Inorganic Connectivity Research Articles

Lanthanide-Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation.

Implementation of lanthanide-organic frameworks (LOFs) as solid adsorbents has been frequently handicapped by their permanent porosity being difficult to establish owing to the remarkable flexibility and diversity of lanthanide ions in terms of coordination number and geometry. Construction of robust LOFs with permanent porosity for industrially important hydrocarbon separation will greatly expand their application potential. In this work, by distributing N and O donors into an m-terphenyl skeleton, we rationally synthesized a heterofunctional linker, and constructed a pair of isostructural LOFs. Due to the inclusion of a rarely observed three-dimensional metal-carboxylate backbone serving as a highly connected inorganic secondary building unit, their permanent porosities were successfully established by diverse gas isotherms. They can be applied as separating media not only for natural gas purification and removal of carbon dioxide from C2 hydrocarbons but also more importantly for single-step ethylene (C2H4) purification from a three-component C2Hn mixture during the adsorption process. The latter separation is very challenging and has been less reported in the literature. This work provides a unique example of LOFs featuring three-dimensional inorganic connectivity applied to multipurpose hydrocarbon separations.

Investigating the effect of positional isomerism on the assembly of zirconium phosphonates based on tritopic linkers.

We report on the use of a novel tritopic phosphonic linker, 2,4,6-tris[3-(phosphonomethyl)phenyl]-1,3,5-triazine, for the synthesis of a layered zirconium phosphonate, named UPG-2. Comparison with the structure of the permanently porous UPG-1, based on the related linker 2,4,6-tris[4-(phosphonomethyl)phenyl]-1,3,5-triazine, reveals that positional isomerism disrupts the porous architecture in UPG-2 by preventing the formation of infinitely extended chains connected through Zr-O-P-O-Zr bonds. The presence of free, acidic P-OH groups and an extended network of hydrogen bonds makes UPG-2 a good proton conductor, reaching values as high as 5.7 × 10-4 S cm-1.

Structural Transformation Pathways of Alkaline Earth Family Coordination Polymers Containing 3,3',5,5'-Biphenyl Tetracarboxylic Acid.

The understanding of crystal stepwise transformation is very important to enclose the "black box" in the preparation of crystal materials. In this work, different structural intermediates were isolated prior to the formation of the final alkali earth coordination polymers (CPs) during the preparation of three pairs of alkali earth CPs through solvothermal method and convenient oil-bath reactions. Single crystal X-ray diffraction analysis demonstrated the structural transformation from a 0 D to 1 D inorganic connectivity for the Ca-CPs and Sr-CPs, but a 1 D to 0 D inorganic connectivity for Ba-CPs, involving the breakage/formation of chemical bonds in the reaction solutions. Further analyses indicated that these two different structural transformation pathways are determined by the deprotonation of organic acid, competitive balance between the inorganic and organic connectivity, and the twist of the linker. FT-IR spectra, thermogravimetric and luminescence behaviors agree with their structural characteristics.

Influence of organic cation planarity on structural templating in hybrid metal-halides.

Controlling the connectivity and topology of solids is a versatile way to target desired physical properties. This is especially relevant in the realm of hybrid halide semiconductors, where the long-range connectivity of the inorganic substructural unit can lead to significant changes in optoelectronic properties such as photoluminescence, charge transport, and absorption. We present a new series of hybrid metal-halide semiconductors, (phenH2)BiI5·H2O, (2,2-bpyH2)BiI5, (BrbpyH)BiI4·H2O, (phenH2)2Pb3I10·2H2O, and (2,2-bpyH2)2Pb3I10 where (phenH2)2+ = 1,10-phenanthroline-1,10-diium, (2,2-bpyH2)2+ = 2,2'-bipyridine-1,1'-diium and (BrbpyH)+ = 6,6'-dibromo-2,2'-bipyridium. These compounds allow us to observe how the planarity of the cation, induced either through structural modification in the case of (phenH2)2+ or through non-covalent interactions in (BrbpyH)+, both relative to (2,2-bpyH2)2+, modifies the inorganic substructural unit. While the Pb2+ series of compounds show minimal changes in inorganic connectivity, we observe large differences in the Bi3+ series, ranging from 0-D dimers to corner- and edge-sharing 1-D chains of octahedra. We find that compounds containing (phenH2)2+ and (BrbpyH)+ pack more efficiently than those with (2,2-bpyH2)2+ due to their retention of planarity leading to greater inorganic connectivity. Electronic structure calculations and optical diffuse reflectance reveal that the band gaps of these compounds are influenced by the degree of inorganic connectivity and the inorganic substructural unit distances. These results show that the structure and planarity of organic cations can directly influence both the inorganic connectivity and the optical properties that could be tuned for certain optoelectronic applications.

Ca-, Sr-, and Ba-Coordination polymers based on anthranilic acid via mechanochemistry.

Ca-, Sr-, and Ba-Based coordination polymers (CPs) were prepared mechanochemically by milling metal-hydroxide samples with anthranilic acid (oABAH). {[Ca(oABA)2(H2O)3]}n (1) consists of one-dimensional polymeric chains that are further connected by a hydrogen-bonding network. {[Sr(oABA)2(H2O)2]·H2O}n (2) is a one-dimensional CP in which water molecules bridge Sr2+ ions and increase the dimensionality by building an extended network. {[Ba(oABA)2(H2O)]}n (3) crystallizes as a two-dimensional CP comprising one bridging water molecule. The cation radii influence the inorganic connectivity and dimensionality of the resulting crystal structures. The crystal structures were refined from powder X-ray diffraction data using the Rietveld method. The local coordination environments were studied via extended X-ray absorption fine structure (EXAFS) measurements. The compounds were further characterized using comprehensive analytical methods such as elemental analysis, thermal analysis, MAS NMR, imaging, and dynamic vapor sorption (DVS) measurements. Compounds 1, 2, and 3 exhibit small surface areas which decrease further after thermal annealing experiments. All compounds exhibit a phase transformation upon heating, which is only reversible in 3.

Frontier Orbital Engineering of Metal–Organic Frameworks with Extended Inorganic Connectivity: Porous Alkaline-Earth Oxides

The development of conductive metal-organic frameworks is challenging owing to poor electronic communication between metal clusters and the organic ligands that bridge them. One route to overcoming this bottleneck is to extend the inorganic dimensionality, while using the organic components to provide chemical functionality. Using density functional theory methods, we demonstrate how the properties of the alkaline-earth oxides SrO and BaO are transformed upon formation of porous solids with organic oxygen sources (acetate and trifluoroacetate). The electron affinity is significantly enhanced in the hybrid materials, while the ionization potential can be tuned over a large range with the polarity of the organic moiety. Furthermore, because of their high-vacuum fraction, these materials have dielectric properties suitable for low-κ applications.

Hydrothermal syntheses and characterization of two novel luminescent Cadmium(II) frameworks: From 1D infinite triple Cd-(trz)-Cd bridges to a rare I2O0 network with 2D Cd–Br–Cd inorganic connectivity

Using the 4-substituted-1,2,4-triazole derivate ligand 4-p-tolyl-1,2,4-triazole (L), two novel luminescent Cadmium(II) frameworks, namely {[Cd(μ2-L)3]·(NO3)2·L}n (1) and [Cd1.5(μ2-L)(μ2-Br)2(μ3-Br)]n (2) have been isolated under hydrothermal conditions. The structural analysis reveals that 1 presents a one-dimensional (1D) chain structural motif containing novel infinite triple Cd-(trz)-Cd bridges (triply trz-bridged M–M species). While 2 presents a rare I2O0 type framework, in which the infinite 2D Cd–Br–Cd inorganic connectivity with a 4-connected Kagome topology can be observed. The FT-IR, PXRD and thermal stabilities of 1–2 have investigated. The solid-state photo-luminescent spectra of organic ligand L and 1–2 also have been measured indicating strong emission bands.

Mixed-metal–organic frameworks (M′MOFs) from 1D to 3D based on the “organic” connectivity and the inorganic connectivity: syntheses, structures and magnetic properties

Based on the InOm notion (In = the dimensionality of the inorganic connectivity; Om = the dimensionality of the organic connectivity; n + m ≤ 3), we obtained ten transition/alkaline earth mixed-metal–organic frameworks (M′MOFs) from 1D to 3D through a “metalloligand” strategy at room temperature. Single-crystal X-ray diffraction analyses indicate that the resulting compounds possess the square plane [MII(pzdc)2]2− (M = Co, Ni or Cu) “organic” connectivity and the Ae–O–Ae (Ae = Ca, Sr or Ba) inorganic connectivity, which can be classified as I1O0 connectivity for complexes 1, 4, 7 and 9, I1O1 connectivity for complexes 2, 3, 5, 6 and 8 and I1O2 connectivity for complex 10. The [MII(pzdc)2]2− moieties acting as bis(tetradentate) polycarboxylate ligands show three types of coordination modes, namely μ4-(η2-O,O)2,(η1-O′)2, μ6-(η2-O,O)2,(η1-O′)2,(η1-O′)2 and μ10-(η2-O,O)2,(η2-O′,O′)2, (η1-O′)2,(η1-O′)2,(η1-N′)2. Additionally, the thermal stabilities of complexes 1–10 and magnetic properties of complexes 1, 2, 4, 5 and 10 have also been investigated.

A highly connected (5,5,18)-c trinodal MOF with a 3D diamondoid inorganic connectivity: tunable luminescence and white-light emission

A highly connected (5,5,18)-c trinodal MOF featuring a 3D diamondoid inorganic connectivity was synthesized. Tunable color and white light emission can be achieved by inclusion of Eu3+ into the framework.

Bi–Mn mixed metal organic oxide: A novel 3d-6p mixed metal coordination network

A new terminology of metal organic oxide (MOO) was given a definition as a type of coordination polymers which possess the feature of inorganic connectivity between metals and the direct bonded atoms and show 1D, 2D or 3D inorganic sub-networks. One such compound was shown as an example. A 3d-6p (Mn–Bi. Named MOOMnBi) mixed metals coordination network has been synthesized via hydrothermal method. The new compound with the molecular formula of [MnBi2O(1,3,5-BTC)2]n (1,3,5-BTC stands for benzene-1,3,5-tricarboxylate) was characterized via single crystal X-ray diffraction technique that revealed a very interesting 3-dimensional (3D) framework with Bi4O2(COO)12 clusters which are further connected to Mn(COO)6 fragments into a 2D MOO. The topology study indicates an unprecedented topological type with the net point group of {413.62}{413.68}{416.65}{418.610}{422.614}{43} corresponding to 3,6,7,7,8,9-c hexa-nodal net. MOOMnBi shows catalytic activity in the synthesis of (E)-α,β-unsaturated ketones.

Alkaline earth metal (Mg, Sr, Ba)-organic frameworks based on 2,2',6,6'-tetracarboxybiphenyl for proton conduction.

Three new alkaline earth metal based metal-organic frameworks (MOFs), namely M-BPTC (M = Mg, Sr, Ba), have been synthesized by using BPTC (2,2',6,6'-tetracarboxybiphenyl) as ligand under hydrothermal conditions. These MOFs exhibit interesting structural diversity, variable chemical and thermal stability, as well as proton conductivity. Mg-BPTC with the formula {[Mg(BPTC)0.5(H2O)3]·5H2O}n consists of BPTC(4-) extended metal layers, and novel highly ordered infinite tape-like structures of cyclic water octamers reside interlayer. Three-dimensional porous {[Sr2(BPTC)(H2O)6]·H2O}n (Sr-BPTC) features inorganic Sr-O chains (I(1)O(2)) and open hydrophilic channels where water heptamers and carboxyl oxygen atoms conspire to form H-bond networks, whereas 3D {[Ba6(BPTC)3(H2O)6]·11H2O}n (Ba-BPTC) shows Ba-O inorganic layer (I(2)O(1)) and 1D channels incorporating large water 14-mers and 18-mers. M-BPTC (M = Mg, Sr) species exhibit excellent water stability and proton conductivity due to their respective appropriate pathways for proton transporting. M-BPTC (M = Sr, Ba) structures are highly thermally stable due to the presence of the inorganic connectivity. The present results suggest that M-BPTC (M = Mg, Sr) are promising materials for proton conduction and provide insight into the hydrogen bonding motif.

A barium based coordination polymer for the activity assay of deoxyribonuclease I.

A new coordination polymer which shows an unusual 2D inorganic connectivity was constructed. This compound exhibits distinct fluorescence quenching ability to the dye-labeled single-stranded DNA probes with different lengths, based on which an analytical method was developed for the activity assay of deoxyribonuclease I.

An unusual chiral 3D inorganic connectivity featuring a {Pb₁₈} wheel: rapid and highly selective and sensitive sensing of Co(II).

A pair of enantiomorphic frameworks featuring rare chiral 3D inorganic connectivity and a {Pb18} wheel, has been obtained via spontaneous resolution. They exhibit rapid and highly selective and sensitive sensing of Co(2+) ions.

Hydrothermal Synthesis and Characterization of Two Novel Lead(II) Frameworks: From 1D Infinite Helical Pb–(O–C–O)–Pb Linkage to 3D Infinite Pb–X–Pb Network (X = O and Br)

AbstractAbstract. Two aliphatic dicarboxy1ic acid ligands, iminodiacetic acid (H2L1) and 3,3‐thiodipropionic acid (H2L2), were used to construct two novel lead(II) frameworks, namely, [Pb(μ4‐L1)Br]n (1) and [Pb3(μ9‐L2)(μ2‐Br)2Br2]n (2), under hydrothermal conditions. It has to be noted that for 1 the central PbII ions are bridged by L2– ligands resulting in infinite right‐ and left‐handed helical Pb–(O–C–O)–Pb linkage. Compound 2 represents a novel 3D hybrid luminescent lead(II) framework with I3O0 type connectivity. For 2 infinite 2D Pb–O–Pb inorganic layers and trinuclear Pb3Br4 clusters are inter‐linked forming a 3D inorganic connectivity. In 1 the five‐coordinate central PbII ions adopt a hemi‐directed coordination arrangement, whereas in 2 six‐coordinate Pb1, six‐coordinate Pb2, and four‐coordinate Pb3 atoms adopt hemi‐directed coordination arrangements. The variable lead(II) coordination environment and flexible coordination modes of carboxy1ic acid ligands such as H2L1 and H2L2 also reveal great potential for constructing novel inorganic‐organic hybrid materials. Furthermore TGA, FT‐IR, PXRD, elemental analysis, and photo‐luminescent properties of 1 and 2 were investigated.

Three-dimensional molecular-based magnet of octacyanometalate-based tungstate(V)-cobalt(II) bimetallic assembly with TC = 26 K

A three-dimensional (3D) octacyanotungstate(V)-based molecular based magnet containing Co(II) ions, {[CoII4(H2O)6(C2O4)][WV(CN)8]2·6H2O}n (1), has been synthesized in acidic solution and structurally characterized. X-ray determination indicates that in 1 each [W(CN)8]3− structural unit is linked by seven neighboring Co(II) ions forming 2D Co–W–CN inorganic connectivity layers. Further short conjugated oxalate bridges join these neighboring 2D layers ultimately forming the 3D framework. Magnetic investigation of complex 1 reveals that long-range ferromagnetic ordering occurs below the Curie temperature of 26K. The beautiful butterfly-shaped magnetic hysteresis loop at 10K between −70KOe and 70KOe exhibits a rather high coercive field (HC=3010Oe). The remnant magnetization Mr is equal to 3055cm3mol−1. To our best knowledge, complex 1 is the first example of 3D cyano-based magnets bridged by C2O42− anions.

Hydrothermal syntheses of a series of cluster-based micro-porous luminescent cadmium(ii) metal–organic frameworks with 4-amino-benzene-1,2,4-triazole: topological diversity, gas absorption and photo-luminescent characterization

In this work the multi-dentate 4-amino-benzene-1,2,4-triazole (L1) ligand is used. A series of novel cluster-based micro-porous luminescent cadmium(II) frameworks, namely [Cd3(μ3-L1)2(μ2-L1)2(μ2-Cl)2Cl4]n (1), {[Cd2(μ3-L1)2(μ2-Br)2Br2]·1.05H2O}n (2) and {[Cd2(μ2-L1)3(L1)2(μ2-I)2]·(CdI4)·1.5H2O}n (3) have been isolated under hydrothermal conditions. 1 presents a 4-connected (4,4) topology using trinuclear Cd(II) clusters as basic nodes. For 1, two bridging μ2-Cl− anions and two bridging μ3-L1 ligands connect three neighboring CdII ions forming trinuclear Cd3 clusters. Each Cd3 cluster links four neighboring Cd3 clusters forming a 2D (two-dimensional) neutral micro-porous framework. 1D rhombic channels with dimensions of 7.594(2) A × 21.250(6) A can be observed along the c-axis. 2 presents a rare I1O3 hybrid type micro-porous framework. In 2 these bridging μ3-L1 ligands link central CdII ions forming a 3D Cd–L1 organic connectivity. Two kinds of 1D Cd–Br–Cd inorganic connectivities further consolidate the 3D Cd–L1 organic connectivity, which ultimately forms a rare I1O3 type hybrid framework. 3 presents a novel 3D cluster-based micro-porous cation framework containing 1D channels, in which guest CdI42− anions and water molecules are located. Topological analysis indicates that 3 presents a novel 4-connected dmp topology using binuclear Cd2I2 clusters as basic nodes. PXRD, TGA and Gas absorption experiments for 1–3 have also been carried out. Solid state photo-luminescent spectra of 1–3 have been determined indicating strong emission bands. For 1 selective photo-luminescent quenching for NO2− anions can be observed. The result also reveals that L1 can adopt various different coordinated modes and flexible spatial distortion dihedral angles (between aromatic benzene and triazole rings), which has great potential in the construction of these novel cluster-based micro-porous coordination frameworks.

Synthesis and Characterization of a Novel Luminescent Silver(I)-Chromium(III) Heterometallic Hybrid Material With a Tripodal Ligand N-(Carbamoylmethyl) Iminodiacetato Acid (H2ADA)

Using the tripodal N-(carbamoylmethyl)iminodiacetato acid (H2ADA) ligand and corresponding Ag(I) and Cr(III) salts, a novel two-dimensional (2D) heterometallic Ag(I)-Cr(III) coordination polymer [AgCr(ADA)2]n (1) has been isolated. H2ADA are deprotonated into ADA2−, which adopts a novel asymmetrical η1, η1, η1, η2, μ5-pentadentate coordination mode to bridge neighboring seven-coordinated Ag(I) and five-coordinated Cr(III) ions forming a 2D inorganic-organic hybrid framework containing 2D Ag-O-Cr inorganic connectivity. The solid-state fluorescence spectrum of 1 was also investigated exhibiting the maximum emission peak at 609 nm while no fluorescence emission band can be observed for the free ligand. 1 also represents a luminescent heterometallic hybrid framework with scarcely reported pentacoordinated deprotonated H2ADA ligands. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Tuning the Dimensionality of Inorganic Connectivity in Barium Coordination Polymers via Biphenyl Carboxylic Acid Ligands

The synthesis and characterization of three barium coordination polymers with one-, two-, and three-dimensional (1-D, 2-D, 3-D) inorganic connectivity based on biphenyl carboxylic acid ligands are described. Employing biphenyl-3,3′,5,5′-tetracarboxylic acid (H4BTTC) as a ligand, [Ba2(BTTC)(H2O)2]n (1, space group = Pn21a, a = 7.059(1) Å, b = 12.432(2) Å, c = 19.090(3) Å), a coordination polymer with 1-D inorganic connectivity (I1O2), can be synthesized. The coordinated water is strongly coordinated and removed at 270 °C. By using 4,4′-biphenyldicarboxylic acid (H2BPDC), [Ba(BPDC)]n (2, space group = C2/m, a = 6.955(2) Å, b = 5.947(1) Å, c = 13.852 (4) Å, β = 92.399(4)°) a coordination polymer with 2-D inorganic connectivity (I2O1) is obtained. The connection of the Ba–O bonds in each layer is topologically similar to CaF2. Using biphenyl-3,5,5′-tricarboxylic acid (H3BPTC) as a ligand, [Ba3(BPTC)2(NMF)5⊃2NMF]n (3, space group = I4̅2d, a = 25.984(3) Å, c = 13.999(2) Å) (NMF = N-methyl formamide), a structurally porous coordination polymer with rare 3-D inorganic connectivity (I3O0) can be synthesized. Hence, barium as a metal is extremely malleable with respect to construction of coordination polymers of different inorganic dimensionalities. 2 with I2O1 connectivity demonstrates extraordinary thermal stability and maintains its crystallinity until decomposition at 590 °C. The luminescence behavior of 1, 2, and 3 at room temperature has been investigated and is predominantly intraligand based.

Syntheses, structure, and properties of a series of three-dimensional lanthanide-based hybrid frameworks

A novel family of lanthanide hybrid frameworks, {[Ln2(IDA)3]·(H2O)2}n (Ln=Nd (1), Eu (2), Tb (3), Dy(4); H2IDA=iminodiacetic acid), has been synthesized from the self-assembly of the lanthanide ions (Ln3+) with iminodiacetic acid under hydrothermal conditions and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Structural analyses revealed 1–4 have intricate frameworks with three-dimensional (3D) Ln–O–Ln inorganic connectivity, in which the IDA2- − ligands adopt the different μ(3- and μ(4- bridging forms. The 3D inorganic skeleton of the hybrid can be described as helices of corner-sharing LnN1O8 polyhedra connected by edge-sharing dinuclear Ln2N4O12 units, specified by the Schlafli symbol of 8·.8·.103 as a 82·.10-a (lig) topology. The structures also show intersected lanthanide oxide ring channels occupied by guest water molecules, based on which the reversible de-/rehydration occurs. Photoluminescence measurements indicate 2 and 3 are red and green emitters, respectively, in the solid state at room temperature. Besides, the magnetic properties of 1 have been studied.

An inorganic–organic composite framework with an unprecedented 3D heterometallic inorganic connectivity and white-light emission

The first example of an inorganic-organic composite framework with a 3D inorganic Cd-O-M (M = Cd, Rb) connectivity, featuring a unique {Cd(7)Rb}(n) helix and nanoscale {Cd(16)Rb(4)} and {Cd(18)Rb(2)} rings, has been constructed and structurally characterized. This compound exhibits white-light emission and a wavelength-dependent photochromic response.