Hydrothermal synthesis, crystal structure and luminescence of four novel metal-organic frameworks

Using the principle of crystal engineering, four novel metal-organic coordination polymers, {[Cd₁(nic)2(H₂O)]2[Cd₂(nic)2(H₂O)2]}_n (1), [Cd₂(fma)2(phen)2]_n (2), [Cd(fma)(bipy)(H₂O)]_n (3) and [Zn(mal)(bipy)·3H₂O]_n (4) (nic=nicotinate, fma=fumarate, mal=malate, phen=phenanthroline, bipy=2,2′-bipyridine) have been synthesized by hydrothermal reaction of M(CH₃COO)2·2H₂O (M=Zn, Cd) with nicotinic acid, fumaric acid and cooperative L (L=phen, bipy), respectively. X-ray analysis reveals that complex 1 possesses an unprecedented two-dimensional topology structure constructed from three-ply-like layers, complex 2 is an infinite 2D undulating network, complex 3 is a 1D zigzag chain and complex 4 belongs to a 1D chain. The results indicate a transformation of fumarate into malate during the course of hydrothermal treatment of complex 4. The photophysical properties have been investigated with luminescent excitation and emission spectra.     

Structures and H2 adsorption properties of porous scandium metal-organic frameworks

Two new three-dimensional Sc(III) metal-organic frameworks {[Sc(3)O(L(1))(3)(H(2)O)(3)]·Cl(0.5)(OH)(0.5)(DMF)(4)(H(2)O)(3)}(∞) (1) (H(2)L(1)=1,4-benzene-dicarboxylic acid) and {[Sc(3)O(L(2))(2)(H(2)O)(3)](OH)(H(2)O)(5)(DMF)}(∞) (2) (H(3)L(2)=1,3,5-tris(4-carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar [Sc(3)(O)(O(2)CR)(6)] building block featuring three Sc(III) centres joined by a central μ(3)-O(2-) donor. Each Sc(III) centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the μ(3)-O(2-) donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350 °C. The desolvated materials 1a and 2a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to Sc(III), show BET surface areas based upon N(2) uptake of 634 and 1233 m(2) g(-1), respectively, and pore volumes calculated from the maximum N(2) adsorption of 0.25 cm(3) g(-1) and 0.62 cm(3) g(-1), respectively. At 20 bar and 78 K, the H(2) isotherms for desolvated 1a and 2a confirm 2.48 and 1.99 wt% total H(2) uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59 kJ mol(-1) at zero surface coverage for 1a and 2a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2b. Framework 2b shows an enhanced BET surface area of 1511 m(2) g(-1) and a pore volume of 0.76 cm(3) g(-1), with improved H(2) uptake capacity and a higher heat of H(2) adsorption. At 20 bar, H(2) capacity increases from 1.99 wt% in 2a to 2.64 wt% for 2b, and the H(2) adsorption enthalpy rises markedly from 2.59 to 6.90 kJ mol(-1).     

A 4-fold interpenetrated metal-organic diamondoid framework: synthesis,crystal structure,and properties

The coordination polymer, [Cu₂(bpp)₄Cl₂]Cl₂, was prepared by self-assembly of benzo[f] [1,10]phenanthroline-6,7-dicarboxylic acid and bpp [bpp = 1,3-bis(4-pyridyl)propane] with CuCl₂·2H₂O, and determined by X-ray crystallographic diffraction, IR spectrum, and thermal analysis. The complex features a 3-D 4-fold interpenetrated metal–organic framework with diamondoid topology. There are two sets of diamondoid frameworks independently constructed by bpp bridging the same copper centers, and the two sets of diamondoid frameworks interpenetrate one another to form an interesting 4-fold interpenetrating 3-D architecture.     

Construction of metal-organic frameworks: versatile behaviour of a ligand containing mono- and bidentate coordination sites

Five new coordination polymers based on a new 2,2'-bipyridine derived ligand N,N'-bis(pyridin-4-yl)-2,2'-bipyridine-5,5'-dicarboxamide (=L) are reported herein. Isostructural three-dimensional coordination polymers with a rare (4,6)-connected network of {4(4).6(2)}(3){4(6).8(9)}(2) topology were synthesised from Cu(NO(3))(2), Zn(NO(3))(2) or a mixture of Cu(NO(3))(2)/Fe(BF(4))(2) with L in complexes {[Cu(5)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (1), {[Zn(5)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (2) and {[Fe(x)Cu(y)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (3; where x+y=5). Complexes with two-dimensional grid structures resulted from treatment with CoCl(2) or Cd(NO(3))(2) with L in complexes {[CoLCl(2)]·DMF}(∞) (4) and {CdL(NO(3))(2)}(∞) (5).     

Design and generation of extended zeolitic metal-organic frameworks (ZMOFs): synthesis and crystal structures of zinc(II) imidazolate polymers with zeolitic topologies

Attempts to create metal-organic frameworks (MOFs) with zeolitic topologies, metal (zinc(II) and cobalt(II)) imidazolates have repeatedly been used as the metal-organic motifs of inorganic silicate analogues. By modulating the synthetic strategy based on the solvothermal and liquid diffusion method, seven further MOFs (including at least three zeolitic MOFs) of zinc(II) imidazolates, [Zn(im)2.x G] (G=guest molecule, x=0.2-1) 1 a-7 a, have been successfully synthesized. Of these, 1 a-3 a are isostructural with the previously reported cobalt analogues 1 b-3 b, respectively, while 4 a-7 a are new members of the metal imidazolate MOF family. Complex 4 a exhibits a structure related to silicate CaAl2Si2O8 of CrB4 topology, but with a higher network symmetry; complex 5 a has a structure with zeolitic DFT topology that was discovered in zeolite-related materials of DAF-2, UCSB-3, and UCSB-3GaGe; complex 6 a demonstrates an unprecedented zeolite-like topology with one dimensional channels with 10-rings; and 7 a displays a structure of natural zeolite GIS (gismondine) topology. All of these polymorphous MOFs were created only by using certain solvents as structure-directing agents (SDAs). Further extensive metal-organic frameworks with zeolitic topologies can be envisaged if other solvents were to be used.     

Synthesis, characterization, properties and crystal structure of heterometallic 1D coordination polymers{[CuLZn· CuLZn(H2O)]·H2O}n

Copper-zinc heterometallic 1D chain coordination polymer has been synthesized and characterized by elemental analysis, and IR spectra etc. The crystal structure was determined by single-crystal X-ray diffraction analyses. The title complex is 1 D chain coordination polymer with the chemical formula {[CuLZn·CuLZn(H2O)]·H2O}n, where H4L=N-(2-hydroxybenzamido)-N'-(3-carboxy-Isalicylidene)ethylenediamine. Its structural unit is comprosed of two tetranuclear cycles formed by two dissymmetrical tetranuclear units. These units polymerized each other to form 1D chain coordination polymer.     

Structural changes and coordinatively unsaturated metal atoms on dehydration of honeycomb analogous microporous metal-organic frameworks

Porous metal-organic framework compounds with coordinatively unsaturated metal sites on the inner surface of the pores promise to be valuable adsorbents and catalyst systems, either in industrial applications or as model systems to study interactions with guest molecules. The dehydration process of two isostructural microporous coordination polymers, [M2(dhtp)(H2O)2].8 H2O, termed CPO-27-M (M=Co, Zn; H(4)dhtp=2,5-dihydroxyterephthalic acid) was investigated by in situ variable temperature X-ray diffraction. Both compounds contain accessible coordination sites at the metal after complete removal of the solvent. However, despite the analogy of their crystal structures, they behave differently during dehydration. For CPO-27-Co, water desorption is a smooth topotactic process of second order with no concomitant space group change and no increase in microstrain, which is beneficial for the applicability of the material. Removal of the water propagates from the center of the channels outwards. The coordinating water molecule at the metal desorbs only when almost all the bulk water in the pores has disappeared. In contrast, discontinuities in the powder pattern of CPO-27-Zn indicate the occurrence of first-order transitions. The crystal structures of four of the five individual phases could be determined. The structure of the intermediate phase occurring just before the framework is completely evacuated was elusive in respect to full structure solution and refinement, but it is most probably related to the removal of the axis of threefold symmetry. The zinc-based material experiences a significant amount of strain.     

Synthesis, characterization, properties and crystal structure of heterometallic 1D coordination polymers {[CuLZn·CuLZn(H2O)]·H2O}n

Copper-zinc heterometallic 1D chain coordination polymer has been synthesized and characterized by elemental analysis, and IR spectra etc. The crystal structure was determined by single-crystal X-ray diffraction analyses. The title complex is 1D chain coordination polymer with the chemical formula {[CuLZn·CuLZn(H₂O)]·H₂O}_n, where H₄L=N-(2-hydroxybenzamido)-N′-(3-carboxylsalicylidene)ethylenediamine. Its structural unit is comprosed of two tetranuclear cycles formed by two dissymmetrical tetranuclear units. These units polymerized each other to form 1D chain coordination polymer.     

New chain polymer [Yb(tpa)(H2O)2Co(CN)6]n · 7n H2O: synthesis,structure, and magnetic characteristics

The 3d– 4f heterometallic polymeric complex, namely [Yb(tpa)(H₂O)₂Co(CN)₆]_n·7n H₂O [tpa = tris(2-pyridylmethyl)- amine], was synthesized and characterized. Its polymer structure is formed of [Yb(tpa)(H₂O)₂Co(CN)₆] chains and crystallization water molecules with a two-capped trigonal prism Yb³⁺ coordination polyhedron; the Yb³⁺ coordination number is 8, and the coordination site is YbN₆O₂. Magnetic characteristics indicate that the complex exhibits the properties of a single-chain magnet with a magnetization reversal barrier(!E/k_B) of 42 K.     

Manganese(II) Coordination Polymers [{Mn(tren)}(As2Se4)] and [{Mn(tren)}(As4Se7)] with Infinite Selenidoarsenate(III) Chains $^{1}_{\infty}\rm [AsSe_{2}^{-}]$ and $^{1}_{\infty}\rm [As_{4}Se_{7}^{2-}]$

Solvothermal reaction of [MnCl₂(tren)] with elemental As and Se at 1:1:2 and 1:6:12 molar ratios in H₂O/tren (10:1) affords the 1D coordination polymers [{Mn(tren)}(As₂Se₄)] ( 1 ) and [{Mn(tren)}(As₄Se₇)] ( 2 ), respectively. 1 contains vierer infinite chains, which coordinate [(tren)Mn]²⁺ fragments through every second terminal Se atom of their corner‐sharing pyramidal AsSe₃ building units. The double chains of compound 2 are related to the chains 1 by a simple rearrangement of the connectivity pattern between the participating AsSe₃ pyramids and contain condensed centrosymmetric As₈Se₈ and As₄Se₄ rings.     

Cadmium-Inspired Self-Polymerization of {LnIIICd2} Units: Structure,Magnetic and Photoluminescent Properties of Novel Trimethylacetate 1D-Polymers (Ln = Sm,Eu, Tb,Dy, Ho,Er, Yb)

A series of heterometallic carboxylate 1D polymers of the general formula [Ln^IIICd₂(piv)₇(H₂O)₂]_n·nMeCN (Ln^III = Sm (1), Eu (2), Tb (3), Dy (4), Ho (5), Er (6), Yb (7); piv = anion of trimethylacetic acid) was synthesized and structurally characterized. The use of Cd^II instead of Zn^II under similar synthetic conditions resulted in the formation of 1D polymers, in contrast to molecular trinuclear complexes with Ln^IIIZn₂ cores. All complexes 1–7 are isostructural. The luminescent emission and excitation spectra for 2–4 have been studied, the luminescence decay kinetics for 2 and 3 was measured. Magnetic properties of the complexes 3–5 and 7 have been studied; 4 and 7 exhibited the properties of field-induced single-molecule magnets in an applied external magnetic field. Magnetic properties of 4 and 7 were modelled using results of SA-CASSCF/SO-RASSI calculations and SINGLE_ANISO procedure. Based on the analysis of the magnetization relaxation and the results of ab initio calculations, it was found that relaxation in 4 predominantly occurred by the sum of the Raman and QTM mechanisms, and by the sum of the direct and Raman mechanisms in the case of 7.     

Hydrothermal synthesis and crystal structure of two new lanthanide coordination polymers with 1,2-phenylenediacetate

Two new compounds {[Ln₂(1,2-pda)₃(H₂O)₂]·?2H₂O} _n (1,2-H₂pda?=?1,2-phenylenediacetic acid, Ln?=?Tb, 1; Ho, 2) were prepared by hydrothermal reaction and characterized by X-ray crystallography. The Ln³⁺ is nine-coordinate by eight oxygen atoms of six 1,2-pda ligands and one oxygen of water. Ln³⁺ ions are bridged by 1,2-pda ligands via bridging/chelating-bridging pentadentate and chelating-bridging/chelating-bridging hexadentate coordination to form 3-D framework structures. Complex 1 emits strong green fluorescence corresponding to ⁵D₄???⁷F_j (j?=?6–3) transitions of the Tb³⁺.     

两个含有平行交替链的新型二氰胺配位高聚物: {Mn(dmpz)[N(CN)2]2}2和{Cu(dmpz)[N(CN)2]2}2

Two new dicyanamide coordination polymers, {Mn(dmpz)[N(CN)2]2}2 (1) and {Cu(dmpz)[N(CN)2]2}2 (2)(dmpz=3,5-dimethylpyrazole), were synthesized and characterized by single crystal X-ray diffraction analysis and IR spectroscopy. In 1 and 2 the metal ions have two different coordination modes, where one is coordinated to four dicyanamide anions and two monodentate dmpz molecules to form a slightly distorted octahedral geometry, while the other adopts octahedral geometry, surrounded by four nitrile N atoms and two amide N atoms of the dicyanamide anions. Both complexes contain two alternating chains that are parallel to each other.     

Lead(II) coordination frameworks with 3-fluorophthalic acid: hydrothermal synthesis,crystal structure,and luminescence

Hydrothermal reactions of Pb(NO₃)₂ and 3-fluorophthalic acid (H₂Fpht) in the absence or presence of 2,2′-bipyridine (bpy) gave two coordination polymers: Pb₅(Fpht)₄(Fba)₂ (1) and [Pb₂(Fpht)₂(bpy)(H₂O)]·3H₂O (2). The 3-fluorobenzoic acid (HFba) results from an in situ decarboxylation of H₂Fpht. Solid 1 displays a 2-D structure, comprising center-related hexanuclear [Pb₃(COO)₆]₂ units. There are three crystallographically different Pb(II) ions and two different ligands, Fpht and Fba. The Fpht ligands adopt μ_6?:?η⁵η³ and μ_6?:?η³η⁴ unusual bridging coordination modes. A 3-D supramolecular architecture is formed via C–H?F hydrogen bonds. Solid 2 possesses a 1-D chain structure, comprising center-related tetranuclear [Pb₂(COO)₄]₂ units. There are two crystallographically different Pb(II) ions. The Fpht ligands adopt μ_3?:?η²η³ and μ_4?:?η³η³ bridging coordination. The free water molecules form (H₂O)₃ clusters to link the 1-D chain by hydrogen bonds. A 3-D supramolecular assembly is constructed via hydrogen bonds between the free water and the F of Fpht ligands. Fluorescence of the complexes originates from π*–π transitions of the ligands.     

Facile synthesis of interstitial metal nitrides with the filled β-manganese structure

A new family of nitrides, Ni_2−xM′_xMo₃N (M′=Co or Pd; 0?x?1.5), has been prepared pure by nitridation of commercially available crystalline metal oxides under reducing conditions (10% H₂ in N₂). The simple synthesis employs standard solid-state techniques and does not require the preparation of reactive precursors. Substitution of Ni by Co or Pd leads to a linear increase of the unit cell volume with composition. The temperature, composition, and magnetic-field dependence of the molar magnetisation suggest that the introduction of Co, but not Pd, increases the degree of electron localisation in Ni_2−xM′_xMo₃N. The same synthetic method has also lead to the formation, in mixtures, of the new phases π-Co₂Mo₃N and Pd₂N.     

Synthesis,structure, and properties of trinuclear pivalate {Zn2Eu} complexes with N-donor ligands

New luminescent heterometallic complexes of Eu³⁺ and Zn²⁺ were synthesized: Zn₂Eu(NO₃)(Piv)₆(L)₂ (Piv is pivalate anion, L = MeCN (1), 2,3-lutidine (2), 2,2′-bpy (3)) and [Zn₂(Piv)₃(2,2′-bpy)₂][ZnEu(NO₃)₃(Piv)₃(2,2′-bpy)] (4). In the case of 2,2′-bpy, the order of mixing of the reagents ([Zn(Piv)₂] _n , Eu(NO₃)₃·6H₂O, and 2,2′-bpy) affects the composition of the final reaction product: the reaction of [Zn(Piv)₂] _n and Eu(NO₃)₃·6H₂O (in the ratio Zn : Eu = 3 : 1) in MeCN affords complex 1 and the subsequent addition of 2,2′-bpy (Zn : L = 1 : 1) affords complex 3. Complex 4 is formed in the reaction of [Zn(Piv)₂] _n and 2,2′-bpy (Zn : L = 1 : 1) in MeCN followed by the addition of Eu(NO₃)₃·6H₂O (Zn : Eu = 3 : 1). The luminescence spectra of compounds 1–4 (Zn : Eu = 3 : 1) exhibit metal-centered luminescence of Eu³⁺. The most efficient ligand-antenna is 2,2′-bpy, which is due to the optimum position of the triplet level of this ligand.     

Pillaring of CdCl2-like layers in lanthanide metal-organic frameworks: synthesis, structure, and photophysical properties

A hydrothermal reaction of lanthanide salts, pyridine-2,3-dicarboxylic acid, benzene-1,4-dicarboxylic acid, and water gave rise to a new series of three-dimensional mixed carboxylates (homocyclic and heterocyclic) of lanthanides with the general formula [M2(H2O)4][{C5H3N(COO)2}2{C6H4(COO)2}], M=La (I), Pr (II), and Nd (III). The structure consists of M2O14N2 dimeric units connected by pyridine-2,3-dicarboxylate moieties to form two-dimensional layers that are pillared by terephthalate units. The structures also possess two co-ordinated water molecules, which are arranged to form one-dimensional helical chains and can be reversibly adsorbed. The connectivity within the layers closely resembles that of the CdCl2 layered structure with 3(6) topology. To the best of our knowledge, this is the first observation of CdCl2 topology in lanthanide metal-organic framework compounds. Partial substitution of La3+ in I by Eu3+ and Tb3+ (2 and 4 %) gives rise to characteristic red/pink or green emission, which suggests a ligand-sensitized metal-centered emission. The Nd compound III shows interesting UV and blue emission through an up-conversion process.     

Metal imidazolato polymers: synthesis, characterization and crystal structure of new silver(I) triphenylphosphine derivatives

When the polymeric complex [Ag(im)]_n (Him = imidazole) is reacted with PPh₃ (PPh₃ = triphenylphosphine), it yields the [Ag₂(μ₂-im)₂(PPh₃)₃]_n and [Ag(μ₂-im)(PPh₃)₂]_n species, shown to contain wavy chains of metal ions, singly bridged by N,N′-exo-bidentate imidazolate ligands. The former, crystallised as the CH₂Cl₂ solvate, contains two non-equivalent silver(I) ions, differing in the number of coordinated phosphines (one, in trigonal planar stereochemistry, or two, having tetrahedral geometry). The latter has a unique independent silver(I) ion in a tetrahedral environment, with two coordinated PPh₃ ligands. The reactivity of known silver(I) azolates with PPh₃, as well as the solution behaviour and (when available) the crystal structures of the corresponding derivatives are taken into consideration for a due comparison.     

Two novel lanthanide(III) organic frameworks based on a biphenyltetracarboxylate ligand: synthesis,structure and magnetic and luminescence properties

Two new two‐dimensional lanthanide coordination polymers, namely poly[[tetra‐μ₂‐acetato‐tetraaquabis(μ₄‐biphenyl‐3,3′,5,5′‐tetracarboxylato)tetrakis(dimethylacetamide)tetraterbium(III)] pentahydrate], {[Tb₄(C₁₆H₆O₈)₂(C₂H₃O₂)₄(C₄H₉NO)₄(H₂O)₄]·5H₂O}_n, (1), and poly[[tetra‐μ₂‐acetato‐tetraaquabis(μ₅‐biphenyl‐3,3′,5,5′‐tetracarboxylato)tetrakis(dimethylacetamide)tetraeuropium(III)] tetrahydrate], {[Eu₄(C₁₆H₆O₈)₂(C₂H₃O₂)₄(C₄H₉NO)₄(H₂O)₄]·4H₂O}_n, (2), have been synthesized from biphenyl‐3,3′,5,5′‐tetracarboxylic acid (H₄bpt) and Ln(NO₃)₃·6H₂O (Ln = Tb and Eu) under solvothermal conditions. Single‐crystal X‐ray structure analysis shows that the two compounds are isostructural and crystallize in the monoclinic P2₁/n space group. The crystal structures are constructed from bpt⁴⁻ ligands (as linkers) and {Ln₂(μ₂‐CH₃COO)₂} building units (as nodes), which topological analysis shows to be a (4,6)‐connected network with sql topology. Compounds (1) and (2) have been characterized by elemental analysis, IR spectroscopy, powder X‐ray diffraction (PXRD), thermogravimetric analysis (TGA) and fluorescence analysis in the solid state. In addition, a magnetic investigation shows the presence of antiferromagnetic interactions in compound (1).     

Synthesis and structural investigation of two metal-organic frameworks constructed from alkaline earth metal cations and organic ligand 5-nitroisophthalic acid (5-NO<Subscript>2</Subscript>-H<Subscript>2</Subscript>BDC)

Two supermolecular co-ordination polymers [M(5-NO₂-BDC)(H₂O)₆] [M = Sr(1), Ba(2)] were prepared by the assembly of alkaline earth metal cations and symmetric organic ligand 5-NO₂-H₂BDC, respectively. These two complexes have been characterized with the aid of elemental analysis, thermal analysis, infrared spectroscopic and X-ray crystallography. Both 1 and 2 have a similar 3D flowerlike supramolecular assembled by multiple interpenetration of the 1D chains where 12-membered rings share common C–O–M edges with each other extended by O–H···O hydrogen bonds. The co-ordination geometry around M (II) ions could be described as distorted tricapped trigonal prism arrangements.