifs

Two novel mixed valence copper coordination polymers, [Cu(2-pac)2(CuN3)(H2O)]n (1) and [Cu(2-pac)2(CuSCN)2]n (2), have been prepared through hydrothermal synthesis and analyzed for structure determination, which exhibit two and three-dimensional structures respectively. In complex (1), zigzag chains of [CuN3]n running parallel to the c direction are interconnected by Cu(2pac)2 to form a two-dimensional layer structure. In complex (2), the arrangement ofμ-1,1,3 bridging thiocyanate ligand leads to the formation of ten-membered Cu-SCN-Cu-S-Cu-NCS rings, and each Cu atom is further linked by Cu(2-pac)2 to afford a three-dimensional configuration.     

Four silver-containing coordination polymers based on bis(imidazole) ligands

Four coordination polymers, [Ag(L¹)](m-Hbdc) (1), [Ag(L¹)]₂(p-bdc)?·?8H₂O (2), [Ag(Hbtc)(L¹)][Ag(L¹)]?·?2H₂O (3) and [Ag₂(L²)₂](OH-bdc)₂?·?4H₂O (4), where L¹?=?1,1′-(1,4-butanediyl)bis(imidazole), L²?=?1,2-bis(imidazol-1-ylmethyl)benzene, m-H₂bdc?=?1,3-benzenedicarboxylic acid, p-H₂bdc?=?1,4-benzenedicarboxylic acid, H₃btc?=?1,3,5-benzenetricarboxylic acid, and OH–H₂bdc?=?5-hydroxisophthalic acid, were synthesized under hydrothermal conditions. Compound 1 contains a–Ag-L¹–Ag-L¹–chain and a hydrogen-bonding interaction induced–(m-Hbdc)-(m-Hbdc)–chain. Compound 2 consists of two independent–Ag-L¹–Ag-L¹–chains. P-bdc anions are not coordinated. Hydrogen bonds form a 3D supramolecular structure. A novel (H₂O)₁₆ cluster is formed by lattice water molecules in 2. Compound 3 contains a–Ag-L¹–Ag-L¹–and a–Ag(Hbtc)-L¹–Ag(Hbtc)-L¹–chain. The packing diagram shows a 2D criss-cross supramolecular structure, with?π?···?π?and C–H ···?π?interactions stabilizing the framework. Compound 4 contains a [Ag₂(L²)₂]²⁺ dimer with hydrogen-bonding,?π?··· π, and Ag ··· O interactions forming a 3D supramolecular framework. The luminescent properties for these compounds in the solid state are discussed.