Synthesis, structure, and luminescent properties of microporous lanthanide metal-organic frameworks with inorganic rod-shaped building units

A series of microporous lanthanide metal-organic frameworks, Tb3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(H2O) (1) and Ln3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(C2H5OH)(0.5)(H2O)(0.5) [Ln = Dy (2), Ho (3), Er (4)], have been synthesized by the reaction of the lanthanide metal ion (Ln3+) with 1,4-benzenedicarboxylic acid and triethylenetetramine in a mixed solution of N,N'-dimethylformamide (DMF), water, and C(2)H(5)OH. X-ray diffraction analyses reveal that they are extremely similar in structure and crystallized in triclinic space group P. An edge-sharing metallic dimer and 4 metallic monomers assemble with 18 carboxylate groups to form discrete inorganic rod-shaped building units [Ln6(CO2)18], which link to each other through phenyl groups to lead to three-dimensional open frameworks with approximately 4 x 6 A rhombic channels along the [0,-1,1] direction. A water sorption isotherm proves that guest molecules in the framework of complex 1 can be removed to create permanent microporosity and about four water molecules per formula unit can be adsorbed into the micropores. These complexes exhibit blue fluorescence, and complex 1 shows a Tb3+ characteristic emission in the range of 450-650 nm.     

New functionalized flexible Al-MIL-53-X (X = -Cl, -Br, -CH3, -NO2, -(OH)2) solids: syntheses, characterization, sorption, and breathing behavior

Five new flexible functionalized aluminum hydroxo terephthalates [Al(OH)(BDC-X)]·n(guests) (BDC = 1,4-benzene-dicarboxylate; X = -Cl, 1-Cl; -Br, 2-Br; -CH(3), 3-CH(3); -NO(2), 4-NO(2); -(OH)(2), 5-OH(2)) were synthesized under solvothermal conditions. The as synthesized (Al-MIL-53-X-AS) as well as the activated compounds were characterized by X-ray powder diffraction (XRPD), IR spectroscopy, thermogravimetric (TG), and elemental analysis. Activation, that is, removal of unreacted H(2)BDC-X molecules and/or occluded solvent molecules, followed by hydration in air at room temperature, led to the narrow pore (NP) form of the title compounds [Al(OH)(BDC-X)]·n(H(2)O) (Al-MIL-53-X). Thermogravimetric analysis (TGA) and temperature-dependent XRPD (TDXRPD) experiments performed on the NP-form of the compounds indicate high thermal stability in the range 325-500 °C. As verified by N(2), CO(2), or H(2)O sorption measurements, most of the thermally activated compounds exhibit significant microporosity. Similar to pristine Al-MIL-53, the present compounds retain their structural flexibility depending on the nature of guest molecules and temperature, as verified by cell parameter determination from XRPD data. The breathing behavior of the functionalized frameworks upon dehydration-rehydration, investigated by temperature and time-dependent XRPD measurements, differs significantly compared to parent Al-MIL-53.     

Influence of ligand geometry on the formation of In-O chains in metal-oxide organic frameworks (MOOFs)

Three indium-oxide organic frameworks, In(2)O(1,3-BDC)(2), 1; In(OH)(2,6-NDC)(H(2)O), 2; and In(OH)(2,7-NDC)(H(2)O), 3 (BDC = benzene dicarboxylic acid and NDC = naphthalene dicarboxylic acid), were synthesized and characterized by thermogravimetric analysis, infrared spectroscopy, and single-crystal X-ray diffraction. Previously, we reported the structure of In(OH)(1,4-BDC).(0.75H(2)BDC), 0, where the framework is built by interconnecting In-OH-In chains with the BDC anions to form large diamond-shaped one-dimensional channels filled with guest molecules. Compounds 0-3 all contain In-O(H) chains, but the coordination and geometry depend on the nature of the dicarboxylate ligand. Compound 0 contains In-O octahedral centers that connect to form a single trans octahedral chain, while in compound 1, they connect to form a more complex double chain of octahedra. Both compounds 2 and 3 contain chains of connected pentagonal bipyramidal InO(6)(OH(2)) units. In 2, these units share trans vertices that are cross-linked by chelating 2,6-NDC anions, whereas in compound 3, cis vertices are shared to form chains that are linked by the 2,7-NDC anions.     

p-Xylene-selective metal-organic frameworks: a case of topology-directed selectivity

Para-disubstituted alkylaromatics such as p-xylene are preferentially adsorbed from an isomer mixture on three isostructural metal-organic frameworks: MIL-125(Ti) ([Ti(8)O(8)(OH)(4)(BDC)(6)]), MIL-125(Ti)-NH(2) ([Ti(8)O(8)(OH)(4)(BDC-NH(2))(6)]), and CAU-1(Al)-NH(2) ([Al(8)(OH)(4)(OCH(3))(8)(BDC-NH(2))(6)]) (BDC = 1,4-benzenedicarboxylate). Their unique structure contains octahedral cages, which can separate molecules on the basis of differences in packing and interaction with the pore walls, as well as smaller tetrahedral cages, which are capable of separating molecules by molecular sieving. These experimental data are in line with predictions by molecular simulations. Additional adsorption and microcalorimetric experiments provide insight in the complementary role of the two cage types in providing the para selectivity.     

Octahedral tilting in MM'X4 metal-oxide organic layer structures

Three metal-oxide organic frameworks have been synthesized and characterized: vanadium 1,4-benzenedicarboxylate, V2O2F0.6(OH)1.4(BDC).0.4H 2O (1); indium 1,4-benzenedicarboxylate, In 2F2.2(OH)1.8(BDC).1.6H2O (2); and aluminum 1,4-benzenedicarboxylate Al2F3(OH)(BDC) (3). The three-dimensional structures of 1, 2, and 3 have the same framework topology as the previously reported vanadium (III) 1,4-benzenedicarboxylate, VIII2(OH)2F2(BDC). The frameworks consist of inorganic layers constructed from corner sharing ML 6 octahedra (M=V, In, Al and L=OH, F) linked by BDC ligands. The structures are related to a general class of perovskite-related layer structures with composition MM'X4. The layers show characteristic distortions that can be related to tilting of the ML 6 octahedra. In particular the structure of 1 consists of O-V distances that strongly alternate along the b axis. The electronic consequences of this distortion then create a tilting of the 1,4-benzenedicarboxylate ligand about the a axis. Crystal data: 1, orthorhombic, space group Pmna, a=7.101(2) A, b=3.8416(11) A, c=20.570(6) A; 2, orthorhombic, space group Cmcm, a=7.490(4) A, b=21.803(1) A, c=8.154(4) A; 3, monoclinic, space group P2(1)/m, a=10.7569(8) A, b=6.7615(3) A, c=7.1291(3) A, beta=76.02(1) degrees.     

Dynamic and redox active pillared bilayer open framework: single-crystal-to-single-crystal transformations upon guest removal, guest exchange, and framework oxidation

A metal-organic pillared bilayer open framework having 3D channels, [Ni(2)(C(26)H(52)N(10))](3)[BTC](4).6C(5)H(5)N.36H(2)O (BOF-1, 1), has been assembled from bismacrocyclic nickel(II) complex [Ni(2)(C(26)H(52)N(10))(Cl)(4)].H(2)O and sodium 1,3,5-benzenetricarboxylate (Na(3)BTC). The channels are occupied by pyridine and water guest molecules. When the single crystal of 1 was dried in air and then heated at 75 degrees C for 1.5 h, respectively, [Ni(2)(C(26)H(52)N(10))](3)[BTC](4).30H(2)O (1') and [Ni(2)(C(26)H(52)N(10))](3)[BTC](4).4H(2)O (2) resulted with retention of the single crystallinity. The X-ray structures reveal spongelike dynamic behavior of the bilayer framework that reduces the interlayer distance in response to the amount of guest molecules. Solid 2 differentiates various alcohols. When 1 was immersed in pyridine and benzene, guest molecules were exchanged with retention of the single-crystal nature to give rise to [Ni(2)(C(26)H(52)N(10))](3)[BTC](4).20pyridine.6H(2)O (3) and [Ni(2)(C(26)H(52)N(10))](3)[BTC](4).14benzene.19H(2)O (4), respectively. Furthermore, crystal 1 reacted with I(2) via single-crystal-to-single-crystal transformation to produce [Ni(2)(C(26)H(52)N(10))](3)[C(9)H(3)O(6)](4)(I(3))(4).nI(2).17H(2)O (5) that consists of positively charged framework incorporating nickel(III) and nickel(II) ions and the channels including I(3)(-) and I(2).     

Two novel Dy8 and Dy11 clusters with cubane [Dy4(μ3-OH)4]8+ units exhibiting slow magnetic relaxation behaviour

Two unique octa- and hendeca-nuclear dysprosium(III) clusters incorporating [Dy(4)(μ(3)-OH)(4)](8+) cubane units have been synthesized with the 1,10-phenanthroline-2,9-dicarbaldehyde dioxime (H(2)phendox) ligand and DyCl(3)·6H(2)O or Dy(OAc)(3)·4H(2)O. They are [Dy(8)(OH)(8)(phendox)(6)(H(2)O)(8)]Cl(2)(OH)(2)·18H(2)O·18MeOH (1) and [Dy(11)(OH)(11)(phendox)(6)(phenda)(3)(OAc)(3)](OH)·40H(2)O·7MeOH (2). Adjacent Dy(8) in 1 or Dy(11) in 2 motifs are packed by off-set π-π interactions of the aromatic rings on phendox(2-) to generate a 3D supramolecular architecture in the honeycomb topology and with 1D or 3D channels along the c-axis. Adsorption research shows that complex 1 has selective adsorption ability for H(2)O over small gas molecules (H(2), N(2), CO(2)). Complex 2 is stable upon the removal of guest molecules and the desolvated compound absorbed a considerable amount of CO(2). Furthermore, the oximes underwent hydrolysis to carboxylic acid and the resulting 1,10-phenanthroline-2,9-dicarboxylate link the dysprosium atoms to form a hendecanuclear cluster of 2. Magnetic studies reveal that both clusters exhibit slow magnetic relaxation behavior, expanding upon the recent reports of the pure 4f type single-molecule magnets (SMMs).     

Unusual visible luminescence of aluminium polyoxocations in aqueous solution

Identification of aluminium polyoxocations, MO(4)Al(12)(OH)(24)(H(2)O)(12)(7/8+) (M = Al, Ga and Ge) (K-MAl(12)) and Al(30)O(8)(OH)(56)(H(2)O)(26)(18+) (Al(30)), by their luminescence is reported. The fluorescence behavior of K-Al(13) has been found to differ with different metal ions and anions, implying a new discovery of a potential ion sensor.     

Effect of alkyl substitueras in hydrophobic 8-quinolinol on the extraction of gallium(III) and applications to the separation of gallium(III) from aluminum(III)

The extraction of gallium(III) with newly prepared 5-alkyloxymethyl-8-quinolinol derivatives with alkyl substituent at the 2-position in 8-quinolinol moiety has been studied. The Ga(III)-5-octyloxymethyl-8-quinolinol (HO(8)Q), Ga(III)-2-methyl-5-octyloxymethyl-8-quinolinol (HMO(8)Q), Ga(III)-2-methyl-5-hexyloxymethyl-8-quinolinol (HM-O(6)Q), and Ga(HI)-2-n-butyl-5-hexyloxymethyl-8-quinolinol (HNBO(6)Q) complexes extracted in heptane from a perchloric acid medium were Ga(O(8)Q)(3), Ga(OH)(H(2)O)(MO(8)Q)(2), Ga(OH)(H(2)O)(MO(6)Q)(2) and Ga(OH)H(2)O)(NBO(6)Q)(2), respectively. The 2-tert-butyl-5-hexyloxymethyl-8-quinolinol did not exhibit any reactivity toward gallium(III). The extraction constants for Ga(O(8)Q)(3) (K(ex) = [Ga(O(8)Q)(3)](org) [H(+)](3)/[Ga(3+)][HO(8)Q](org)(3)), Ga(OH)(H(2)O)(MO(8)Q)(2) (K(ex) = [Ga(OH) (H(2)O)(MO(8)Q)(2)](org) [H(+)](3)/[Ga(3+)][HMO(8)Q](org)(2)), Ga(OH)(H(2)O)(2)(MO(6)Q)(2) and Ga(OH)(H(2)O)(NBO(6)Q)(2), which were extracted in heptane from an acidic solution, are 10(3.21 +/- 0.12), 10(-4.24 +/- 0.16), 10(-3.84 +/- 0.16) and 10(-4.07 +/- 0.07), respectively at I = 0.1 M and 25 degrees C. HNBO(6)Q exhibited very high selectivity toward gallium(III) in the presence of aluminum(III). Even in the presence of a 100 fold excess of aluminum(III) to gallium(III) (1.43 x 10(-5) M), gallium(III) was completely extracted and the distribution ratio of aluminum(III) was found to be less than 2.0 x 10(-3).     

Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures

Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.     

Exploratory Investigation of New SHG Materials Based on Galloborates

Three new galloborates, namely, GaB(5)O(8)(OH)(2)(en)(2)·H(2)O (1), LiGa(OH)(BO(3))(H(2)O) (2), and Rb(2)Ga(B(5)O(10))(H(2)O)(4) (3), have been synthesized by hydrothermal reactions. Compound 1 is the first example of a galloborate that contains an organic component. It crystallizes in space group P2(1)/c, and its crystal structure exhibits an infinite zigzag chain consisting of [B(5)O(8)(OH)(2)](3-) anions and GaO(2)N(4) octahedra interconnected via corner sharing. Compound 2 crystallizes in space group P31c with a layered structure composed of GaO(4), LiO(4), and BO(3) building units. Compound 3 belongs to chiral space group C222(1); the basic building blocks of the structure are the [B(5)O(10)](5-) cluster anion and GaO(4) tetrahedron, which are interconnected to form a three-dimensional network with tunnels of Ga2B6 eight-membered rings (8-MRs) which are filled by Rb(+) cations and lattice water molecules. Interestingly, Rb(2)Ga(B(5)O(10))(H(2)O)(4) displays a moderate second-harmonic generation (SHG) response comparable to that of KH(2)PO(4) (KDP), and it is phase matchable. Band structure and optical property calculations for Rb(2)Ga(B(5)O(10))(H(2)O)(4) based on DFT methods were also performed.     

Interactions between GaO4Al12(OH)24(H2O)12(7+) and cellulosic materials

The adsorption qualities of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+), a polycation with ε-Keggin structure, and its stability in contact with anionic cellulosic materials, was investigated under different concentration and ionic strength conditions. The cellulosic materials employed were two different fully bleached fibre materials, carboxyl methyl cellulose (CMC), and a spin-coated cellulose model surface. As analytical techniques, pH-measurements, potentiometric titrations, ICP-OES, QCM-D, equilibrium calculations and Extended X-ray Absorption Fine Structure (EXAFS) were used. The adsorption is substantial and the addition of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) to a fibre suspension results in a rapid decrease in pH, followed by a small and slow increase in pH. This behaviour can be explained as due to a rapid and strong (log β>2) equilibrium adsorption of intact GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) ions, followed by a slow, and minor, 3-8%, decomposition into different monomers. Alternative layer by layer adsorption of this ion, and CMC, on a spin-coated cellulose model surface constitutes further evidence for the strong interactions between the anionic cellulose materials and GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+). It is shown that the adsorption observed could not be described as due to an unspecific Donnan adsorption behaviour, neither of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) nor Ga and Al monomers, and specific surface complex formation is therefore discussed and applied. The (≡COO)(7)GaO(4)Al(12)(OH)(24)(H(2)O)(12) species found to explain the pH- and metal adsorption data should be considered strictly as a stoichiometric entity.     

Hydrothermal Synthesis and Crystal Structure of a Cadmium(Ⅱ) Polymer with One-dimensional Chain Structure: [Cd(bpy)(BDC)]n·nbpy

A metal-organic coordination polymer [Cd(bpy)(BDC)]n·nbpy (bpy = 2,2'-bipyri- dine, H2BDC = terephthalic acid) has been hydrothermally synthesized and structurally characteri- zed by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. The complex crystallizes in monoclinic, space group C2/c with a = 15.723(5), b = 21.695(5), c = 7.576(5)(A), β = 116.171(7)o, V = 2319.3(18)(A)3, C28H20CdN4O4, Mr = 588.88, Dc = 1.686 g/cm3, μ(MoKα) = 0.987 mm(1, F(000) = 1184, Z = 4, the final R = 0.0464 and wR = 0.0831 for 1882 observed reflections (Ⅰ ＞ 2σI)). It exhibits a three-dimensional network with channels constructed from one-dimensional coordination chains via C-H…O hydrogen bonds and significant aromatic π-π stacking interactions.     

A new Al-MOF based on a unique column-shaped inorganic building unit exhibiting strongly hydrophilic sorption behaviour

The new Al-based metal-organic framework [Al(13)(OH)(27)(H(2)O)(6)(BDC-NH(2))(3)Cl(6)(C(3)H(7)OH)(6)] denoted CAU-6 (CAU = Christian-Albrechts-Universit?t) was solvothermally synthesized in 2-propanol and was thoroughly characterized. The framework structure exhibits a unique column-shaped inorganic building unit, which is based on stacked, corner-sharing Al(13)-clusters. The compound exhibits unprecedented hydrophilicity for metal-organic frameworks.     

An in-depth correlation of perturbation of the organic-inorganic interface topology,electronic structure,and transport properties within beta''-(BEDT-TTF)(4) x (guest)(n) x [Re(6)Q(6)Cl(8)], (Q=S,Se)

An in-depth analysis of a set of 21 layered structures of metallic pseudopolymorphs of general formulation, beta'-(BEDT-TTF)(4) x (guest)(n) x [Re(6)Q(6)Cl(8)], (BEDT-TTF=bis-ethylenedithiotetrathiafulvalene; Q = S, Se; guest = H(2)O, 1,4-dioxane, THF, CCl(4), C(2)H(5)OH, CHCl(3), CH(2)ClI, CH(2)ClBr, CH(2)Cl(2), CH(2)OH-CH(2)OH, C(5)H(5)N, CH(3)COCH(3), 2-hydroxy-tetrahydrofuran, CH(3)CN, CS(2), C(6)H(6)), with diverse low-temperature behaviors, which differ solely by the nature of the cosolvent molecule selectively included during the electrocrystallization process, reveals a precise set of weak HO-H...Cl-mu-Re, (C-H)(BEDT-TTF)...Cl-mu-Re, C-H...O(guest), (C-H)(guest)...Cl-mu-Re hydrogen bonds at the organic-inorganic interface, none of which dominates any of the others and whose balance is adjusted upon substitution of one guest molecule by another. The electronic structure of the host adjusts to the weak perturbation imposed by exchanging the guest molecules and by balancing the former interfacial interactions; this correlates to a net activation of up to 0.1 eV of the energy of the HOMO level of one of the two donors, while keeping the pattern of HOMO-HOMO intermolecular interactions in the donor layer essentially unaltered. It is suggested that this controls the stability of the metallic state at low temperature or the occurrence of a metal-to-insulator phase transition for particular guests along the series. It is concluded that by allowing for numerous tiny modifications at the organic-inorganic interface within a single, robust host structure, one sees a concerted, inherently weak structural response of the system that is proportional to the magnitude of the underlying, equally weak activation of the HOMO energy of a fraction of the pi-donor molecules within the slabs; this has a sizeable influence on the macroscopic transport properties of the system.     

Syntheses, structures, and photoluminescence of a novel class of d10 metal complexes constructed from pyridine-3,4-dicarboxylic acid with different coordination architectures

Two novel d(10) metal coordination polymers [Zn(PDB)](n)() (1) and [Cd(3)(PDB)(2)(OH)(2)(H(2)O)(2)](n)() (2) (H(2)PDB = pyridine-3,4-dicarboxylic acid) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, TG analysis, and single-crystal X-ray diffraction. Crystal data for 1: C(7)H(3)NO(4)Zn, orthorhombic Pna2(1), a = 8.423(17) A, b = 6.574(13) A, c = 12.899(3) A, Z = 4. Crystal data for 2: C(14)H(12)N(2)O(12)Cd(3), monoclinic C2/c, a= 20.130(4) A, b = 6.692(13) A, c = 13.081(3) A, beta = 102.78(3) degrees, Z = 4. Both compounds exhibit novel three-dimensional frameworks. Compound 1 not only possesses a one-dimensional rectangular channel but also contains infinite double-stranded helical chains. Compound 2 has two different types of channels, one being built up from pyridine rings and [CdO(5)N] and [CdO(6)] building units and the other being constructed from pyridine rings and [CdO(5)N] building units. Furthermore, both compounds show strong photoluminescence properties at room temperature.     

Poly­[[bis­(pyridine‐κN)copper(II)]‐μ3‐5‐hydroxy­isophthalato‐κ3O:O′:O′′]

In the title compound, [Cu(C₈H₄O₅)(C₅H₅N)₂]_n or [Cu(OH‐BDC)(py)₂]_n (where OH‐H₂BDC is 5‐hydroxy­isophthalic acid and py is pyridine), the Cu atoms are coordinated by two N atoms from the pyridine ligands and by three O atoms from hydroxy­isophthalate ligands in a highly distorted triangular bipyramidal environment, with Cu—O distances in the range 1.941 (4)–2.225 (5) Å and Cu—N distances of 2.014 (6) and 2.046 (6) Å. The [Cu(OH‐BDC)]_n two‐dimensional network is built up from interlocking 22‐, 15‐ and eight‐membered rings via sharing of Cu atoms and O—H⋯O hydrogen bonds. Consolidation of the packing structure is achieved by edge‐ or point‐to‐face C—H⋯π interactions and offset or slipped π–π stacking interactions.     

Syntheses, topological analyses, and NLO-active properties of new Cd(II)/M(II) (M = Ca, Sr) metal-organic frameworks based on R-isophthalic acids (R = H, OH, and t-Bu)

Solvothermal syntheses of Cd(NO(3))(2)·4H(2)O and R-isophthalic acids (R = H, OH and t-Bu) in the presence of Ca(II) or Sr(II) lead to four new three-dimensional Cd(II)/Ca(II) or Cd(II)/Sr(II) heterometallic frameworks: [CdCa(m-BDC)(2)(DMF)(2)] (1), [CdSr(2)(m-BDC)(2)(NO(3))(2)(DMF)(4)] (2), [CdCa(OH-m-BDC)(2)(H(2)O)(2)]·2Me(2)NH (3), and (Me(2)NH(2))(2)[Cd(2)Ca(Bu(t)-m-BDC)(4)] (4) (m-H(2)BDC = isophthalate, OH-m-H(2)BDC = 5-hydroxyisophthalate and Bu(t)-m-H(2)BDC = 5-butylisophthalate). All of these compounds except for 4 crystallize in acentric (or chiral) space groups and the bulk materials for 1 and 3 display strong powder SHG efficiencies, approximately 1.54 and 2.31 times than that of a potassium dihydrogen phosphate (KDP) powder. Topological analyses show that 1 and 2 have structures with sxb and dia topologies, respectively, while both 3 and 4 exhibit pcu topological nets when the metal carboxylate clusters are viewed as nodes. The fluorescence properties and thermal stabilities for these compounds are also investigated.     

Convenient synthesis of aluminum and gallium phosphonate cages

The reactions of AlCl 3.6H 2O and GaCl 3 with 2-pyridylphosphonic acid (2PypoH 2) and 4-pyridylphosphonic acid (4PypoH 2) afford cyclic aluminum and gallium phosphonate structures of [(2PypoH) 4Al 4(OH 2) 12]Cl 8.6H 2O ( 1), [(4PypoH) 4Al 4(OH 2) 12]Cl 8.11H 2O ( 2), [(2PypoH) 4Al 4(OH 2) 12](NO 3) 8.7H 2O ( 3), [(2PypoH) 2(2Pypo) 4Ga 8Cl 12(OH 2) 4(thf) 2](GaCl 4) 2..8thf ( 4), and [(2PypoH) 2(2Pypo) 4Ga 8Cl 12(OH 2) 4(thf) 2](NO 3) 2.9thf ( 5). Structures 1- 3 feature four aluminum atoms bridged by oxygen atoms from the phosphonate moiety and show structural resemblance to the secondary building units found in zeolites and aluminum phosphates. The gallium complexes, 4 and 5, have eight gallium atoms bridged by phosphonate moieties with two GaCl 4 (-) counterions present in 4 and nitrate ions in 5. The cage structures 1- 3 are interlinked by strong hydrogen bonds, forming polymeric chains that, for aluminum, are thermally robust. Exchange of the phosphonic acid for the more flexible 4PyCH 2PO 3H 2 afforded a coordination polymer with a 1:1 Ga:P ratio, {[(4PyCH 2PO 3H)Ga(OH 2) 3](NO 3) 2.0.5H 2O} x ( 6). Complexes 1- 6 were characterized by single-crystal X-ray diffraction, NMR, and mass spectrometry and studied by TGA.     

Novel flexible frameworks of porous cobalt(II) coordination polymers that show selective guest adsorption based on the switching of hydrogen-bond pairs of amide groups

Four porous crystalline coordination polymers with two-dimensional frameworks of a double-edged axe-shaped motif, [[Co(NCS)(2)(3-pia)(2)] x 2 EtOH.11 H(2)O](n) (1 a), [[Co(NCS)(2)(3-pia)(2)] x 4 Me(2)CO](n) (3 a), [[Co(NCS)(2)(3-pia)(2)] x 4T HF](n) (3 b) and [[Co(NCS)(2)(3-pna)(2)](n)] (5), have been synthesized by the reaction of cobalt(II) thiocyanate with N-(3-pyridyl)isonicotinamide (3-pia) or N-(3-pyridyl)nicotinamide (3-pna). X-ray crystallographic characterization reveals that adjacent layers are stacked such that channels are created, except in 5. The channels form a hydrogen-bonded interior for guest molecules; in practice, 1 a contains ethanol and water molecules as guests in the channels with hydrogen bonds, whereas 3 b (3 a) contains tetrahydrofuran (acetone) molecules. In 1 a, the "double-edged axe-shaped" motifs in adjacent sheets are not located over the top of each other, while the motifs in 3 b stack so perfectly as to overlap each other in an edge-to-edge fashion. This subtle change in the three-dimensional framework is associated with the template effect of the guests. Compound 5 has no guest molecules and, therefore, the amide groups in one sheet are used for hydrogen-bonding links with adjacent sheets. Removal of the guest molecules from 1 a and 3 b (3 a) causes a structural conversion accompanied by a color change. Pink 1 a cannot retain its original framework and changes into a blue amorphous compound. On the other hand, the framework of pink 3 b (3 a) is transformed to a new crystalline framework of violet 4. Interestingly, 4 reverts to the original pink crystals of 3 b (3 a) when it is exposed to THF (or acetone) vapor. Spectroscopic measurements (visible, EPR, and IR) provide a clue to the crystal-to-crystal transformation; on removal of the guests, the amide groups are used to form the beta sheet-type hydrogen bonding between the sheets, and thus the framework withstands significant stress on removal of guest molecules. This mechanism is attributed to the arrangement of the adjacent sheets so suited in regularity that the beta sheet-type structure forms efficiently. The apohost 4 does not adsorb cyclopentane, showing a guest selectivity that, in addition to size, hydrogen-bonding capability is required for the guest molecules. The obtained compound is categorized as a member of a new generation of compounds tending towards functional porous coordination polymers.