Novel 3D, 2D, and 0D first-row coordination compounds with 4,4'-bipyridine-N,N'-dioxide incorporating sulfur-containing anions

The reaction of M(S2O6) (M = Cu(II), Ni(II), and Co(II)) with 4,4'-bipyridine-N,N'-dioxide (bpdo) results in the formation of novel 3D, 2D, and mononuclear complexes. Complex 1, {[Cu(H2O)(bpdo)2](S2O6)(H2O)}n, is a 2-D wavelike polymer with the Cu(II) ion located on a 2-fold axis and having a distorted square-pyramidal coordination sphere. With Co(II) and Ni(II), 3-D complexes, {[M(bpdo)3](S2O6)(C2H5OH)7}n [M = Co(II) (2), Ni(II) (3)], were obtained. The metal atoms are situated on centers of symmetry and have octahedral environments coordinated to six bpdo molecules. The same reaction in aqueous solution with a metal/ligand ratio of 1:1 results in the formation of mononuclear complexes, {[M(bpdo)(H2O)5](SO4)(H2O)2} [M = Co(II) (4), Ni(II) (5)], accompanied by the decomposition of the dithionate anions S2O6(2-) to sulfate anions SO4(2-).     

镍螺旋化合物及其杂银配位聚合物的设计合成与结构

采用两个易扭转异构的双三齿有机配体，双吡啶二甲基-6,6′-二酰肼-2,2′-连吡啶(H₂L¹)和双吡啶二乙基-6,6′-二酰肼-2,2′-连吡啶(H₂L²)，和金属镍离子组装得到2个金属螺旋体(helicate)，Ni₂(HL¹)₂(PF₆)(BF₄)(CH₃OH)(H₂O)₂ (1)和Ni₂(HL²)(H₂L²)(ClO₄)₃(C₂H₅OH)(CH₃OH)H₂O)₃ (2),并测定了它们的晶体结构。同时由配体H₂L³出发,通过逐级组装的方法,得到一个镍-银杂金属的配位聚合物Ni₂Ag₂(HL³)₂(ClO₄)₂(CH₃CN)₃ (3)。单晶结构表明，配位聚合物3中配体H₂L³首先与镍离子组装成分子盒化合物(molecular box)，该结构单元进一步通过Ag离子与分子盒外围N原子配位，使分子盒互相串连成一维配位聚合物3，分子盒聚集体沿c方向伸展成一维链结构，链与链之间相互平行，进一步堆积成二维孔道结构。     

Reinvestigation of the M(II) (M = Ni, Co)/tetrathiafulvalenetetracarboxylate system using high-throughput methods: isolation of a molecular complex and its single-crystal-to-single-crystal transformation to a two-dimensional coordination polymer

A high-throughput methodology combined with X-ray powder diffraction measurements was used to investigate the reactivity of the TetraThiaFulvalene TetraCarboxylic acid ((TTF-TC)H(4)) with divalent metals (M = Ni, Co) under various reaction conditions (stoichiometry, pH, temperature). Two new crystalline phases were identified and then studied by single crystal X-ray diffraction. Whereas the first one appears to be a simple salt, the second one, formulated {[M(H(2)O)(4)](2)(TTF-TC)}·4H(2)O, is built of 2:1 M:TTF-TC molecular complexes and labeled MIL-136(Ni, Co) (MIL stands for Materials Institute Lavoisier). The combination of thermogravimetric analysis and thermodiffraction studies reveals that MIL-136(Ni) exhibits a complex dehydration behavior. Indeed, a partial dehydration/rehydration process led to the single-crystal-to-single-crystal transformation of the molecular compound in a two-dimensional coordination polymer formulated {[Ni(2)(H(2)O)(5)(TTF-TC)]}·H(2)O (MIL-136'(Ni)). Magnetic and redox properties of MIL-136(Ni, Co) were investigated. Magnetic measurements indicate that all the magnetic coupling, intra- and intermolecular, are very weak; thus, the magnetic data of MIL-136(Ni, Co) have been interpreted in term of single-ion spin orbit coupling. Solid state cyclic voltammetry of MIL-136(Ni, Co) presents three reversible waves which were assigned to the redox activity of the TTF core and the metallic cations. In contrast to solids based on TTF linkers and alkaline ions, the MIL-136(Ni, Co) complexes do not act as excellent positive electrode materials for Li batteries, but present two reversible electron oxidation of the TTF core. These observations were tentatively related to the strength of the metal-carboxylate bond.     

Effects of protonation and metal coordination on intramolecular charge transfer of tetrathiafulvalene compound

A protonated bifunctional pyridine-based tetrathiafulvalene (TTF) derivative (DMT-TTF-pyH)NO3 and a copper(II) complex Cu(acac)2(DMT-TTF-py)2 have been obtained and studied. Electronic spectra of the protonated compound show a large ICT (intramolecular charge transfer) band shift (Deltalambda=136 nm) compared with that of the neutral compound. Cyclic voltammetry also shows a large shift of the redox potentials (DeltaE1/2(1)=77 mV). Theoretical calculation suggests that the pyridium substituent is a strong pi-electron acceptor. Crystal structures of the protonated compound and the metal complex have been obtained. The dihedral angle between least-squares planes of the pyridyl group and the dithiole ring might reflect the intensity of the ICT effect between the TTF moiety and the pyridyl group. It is also noteworthy that the TTF moiety could be oxidized to TTF2+ dication by Fe(ClO4)(3).6H2O when forming a metal complex, while the protonated TTF derivative can only be oxidized to the TTF*+ radical cation by Fe(ClO4)(3).6H2O even with an excess amount of the Fe(III) salt, which can be used to control the oxidation process to obtain neutral TTF, TTF*+ radical cation, or TTF2+ dication.     

Single-strand helical complexes constructed from 2-pyridinyl-3-pyridinylmethanone: tuning the helical pitch length by variation of metal cation and/or counter anion

The new ligand 2-pyridinyl-3-pyridinylmethanone (L) proves to be an excellent building block for the construction of single-strand helical architectures. A series of helical complexes have been synthesized by the reaction of L with various metal salts, in which L exhibits three kinds of coordination modes involving two kinds of bridging conformations, resulting in four types of single-strand helical chains. The counter anions in the series of 2(1) helical silver(I) complexes {[Ag(L)]X}(infinity)(X = NO(3), 1; PF(6), 2; BF(4), 3; ClO(4), 4; CF(3)CO(2), 5; CF(3)SO(3), 6) are fully or partially embedded inside the cylindrical helix, and the pitch length corresponds not only to the size of the anion but also to its manner of docking into the groove of the helix. Formation of the helical structure in {[Cu(L)(CH(3)CN)(H(2)O)(ClO(4))]ClO(4)}(infinity)(7) is driven by Ow-H...O (perchlorate) hydrogen bonding that leads to a stable triangular motif which rigidly fixes the configuration of the helix. In {[Co(L)(H(2)O)(3)](ClO(4))(2).2H(2)O}(infinity)(8) and {[Zn(L)(H(2)O)(3)](CF(3)SO(3))(2).H(2)O}(infinity)(9), similar helical chains without anion embedment suggest that the pitch length can be tuned by the size of metal cations. Notably, complex {[Ag(L)]CF(3)SO(3)}(infinity)(10), a conformational polymorph of , has a 4(1) helix induced by argentophilic interaction.     

Solvent control: dinuclear versus tetranuclear complexes of a bis-tetradentate pyrimidine-based ligand

A new bis-tetradentate acyclic amine ligand L(Et) has been synthesized from 4,6-bis(aminomethyl)-2-phenylpyrimidine and 2-vinylpyridine. Dinuclear complexes, Mn(II)(2)L(Et)(MeCN)(H(2)O)(3)(ClO(4))(4) (1), Fe(II)(2)L(Et)(H(2)O)(4)(BF(4))(4) (2), Co(II)(2)L(Et)(H(2)O)(3)(MeCN)(2)(BF(4))(4) (3), Ni(II)(2)L(Et)(H(2)O)(4)(BF(4))(4) (4), Ni(II)(2)L(Et)(H(2)O)(4)(ClO(4))(4)·8H(2)O (4'), Cu(II)(2)L(Et)(BF(4))(4)·MeCN (5), Zn(II)(2)L(Et)(BF(4))(2)(BF(4))(2)·?MeCN (6), were obtained from 1 : 2 reactions of L(Et) and the appropriate metal salts in MeCN, whereas in MeOH tetranuclear complexes, Mn(II)(4)(L(Et))(2)(OH)(4)(ClO(4))(4) (7), Fe(II)(4)(L(Et))(2)(F)(4)(BF(4))(4)·5/2H(2)O (8), Co(II)(4)(L(Et))(2)(F)(4)(BF(4))(4)·3H(2)O (9), Ni(II)(4)(L(Et))(2)(F)(4)(BF(4))(4)·4H(2)O (10), Cu(II)(4)(L(Et))(2)(F)(4)(BF(4))(4)·3H(2)O (11) and Zn(II)(4)(L(Et))(2)(F)(4)(BF(4))(4) (12), result. Six complexes have been structurally characterized: in all cases each L(Et) is bis-tetradentate and provides a pyrimidine bridge between two metal centres. As originally anticipated, complexes 1, 4' and 6 are dinuclear, while 9, 10 and 12 are revealed to be tetranuclear, with two M(2)(L(Et))(4+) moieties bridged by two pairs of fluoride anions. Weak to moderate antiferromagnetic coupling between the metal centres is a feature of complexes 2, 3, 4, 8, 9 and 10. The dinuclear complexes 1-6 undergo multiple, mostly irreversible, redox processes. However, the pyrimidine-based dicopper(II) complex 5 undergoes a two electron quasi-reversible reduction, Cu(II)(2)→ Cu(I)(2), and this occurs at a more positive potential [E(m) = +0.11 V (E(pc) = -0.03 and E(pa) = +0.26 V) vs. 0.01 M AgNO(3)/Ag] than for either of the dicopper(II) complexes of the analogous pyrazine-based ligands.     

Metal-carboxylate coordination polymers with redox-active moiety of tetrathiafulvalene (TTF)

Though numerous metal-organic frameworks or polymers have been reported, the organic building blocks are usually not redox-active. On the other hand, some mono-, di- or tri-nuclear compounds with tetrathiafulvalene (TTF) have been prepared, although little is known about the coordination polymers combined with paramagnetic metals and organic TTF ligands. We report herein a series of coordination polymers of copper(II) and manganese(II) with TTF dicarboxylate ligand (L). Compound 1, [CuL(2,2-bpy)](n), is a one-dimensional (1-D) coordination polymer with five-coordinated square-pyramidal Cu(II) centers. Mn(II) complex 2, [MnL(2,2-bpy)](n), also takes a 1-D structure, showing a double-bridged mode by carboxylate groups. The 4,4-bipyridine compound 3, [MnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, takes a 2-D grid network. A zinc(II) compound 4, [ZnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, isomorphous structure with 3, is also presented. The electrochemical properties of the solid-state compounds were investigated by cyclic voltammetry using surface-modified electrodes. As usually observed in TTF derivatives, two sets of redox-waves were observed. The values of E(1/2)(1) of compounds 1-4 are in the order of 2(Mn) ≈ 3(Mn) < 1(Cu) < 4(Zn), indicating that the metal coordination can affect the potential shift of the TTF ligand. Weak antiferromagnetic exchanges are observed for compounds 1, 2, and 3.     

Inorganic-organic hybrid compounds based on octamolybdates and metal-organic fragments with flexible multidentate ligand: syntheses, structures and characterization

Six polyoxometalate-based (POM) hybrid materials based on octamolybdate building blocks and metal-organic fragments with flexible multidentate ligand, namely [Cu(II)(2)(ttb)(2)(β-Mo(8)O(26))(H(2)O)(2)]·2H(2)O (1), Cu(I)(4)(ttb)(2)(β-Mo(8)O(26))(H(2)O) (2), [Cu(I)(4)(ttb)(3)(β-Mo(8)O(26))] (3), [Ni(2)(ttb)(2)(β-Mo(8)O(26))(H(2)O)(6)]·2H(2)O (4), [Zn(2)(ttb)(2)(α-Mo(8)O(26))(H(2)O)(2)] (5), and [Ag(4)(ttb)(2)(β-Mo(8)O(26))] (6), where ttb = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethyl benzene, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, TGA, IR spectra, and electrochemistry. Compounds 1 and 2 exhibit three-dimensional (3D) 2-fold interpenetrating frameworks with (3,6)-connected (4(1)·6(2))(4(2)·6(10)·10(3)) and (3,4)-connected (6(2)·8(1))(2)(6(2)·8(4)) topologies, respectively. We are not aware of any other examples of interpenetrating (3,6)- and (3,4)-connected frameworks which involves the octamolybdates. Compound 3 shows a rare two-dimensional (2D) 2-fold interpenetrating network structure. In compound 4, a 3D supramolecular framework with the channels is constructed by the hydrogen-bonding interactions between (β-Mo(8)O(26))(4-) polyanions and the Ni-ttb double layers, in which the guest (β-Mo(8)O(26))(4-) anions are included. If ZnO interactions are considered, the structure of 5 is a 3D (3,4)-connected framework with (4·8(2))(4·8(2)·10(3)) topology. In 6, the ttb ligand as a tetradentate ligand links the Ag atoms to yield a 2D POM-based network. By careful inspection of the structures of 1-6, it can be seen that the ttb ligand, the metal ion and the coordination mode of the octamolybdate anion play important roles in the formation of the POM-based MOFs.     

Syntheses and characterization of six coordination polymers of zinc(II) and cobalt(II) with 1,3,5-benzenetricarboxylate anion and bis(imidazole) ligands

Six new coordination polymers, namely [Zn1.5(BTC)(L1)(H2O)2].1.5H2O (1), [Zn3(BTC)2(L2)3] (2), [Zn3(BTC)2(L3)1.5(H2O)].H2O (3), [Co6(BTC)4(L1)6(H2O)3].9H2O (4), [Co1.5(BTC)(L2)1.5].0.25H2O (5), and [Co4(BTC)2(L3)2(OH)2(H2O)].4.5H2O (6), where L1 = 1,2-bis(imidazol-1-ylmethyl)benzene, L2 = 1,3-bis(imidazol-1-ylmethyl)benzene, L3 = 1,1'-(1,4-butanediyl)bis(imidazole), and BTC = 1,3,5-benzenetricarboxylate anion, were synthesized under hydrothermal conditions. In 1-6, each of L1-L3 serves as a bidentate bridging ligand. In 1, BTC anions act as tridentate ligands, and compound 1 shows a 2D polymeric structure which consists of 2-fold interpenetrating (6, 3) networks. In compound 2, BTC anions coordinate to zinc cations as tridentate ligands to form a net with (64.82)2(86)(62.8)2 topology. In compound 3, BTC anions act as tetradentate ligands and coordinate to zinc cations to form a net with (4.62.83)2(8.102)(4.6.83.10)2 topology. In compound 5, each BTC anion coordinates to three Co cations, and the framework of 5 can be simplified as (64.82)2(62.82.102)(63)2 topology. For 4 and 6, the 2D cobalt-BTC layers are linked by bis(imidazole) ligands to form 3D frameworks. In 6, the Co centers are connected by micro3-OH and carboxylate O atoms to form two kinds of cobalt-oxygen clusters. Thermogravimetric analyses (TGA) for these compounds are discussed. The luminescent properties for 1-3 and magnetic properties for 4-6 are also discussed in detail.     

A study of the complexation and extraction of Cu(II) sulfate and Ni(II) sulfate by N3O2-donor macrocycles

Comparative solvent extraction (water/chloroform) studies of Ni(II) and Cu(II) employing a dinonyl-substituted N3O2-donor macrocycle (L2) as extractant have been undertaken from sulfate, chloride, nitrate and acetate-containing aqueous media. Contrary to expectations, efficient extraction of both metal sulfates was observed, the degree of extraction being comparable (or slightly enhanced) relative to that observed for each of the other anionic systems. X-Ray diffraction studies of [NiL1(H2O)3]SO4 x 4H2O and [CuL1(H2O)]SO4 x 6.67 H2O (where L1 is the unsubstituted derivative of L2) show that each complex occurs as a hydrogen-bonded 'cluster', with the sulfate anions involved in hydrogen bonded networks that incorporate ligand amine protons and water molecules; in the copper complex, which adopts a dimeric arrangement, simultaneous sulfate binding to a copper site is also present. In each complex the macrocyclic ligand fails to coordinate via its ether oxygen donors but instead is arranged so that the metal ion and sulfate anions are somewhat shielded hydrophobically from the exterior of the complex cluster assembly.     

Indium sulfide clusters integrated with 2,2'-bipyridine complexes

Supertetrahedral compounds of chalcogenometalates (T3 cluster compounds) integrated with Ni-bpy (bpy = 2,2'-bipyridine) complex were prepared by a solvothermal technique. The compound [Ni(bpy)(3)](3)[H(4)In(10)S(20)]·bpy·2EG·6H(2)O (Mb-InS-1) (EG = ethylene glycol) consists of discrete T3 clusters of [H(4)In(10)S(20)](6-) with three [Ni(bpy)(3)](2+) cations. The compound [Ni(bpy)(3)](2)[H(2)In(10)S(19)]·bpy·2HEA·2H(2)O (Mb-InS-2) (EA = ethanolamine) is a 1-D polymer, in which zigzag T3 cluster chains are charge balanced by metal-bpy complex cations. The compound [Ni(bpy)(3)](7)[H(4)In(40)S(74)]·7Hbpy·3HEA·8H(2)O (Mb-InS-3) is a 2-D T3 polymer with cation layers of [Ni(bpy)(3)](2+). Integrating M-bpy complex cations into chalcogenido structures has been made with the aim of improving the photoabsorption of the materials. The electronic spectra showed the new bands of cation-anion charge-transfer (CACT) that is mainly caused by the S···H-C(py) contacts between the InS T3 supertetrahedral clusters and the [Ni(bpy)(3)](2+) cations.     

3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules. A pair of Cu(SO(3))(4)(7-) anions each act as a tridentate ligand towards a single Mn(II) centre when Mn(II) ions are combined with an excess of Cu(SO(3))(4)(7-). An anionic pentanuclear complex of composition {[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)} is formed when Fe(II) is added to a Cu(+)/SO(3)(2-) solution. Hydrated ferrous [Fe(H(2)O)(6)(2+)] and sodium ions act as counterions for the complexes and are responsible for the formation of an extensive hydrogen bond network within the crystal. Magnetic susceptibility studies over the temperature range 2-300 K show that weak ferromagnetic coupling occurs within the Cu(II) containing chains of Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O, while zero coupling exists in the pentanuclear cluster {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(NO(3))·H(2)O. Weak Mn(II)-O-S-O-Mn(II) antiferromagnetic coupling occurs in Na(H(2)O)(6){[Cu(I)(SO(3))(4)][Mn(II)(H(2)O)(2)](3)}, the latter formed when Mn was in excess during synthesis. The compound, Na(3)(H(2)O)(6)[Fe(II)(H(2)O)(6)](2){[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)}·H(2)O, contained trace magnetic impurities that affected the expected magnetic behaviour.     

Coordination chemistry of a pi-extended, rigid and redox-active tetrathiafulvalene-fused Schiff-base ligand

A pi-extended, redox-active tetradentate tetrathiafulvalene-fused salphen [salphen = N,N'-phenylenebis(salicylideneimine)] compound (L) was prepared via a direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde. Its chelating coordination ability has been demonstrated by the formation of the corresponding transition metal complexes in the presence of M(OAc)2.nH2O (M = Co(II), Ni(II), Cu(II)) and FeCl3.6H2O. Three complexes have been characterized by single-crystal X-ray diffraction analysis showing that the TTF-salphen ligand coordinates to the metal ions in a planar mode through the nitrogen and oxygen atoms in a N2O2 cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III) complex is formed. These paramagnetic complexes are promising building blocks for the construction of dual functional materials due to their unique structural features (planarity and rigidity) as well as their inherent redox properties.     

Hydrothermal synthesis, structure, and luminescent properties of selected Zn(II)/Cd(II) coordination polymers constructed from 3,5-bis(x-pyridyl)-1,2,4-triazole (x = 3, 4)

Utilizing 3,5-bis(x-pyridyl)-1,2,4-triazole (x-Hpytz, x = 3; x = 4) as multidentate ligands, six novel coordination polymers with Zn(II) or Cd(II) metal ions were prepared: [Zn(3-pytz)(0.5)(OH)(0.5)Cl](n) (1, 1D ladder), {[Zn(3-Hpytz)(H(2)O)(4)] [Zn(3-Hpytz)(H(2)O)(3)·SO(4)]SO(4)·5H(2)O}(n) (2·5H(2)O, 1D chain), [Cd(3-Hpytz)(SO(4))](n) (3, 3D framework), {[Cd(3-Hyptz)SO(4)·3H(2)O]·2H(2)O}(n) (4·2H(2)O, 1D chain), [Zn(4-pytz)Cl](n) (5, 3D framework) and [Zn(2)(4-pytz)(SO(4))(OH)](n) (6, 3D framework). All compounds were obtained from hydrothermal reactions, with the exception of compound 4 which was obtained by solvent diffusion at room temperature. All compounds were characterized by FTIR, elemental analysis and TGA analysis and their structures were determined by X-ray diffraction. All compounds exhibited substantial thermal stability and showed photofluorescent properties that resulted from ligand π-π* transition.     

Structures, host-guest chemistry and mechanism of stepwise self-assembly of M4L6 tetrahedral cage complexes

The ligand L(bip), containing two bidentate pyrazolyl-pyridine termini separated by a 3,3'-biphenyl spacer, has been used to prepare tetrahedral cage complexes of the form [M(4)(L(bip))(6)]X(8), in which a bridging ligand spans each of the six edges of the M(4) tetrahedron. Several new examples have been structurally characterized with a variety of metal cation and different anions in order to examine interactions between the cationic cage and various anions. Small anions such as BF(4)(-) and NO(3)(-) can occupy the central cavity where they are anchored by an array of CH···F or CH···O hydrogen-bonding interactions with the interior surface of the cage, but larger anions such as naphthyl-1-sulfonate or tetraphenylborate lie outside the cavity and interact with the external surface of the cage via CH···π interactions or CH···O hydrogen bonds. The cages with M = Co and M = Cd have been examined in detail by NMR spectroscopy. For [Co(4)(L(bip))(6)](BF(4))(8) the (1)H NMR spectrum is paramagnetically shifted over the range -85 to +110 ppm, but the spectrum has been completely assigned by correlation of measured T(1) relaxation times of each peak with Co···H distances. (19)F DOSY measurements on the anions show that at low temperature a [BF(4)](-) anion diffuses at a similar rate to the cage superstructure surrounding it, indicating that it is trapped inside the central cage cavity. Furthermore, the equilibrium step-by-step self-assembly of the cage superstructure has been elucidated by detailed modeling of spectroscopic titrations at multiple temperatures of an acetonitrile solution of L(bip) into an acetonitrile solution of Co(BF(4))(2). Six species have been identified: [Co(2)L(bip)](4+), [Co(2)(L(bip))(2)](4+), [Co(4)(L(bip))(6)](8+), [Co(4)(L(bip))(8)](8+), [Co(2)(L(bip))(5)](4+), and [Co(L(bip))(3)](2+). Overall the assembly of the cage is entropy, and not enthalpy, driven. Once assembled, the cages show remarkable kinetic inertness due to their mechanically entangled nature: scrambling of metal cations between the sites of pure Co(4) and Cd(4) cages to give a statistical mixture of Co(4), Co(3)Cd, Co(2)Cd(2), CoCd(3) and Cd(4) cages takes months in solution at room temperature.     

Syntheses, structures and properties of silver-organic frameworks constructed with 1,2,3,4-benzenetetracarboxylic acid

The reactions of 1,2,3,4-benzenetetracarboxylic acid (H(4)mpda) and different silver(I) salts under hydrothermal or solvent evaporation conditions yielded four unusual coordination complexes with interesting frameworks: [Ag(4)(mpda)](n) (1), {[Ag(2.5)(mpda)(bpy)(2)]·[Ag(bpy)]·[Ag(bpy)(H(2)O)]·(NO(3))(0.5)·(H(2)O)(9)}(n) (2), {[Ag(5)(mpda)(2)(bpy)(4)]·[Ag(bpy)]·[Ag(bpy)(H(2)O)]·[Ag(bpy)(H(2)O)]·(H(2)O)(16)}(n) (3), {[Ag(2)(mpda)(H(2)O)]·[Ag(bpy)]·[Ag(bpy)]}(n) (4) (bpy = 4,4'-bipyridine). Complex 1 displays a novel (3,4,7)-connected {4.6(2)}{4.6(5)}{4(2).6(13).8(5).10} topology, in which the carboxylic groups of the mpda(4-) ligand adopt variable coordination modes. In 1, besides Ag-O coordination bonding, AgAg and Agaromatic intermolecular interactions also make their appearance. In complexes 2-4, rare architectures comprising three or four isolated coordination polymers within the same crystalline structure have been obtained, respectively. In 2 and 3, neighboring layers are linked together through water tapes into a three-dimensional supramolecular architecture, which is also consolidated by π···π stacking, while independent infinite rod-like polymer chains fill the void space between layers. Interestingly, an anionic (H(2)O-NO(3)(-))(n) layer, built from water tapes and nitrate anions as well as consolidated by the mpda(4-) ligands, has been structurally identified in compound 2. A new water tape constructed from alternating tetramers and decamers has been obtained in compound 3. In compound 4, a right-handed helical chain and two rod-like polymeric chains are interconnected through host-guest molecular recognition to generate a three-dimensional chiral supramolecular architecture. Bulk materials for 1 and 4 have second-harmonic generation activity, being approximately 0.6 and 0.4 times that of urea. The IR spectra, thermogravimetric analysis and luminescent properties of all compounds were also investigated.     

Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites-type double sulfates--an infrared spectroscopic study

Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl(2)(SO(4))(4)·22H(2)O, MnAl(2)(SO(4))(4)·22H(2)O and ZnAl(2)(SO(4))(4)·22H(2)O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase of the hydrogen bond strength of the bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified for each halotrichite-type compound. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that compounds with halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy.     

Catenation control in the two-dimensional coordination polymers based on tritopic carboxylate linkers and azamacrocyclic nickel(II) complexes

Four new coordination polymer frameworks, namely [(NiL(1))(3)(BTB)(2)]·6H(2)O, [(NiL(2))(3)(BTB)(2)]·6H(2)O, [(NiL(3))(3)(BTB)(2)]·6H(2)O and [(NiL(2))(3)(BTC)(2)]·10.25H(2)O (L(1) = 1,4,8,11-tetraazacyclotetradecane, L(2) = 3-methyl-1,3,5,8,12-pentaazacyclotetradecane, L(3) = 3,10-dimethyl-1,3,5,8,10,12-hexaazacyclotetradecane, BTC(3-) = benzene-1,3,5-tricarboxylate, BTB(3-) = 4,4',4'-benzene-1,3,5-triyl-tribenzoate) were prepared in water-N,N-dimethylformamide solutions. The molecular and crystal structures of these compounds are compared to the related coordination polymers formed by nickel(II) macrocyclic cations to examine the effect of carboxylate linker size on the framework architecture. Luminescent properties of the complexes based on the BTB(3-) bridging ligand are also discussed.     

Probing anion-pi interactions in 1-D Co(II), Ni(II), and Cd(II) coordination polymers containing flexible pyrazine ligands

Two flexible thioether-containing heterocyclic ligands bis(2-pyrazylmethyl)sulfide (L1) and 2-benzylsulfanylmethylpyrazine (L2) have arene rings with differing pi-acidities which were used to probe anion-pi binding in five 1-D coordination polymers formed from the metal salts Co(ClO4)2, Ni(NO3)2, and Cd(NO3)2. In {[Co(L1)(MeCN)2](ClO4)2}infinity (1), {[Ni(L1)(NO3)2]}infinity (2), and {[Cd2(L1)(MeCN)(H2O)(NO3)4].H2O}infinity (3.H2O), the symmetrical ligand L1 was bound facially to the metal center and was bridged through a pyrazine donor to an adjacent metal forming a polymer chain. The folding of L1 formed U-shaped pi-pockets in 1 and 3.H2O which encapsulated free and bound anions, respectively. The anions interacted with the pi-acidic centers in a variety of different binding modes including anion-pi-anion and pi-anion-pi sandwiching. A wider pi-pocket was formed in 2 which also contained anion-pi interactions. The polymer chains in 2 were interdigitated through a rare type of complementary T-shaped N(pyrazine)...pi interaction. In {[Co(L2)(H2O)3](ClO4)2.H2O}infinity (4.H2O) and {[Cd(L2)(H2O)(NO3)2]}infinity (5), the unsymmetrical ligand L2 chelated the metal center and bridged through a pyrazine donor to an adjacent metal forming a polymer chain. The ligand arrangement resulted in the anions in both structures being involved in only anion-pi-anion sandwich interactions. In 4.H2O, the noncoordinated ClO4- anions interacted with only one chain while in 5 the coordinated NO3- anions acted as anion-pi supramolecular synthons between chains. Comparison between the polymers formed with ligands L1 and L2 showed that only the more pi-acidic ring was involved in the anion-pi interactions.     

Anion binding by metallo-receptors of 5,5'-dicarbamate-2,2'-bipyridine ligands

Three 5,5'-dicarbamate-2,2'-bipyridine ligands (L = L(1)-L(3)) bearing ethyl, isopropyl or tert-butyl terminals, respectively, on the carbamate substituents were synthesized. Reaction of the ligands L with the transition metal ions M = Fe(2+), Cu(2+), Zn(2+) or Ru(2+) gave the complexes ML(n)X(2)·xG (1-12, n = 1-3; X = Cl, NO(3), ClO(4), BF(4), PF(6), ?SO(4); G = Et(2)O, DMSO, CH(3)OH, H(2)O), of which [Fe(L(2))(3)???SO(4)]·8.5H(2)O (2), [Fe(L(1))(3)???(BF(4))(2)]·2CH(3)OH (7), [Fe(L(2))(3)???(Et(2)O)(2)](BF(4))(2)·2CH(3)OH (8), [ZnCl(2)(L(1))][ZnCl(2)(L(1))(DMSO)]·2DMSO (9), [Zn(L(1))(3)???(NO(3))(2)]·2H(2)O (10), [Zn(L(2))(3)???(ClO(4))(Et(2)O)]ClO(4)·Et(2)O·2CH(3)OH·1.5H(2)O (11), and [Cu(L(1))(2)(DMSO)](ClO(4))(2)·2DMSO (12) were elucidated by single-crystal X-ray crystallography. In the complexes ML(n)X(2)·xG the metal ion is coordinated by n = 1, 2 or 3 chelating bipyridine moieties (with other anionic or solvent ligands for n = 1 and 2) depending on the transition metal and reaction conditions. Interestingly, the carbamate functionalities are involved in hydrogen bonding with various guests (anions or solvents), especially in the tris(chelate) complexes which feature the well-organized C(3)-clefts for effective guest inclusion. Moreover, the anion binding behavior of the pre-organized tris(chelate) complexes was investigated in solution by fluorescence titration using the emissive [RuL(3)](2+) moiety as a probe. The results show that fluorescent recognition of anion in solution can be achieved by the Ru(II) complexes which exhibit good selectivities for SO(4)(2-).