Single-crystal-to-single-crystal transformation from 1 D staggered-sculls chains to 3 D NbO-type metal-organic framework through [2+2] photodimerization

A new approach to synthesize 3D structures through a [2+2] photodimerization process has been carried out by transforming two isostructures of 1D staggered-sculls chains [M(1,2-chdc)(bpe)(2)(H(2)O)(2)]?H(2)O (M = Zn, Mn) into 3D?NbO-type metal-organic frameworks through UV irradiation in single-crystal-to-single-crystal mode. (see figure; bpe = trans-1,2-(bis(4-pyridyl)ethene, chdc =cyclohexanedicarboxylate).     

A bioinspired synthetic approach for building metal-organic frameworks with accessible metal centers

We demonstrate how a bioinspired synthetic approach can help organic linkers distinguish between different types of metal centers in metal-organic frameworks (MOFs). Modification of an organic building unit with methyl groups enables the unit to selectively coordinate to one of the two metal sites present in the MOFs. We report four new porphyrin-based, pillared-paddlewheel frameworks: PPF-11-Zn/Zn, -Co/Co, -Mn/Zn, and -Fe/Zn, where the first and second metals indicate the metal center for the porphyrin core and paddlewheel cluster, respectively. These compounds exhibit 3D MOFs in which 2D layers are pillared by a sterically controlled bipyridine, leaving the metal centers inside the porphyrin structurally unconnected.     

Influence of ligand field stabilization energy on the elastic properties of multiferroic MOFs with the perovskite architecture

We report the mechanical properties of four isostructural metal-organic frameworks (MOFs) that adopt the ABX(3) perovskite topology: [(CH(3))(2)NH(2)]M(HCOO)(3), where M = divalent Mn, Co, Ni, and Zn. Their Young's moduli were measured via single-crystal nanoindentation. We show that the mechanical stability of such isostructural frameworks with octahedral coordination increases with greater ligand field stabilization energy (LFSE).     

Supramolecular isomers of metal-organic frameworks: the role of a new mixed donor imidazolate-carboxylate tetradentate ligand

Five new metal-organic frameworks prepared from the ligand 5-bis(3-(1-imidazolyl)propylcarbamoyl)terephthalate (bipta(2-)) and transition metal salts, Zn(2+) (1), Co(2+) (2), Mn(2+) (3, 4) and Cu(2+) (5), are reported. Single crystal X-ray studies reveal that the bipta(2-) ligand acts as a tetradentate ligand and combines with four-coordinate cationic metal nodes to give four-connected framework structures. Whilst reaction of bipta(2-) with Zn(II) gives rise to a framework of diamondoid topology 1, the analogous frameworks with Co(II), Mn(II) and Cu(II) afford frameworks that incorporate square-planar nodes. Whereas 2 and 5 form frameworks of Cd(SO(4)) (cds) and square 4(4) nets (sql), respectively, reaction of Mn(II) with bipta(2-) forms two supramolecular isomers of topology cds for 3 and sql for 4.     

Synthesis, structures, and magnetic properties of transition metal compounds with 2,2'-dinitrobiphenyl-4,4'-dicarboxylate and N,N'-chelating ligands

Solvothermal reactions of Co(II), Ni(II), Zn(II) salts with 2,2'-dinitrobiphenyl-4,4'-dicarboxylate (dnpdc) and 2,2'-bipyridyl-like chelating ligands yielded five compounds formulated as [Co(dnpdc)(bipy)](n)·nH(2)O (1), [M(dnpdc)(phen)](n) (2, M = Co; 3, M = Ni; 4, M = Zn) and [Co(dnpdc)(biql)](n)·2nH(2)O (5) (bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline and biql = 2,2'-biquinoline). With bipy or phen as coligands, compounds 1-4 exhibit isomorphous 3D M(dnpdc) metal-organic frameworks in which double carboxylate bridged chains are interlinked by the backbones of the dicarboxylate ligands. The bipy or phen ligands are involved in interchain hydrogen bonding or π-π interactions to form 1D zipper-like arrays in the rhombic channels of the frameworks, playing a templating role and determining the channel dimensions. The biql coligand is too bulky for the 1D double carboxylate bridged chain and the rhombic channel. Instead, in compound 5, the dnpdc ligands link metal ions into 1D zigzag metal-organic chains and the biql ligands are arranged into 2D (6,3) arrays through extensive π-π stacking interactions. In compounds 1-3, the double carboxylate bridges in the nonplanar syn-skew conformation mediate ferromagnetic interactions along the chains, while the chelating ligands provide supramolecular pathways for interchain antiferromagnetic interactions. The π-π interactions in 5 also evoke weak antiferromagnetic interactions.     

Borromean-entanglement-driven assembly of porous molecular architectures with anion-modified pore space

A series of metal-organic frameworks based on a flexible, highly charged Bpybc ligand, namely 1?Mn?OH(-), 2?Mn?SO(4)(2-), 3?Mn?bdc(2-), 4?Eu?SO(4)(2-) (H(2)BpybcCl(2) = 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride, H(2)bdc = 1,4-benzenedicarboxylic acid) have been obtained by a self-assembly process. Single-crystal X-ray-diffraction analysis revealed that all of these compounds contained the same n-fold 2D→3D Borromean-entangled topology with irregular butterfly-like pore channels that were parallel to the Borromean sheets. These structures were highly tolerant towards various metal ions (from divalent transition metals to trivalent lanthanide ions) and anion species (from small inorganic anions to bulky organic anions), which demonstrated the superstability of these Borromean linkages. This non-interpenetrated entanglement represents a new way of increasing the stability of the porous frameworks. The introduction of bipyridinium molecules into the porous frameworks led to the formation of cationic surface, which showed high affinities to methanol and water vapor. The distinct adsorption and desorption isotherms of methanol vapor in four complexes revealed that the accommodated anion species (of different size, shape, and location) provided a unique platform to tune the environment of the pore space. Measurements of the adsorption of various organic vapors onto framework 1?Mn?OH(-) further revealed that these pores have a high adsorption selectivity towards molecules with different sizes, polarities, or π-conjugated structures.     

Anion influence on the structures of a series of copper(II) metal-organic frameworks

The main aim of the work herein presented is to investigate the influence of different anions on the overall structure of a series of metal-organic frameworks. The reactions between CuCl2, Cu(OAc)2, and CuSO4 and the two bipyridylurea ligands L1 and L2 [L1 = 1,3-bis(pyridin-4-ylmethyl)urea; L2 = 1,3-bis(pyridin-3-ylmethyl)urea; see Scheme 1 in paper] have been carried out and the crystal structure of five of the resulting metal-organic assemblies determined. These crystal structures have shown that the geometry and size of the corresponding anions together with their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Particularly interesting, because of their potential as nanoporous materials, are the assemblies obtained from the reaction between each of the two ligands (L1 and L2) and CuCl2, which yield noninterpenetrating 2D metal-organic layers made of squares of ca. 15 x 15 Angstroms. These layers stack on top of each other, producing infinite 3D channels filled with solvent molecules. The thermal stabilities of the five metal-organic frameworks prepared have been studied by means of thermogravimetric analysis. Preliminary X-ray powder diffraction studies of one of these metal-organic frameworks indicate that upon heating the assembly changes to a different crystalline structure. Interestingly, the original structure reforms upon exposure of this sample to traces of water.     

Ionothermal syntheses of six three-dimensional zinc metal-organic frameworks with 1-alkyl-3-methylimidazolium bromide ionic liquids as solvents

We have performed ionothermal reactions between Zn(NO3)2 and H3BTC in 1-alkyl-3-methylimidazolium bromide ionic liquids with the alkyl group varying from ethyl to amyl. Six 3-D metal-organic frameworks (MOFs), including two isomeric compounds [Zn3(BTC)2(H2O)2] x 2H2O (1 and 2) (H3BTC = 1,3,5-benzenetricarboxylate acid), [EMI][Zn(BTC)] (3) (E = ethyl, MI = 3-methylimidazolium), [PMI][Zn(BTC)](4) (P = propyl), [BMI]2[Zn4(BTC)3(OH)(H2O)3] (5) (B = butyl), and [AMI][Zn2(BTC)(OH)Br] (6) (A = amyl), have been synthesized and structurally characterized. Compounds 1 and 2 are isomeric compounds, in which the coordination modes of Zn atoms and the BTC3- ligands are considerably different. Compounds 3-6 crystallize with the corresponding ionic liquid cations incorporated in the frameworks. Their crystal structures show various features including various coordination geometries of Zn2+ and various bridging modes of the BTC3- ligands. The incorporated cations appear to have strong interactions with the frameworks.     

Metal-organic frameworks based on unprecedented trinuclear and pentanuclear metal-tetrazole clusters as secondary building units

Solvothermal reactions of manganese(II) chloride tetrahydrate with a bis-tetrazole ligand, 2,6-di(1H-tetrazol-5-yl)naphthalene (H(2)NDT), in N,N'-dimethylformamide (DMF)/MeOH mixed solvent at two slightly different temperatures, 75 and 100 °C, led to two different metal-organic frameworks (MOFs), [Mn(II)(3)O(HNDT)(2)(NDT)(DMF)(3)] (1) and [Mn(II)(5)O(2)(HNDT)(2)(NDT)(2)(DMF)(8)] (2), with different net topologies. Single-crystal X-ray diffraction studies reveal that 1 is constructed from an unprecedented trinuclear building block, [Mn(II)(3)O(CN(4))(6)], as a 6-connected trigonal prismatic secondary building unit (SBU) of topological D(3h) site symmetry, and that the ligand in the HNDT(-1)/NDT(2-) deprotonation states is a linker, where two tetrazole (CN(4)) groups of the ligand are connected via a rigid naphthyl group. The tetrazole groups in 1 adopt a 1,2-μ-bridging mode with the manganese(II) ions to form a μ(3)-oxo trinuclear SBU. The trigonalprismatic SBU in 1 is connected to six neighboring SBUs to form a three-dimensional MOF of acs net topology. 2 is constructed from an unprecedented pentanuclear building block, [Mn(II)(5)O(2)(CN(4))(8)], as an 8-connected tetragonal prismatic SBU of topological D(4h) site symmetry. The tetrazole groups in 2 adopt monodentate, 1,2-μ- and 2,3-μ-bridging bidentate and 1,2,3-μ-bridging tridentate binding modes with the manganese(II) centers to form a bis-μ(3)-oxo pentanuclear SBU of local C(2) site symmetry. The tetragonal prismatic SBU in 2 is connected to eight neighboring SBUs to form a 3-D MOF of bcu net topology.     

含氟二羧酸和含氮配体与过渡金属(Ⅱ)配合物的合成、表征及晶体结构

水热法合成了5个新的配位聚合物:[Cd(TFSA)(2,2’-bpy)2]n(1),[Mn(HFGA)(phen)2]n(2),[Co(TFSA)(bpp)2(H2O)2]n(3),[Zn(TFSA)(bpp)2(H2O)2]n(4)和[Cu(HFGA)(phen)]n(5)(TFSA=四氟丁二酸,HFGA=六氟戊二酸,2,2’-bpy=2,2’-联吡啶,phen=1,10-邻菲啰啉,bpp=1,3-二吡啶基丙烷),通过X射线单晶衍射确定了配合物的晶体结构.配合物1和2具有相似的1D链结构,四氟丁二酸和六氟戊二酸以两个单齿羧基氧原子分别配位于Cd2+和Mn2+离子,2,2’-联吡啶和1,10-邻菲啰啉分别螯合配位于Cd2+和Mn2+离子.配合物3和4具有相似的1D链结构,1,3-二吡啶基丙烷以两个端基氮原子桥联金属离子,四氟丁二酸和六氟戊二酸分别以单齿方式配位.配合物5是具有{4.82}拓扑的2D网结构,六氟丁二酸配体通过单齿/双齿-桥联模式连接Cu2+离子.5个配合物均通过分子间弱作用进一步构筑成3D超分子结构.     

Rod packings and metal-organic frameworks constructed from rod-shaped secondary building units

The principal structure possibilities for packing infinite rod-shaped building blocks are described. Some basic nets derived from linking simple rods (helices and ladders) are then enumerated. We demonstrate the usefulness of the concept of rod secondary building units in the design and synthesis of metal-organic frameworks (MOFs). Accordingly, we present the preparation, characterization, and crystal structures of 14 new MOFs (named MOF-69A-C and MOF-70-80) of 12 different structure types, belonging to rod packing motifs, and show how their structures are related to basic nets. The MOFs reported herein are of polytopic carboxylates and contain one of Zn, Pb, Co, Cd, Mn, or Tb. The inclusion properties of the most open members are presented as evidence that MOF structures with rod building blocks can indeed be designed to have permanent porosity and rigid architectures.     

Coexistence of magnetic and electric orderings in the metal-formate frameworks of [NH4][M(HCOO)3

A family of three-dimensional chiral metal-formate frameworks of [NH(4)][M(HCOO)(3)] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder-order transitions of NH(4)(+) cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8-30 K for the magnetic members, providing a new class of metal-organic frameworks showing the coexistence of magnetic and electric orderings.     

Magnetic ordering in three-dimensional metal-organic frameworks based on carboxylate bridged square-grid layers

Three isomorphous metal-organic frameworks of formula [M(ppdc)(H(2)O)(2)](n) [M = Mn(II), Fe(II), and Co(II)] were synthesized from sodium p-phenylenediacrylic (Na(2)ppdc). Crystallographic studies revealed that the compounds are layer-pillared 3D frameworks in which the square-grid M(II) layers with single carboxylate bridges are interlinked by long organic spacers with large interlayer separations of about 13 ?. Magnetic investigations indicated that they all display intralayer antiferromagnetic interactions through the carboxylate bridges in the unusual skew-skew coordination mode but the bulk behaviors are quite different. The Co(II) compound, like most compounds containing similar M-O-C-O-M layers, shows no 3D magnetic ordering down to 2 K, while the Mn(II) and Fe(II) compounds exhibit spin-canted ordering, behaving as a weak ferromagnet (T(C) = 3.8 K) and a metamagnet (T(N) = 3.8 K, H(c) = 650 Oe), respectively. Spin-canted ordering is still a rarity in this series of materials. Magnetostructural comparisons with analogous compounds indicate that the occurrence of spin-canted ordering can be related to the uncommon skew-skew and anti-anti coordination modes of carboxylate bridges, which induce stronger antiferromagnetic interactions than the common syn-anti mode.     

Chemoenzymatic synthesis of chiral 4,4'-bipyridyls and their metal-organic frameworks

The first enantiopure 4,4'-bipyridyls, , , and have been prepared in four or five steps via bacterial dioxygenase-catalysed cis-dihydroxylation of 4-chloroquinoline and C-C coupling; ligands and are found to be effective building blocks for the preparation of chiral metal-organic frameworks as demonstrated with the rational synthesis of two pillared-grid structures [Zn(2)(fumarate)(2)(L)], which exhibit interesting structural and dynamic aspects.     

3D metal-organic frameworks based on elongated tetracarboxylate building blocks for hydrogen storage

Two 3D metal-organic frameworks (MOFs) with a new biphenol-derived tetracarboxylate linker and Cu(II) and Zn(II) metal-connecting points were synthesized and characterized by single-crystal X-ray crystallographic studies. The two isostructural MOFs exhibit distorted PtS network topology and show markedly different framework stability. The porosity and hydrogen uptake of the frameworks were determined by gas adsorption experiments.     

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 New Cadmium Metal-organic Frameworks Based on a Mixed-donor Ligand

The self-assembly of a prominent mixed-donor ligand, 5-[4-(1H-tetrazolyl)phen]isophthalic acid(H₃TZPI), with a Cd²⁺ center generates two new metal-organic frameworks:[Cd(H₂TZPI)₂(H₂O)₂]_n(JUC-163) and[Cd₂(TZPI)(μ₃-OH)(H₂O)₂]·H₂O·DMF(JUC-164). The two complexes demonstrate different structures for the ligand’s different coordination modes and configurations. JUC-163 shows a 2D layer structure and further forms into a 3D supramolecular framework by noncovalent interactions(C-H…O, O-H…N and π…π interactions), whereas JUC-164 exhibits a fascinating 3D framework for the outstanding coordination modes and configurations of the ligand, which are fit for the complex structure. And also, the factor of different cadmium salts(chloride and nitrate) which are used in synthesis progress is worth to notice for the construction of the two distinct structures. The luminescent properties of these metal-organic frameworks were also investigated.     

Controllable preparation, network structures and properties of unusual metal-organic frameworks constructed from 4,4'-(hexafluoroisopropylidene)diphthalic acid and 4,4'-bipyridyl

Three novel 3D metal-organic frameworks of [Ni(2)(hfpdpt)(bpy)(2)(H(2)O)(2)](H(2)O)(8) (1), [Ni(3)(Hhfpdpt)(2)(bpy)(4)](H(2)O)(2) (2), and [Mn(2)(hfpdpt)(H(2)O)(2)] (3) have been synthesized by the hydrothermal reaction of Ni(II) or Mn(II) nitrate, 4,4'-(hexafluoroisopropylidene)diphthalic acid (H(4)hfpdpt), and 4,4'-bipyridyl (bpy). Complex 1 self-assembles into a 3D framework with unconventional 4-connected network topology, while 2 and 3 exhibit two kinds of unusual (4,8)-connected topological networks. Notably, in 1 and 2, the bpy coligand participates in the construction of their 3D frameworks, and the pH value also plays an important role to tune their space arrangements, while in 3, the bpy coligand is not involved in the final crystalline lattice. Furthermore, a detailed investigation on their magnetic and adsorptive properties is carried out.     

New metal-anion radical framework materials: Co(II) compounds showing ferromagnetic to antiferromagnetic phase transition at about 344 K, and Zn(II) compounds exhibiting terminal anion ligand induced direct white-light-emission

The preparation, X-ray crystallography, EPR, magnetic and luminescent investigation of new metal-anion radical framework materials based on a new anion radical ligand generated by in situ deprotonation of a stable zwitterionic radical are described herein. N,O,N-tripodal anion radical ligand (bipo(-)˙) links metal cations, giving rise to four isostructural one-dimensional metal-organic frameworks, [M(bipo(-)˙)(L)](n) [M = Zn, L = HCOO(-) (1), SCN(-) (1a), N(3)(-) (1b); M = Co, L = Br(-) (3)]. The tripodal bipo(-)˙ ligand and one co-ligand, 1,4-benzenedicarboxylate, coordinate to metals leading to two isostructural two-dimensional metal-organic frameworks, [M(bipo(-)˙)(BDC)(0.5)](n) [M = Zn (2) and Co (4)]. The two Co(II) compounds are the first examples that exhibit unusual ferromagnetic to antiferromagnetic phase transition with transition temperature over room temperature, which can be demonstrated by the cooling and warming measurements of susceptibility. Compound 4 also exhibits long-range magnetic ordering with the critical temperature at about 44 K proved by ac susceptibility measurements. The metal-radical frameworks exhibit distinctly different fluorescence emissions. Especially, the isomorphous one-dimensional Zn(II) compounds show interesting terminal anion ligand-induced photoluminescent color changes, including direct and invariable white-light-emission with terminal SCN(-) ligand.     

Synthesis, structural diversity and fluorescent characterisation of a series of d10 metal-organic frameworks (MOFs): reaction conditions, secondary ligand and metal effects

Along with our recent investigation on the flexible ligand of H(2)ADA (1,3-adamantanediacetic acid), a series of Zn(II) and Cd(II) metal-organic frameworks, namely, [Zn(3)(ADA)(3)(H(2)O)(2)](n)·5nH(2)O (1), [Zn(ADA)(4,4'-bipy)(0.5)](n) (2), [Zn(2)(ADA)(2)(bpa)](n) (3), [Zn(2)(ADA)(2)(bpa)](n) (4), [Zn(2)(ADA)(2)(bpp)](n) (5), [Cd(HADA)(2)((4,4'-bipy)](n) (6), [Cd(3)(ADA)(3)(bpa)(2)(CH(3)OH)(H(2)O)](n) (7), and [Cd(2)(ADA)(2)(bpp)(2)](n)·7nH(2)O (8) have been synthesized and structurally characterized (where 4,4'-bipy = 4,4'-dipyridine, bpa = 1,2-bis(4-pyridyl)ethane and bpp = 1,3-bis(4-pyridyl)propane). Due to various coordination modes and conformations of the flexible dicarboxylate ligand and the different pyridyl-containing coligands, these complexes exhibit structural and dimensional diversity. Complex 1 exhibits a three-dimensional (3D) framework containing one-dimensional (1D) Zn(II)-O-C-O-Zn(II) clusters. Complex 2 exhibits a 2D structure constructed by 1D double chains based on [Zn(2)ADA(2)] units and a 4,4'-bipy pillar. Complexes 3 and 4 possess isomorphic 2D layer structures, resulting from the different coordination modes of carboxylate group of ADA ligands. Complex 5 features a 2D 4(4) layer in which ADA ligands and Zn(II) atoms construct a 1D looped chain and the chains are further connected by bpp ligands. Complex 6 is composed of 1D zig-zag chains that are entangled through hydrogen-bonding interactions to generate a 2D network. Complex 7 is a rare (3,5)-connected network. Complex 8 possesses a 3D microporous framework with lots of water molecules encapsulated in the channels. The structural diversity of the complexes perhaps mainly results from using diverse secondary ligands and different metal centre ions, and means the assistant ligand and metal centre play important roles in the design and synthesis of target metal-organic frameworks. This finding revealed that ADA could be used as an effective bridging ligand to construct MOFs and change coordination modes and conformational geometries in these complexes. The thermogravimetric analyses, X-ray powder diffraction and solid-state luminescent properties of the complexes have also been investigated.