Solvent Accessible Void Space Research Articles

Polymorphism from a 1:1 Ln:BTB reaction pot: Solvothermal versus sonochemical synthesis of Ln-MOFs

A 1:1 reaction pot of lanthanide(III):1,3,5-benzenetrisbenzoate (Ln(III):BTB) in a 2:1 mixture of DMF/H2O was subject to solvothermal and sonochemical conditions in order to form new Ln-BTB polymorphs. Solvothermal crystal growth is time dependent, yielding a new MOF structure Nd4(BTB)4(H2O)10•(H2O)7 (1) after 1–2 days and two new analogues of Ln(BTB)(H2O), Nd(BTB)(H2O) (2) and Sm(BTB)(H2O) (3) after 3.5 days. Sonochemical synthesis produced a pure phase of Ln(BTB)(H2O)2•(H2O)2(DMF)3 (4–7, Ln = Nd3+ (4), Eu3+ (5), Tb3+ (6), and Er3+ (7)). Compound 1 is a novel 3-D framework that consists of undulating one-dimensional lanthanide-carboxylate secondary building unit (SBU) chains connected by BTB linkers, which pack into a hxl topology with rhombohedral and hexagonal channels. The total solvent accessible void space is 4581.6 Å3 which constitutes 37 % of the of the total unit cell volume. Compounds 2 and 3 are three-dimensional microporous networks consisting of mutually parallel-perpendicular, infinite, undulating one-dimensional metal-carboxylate SBU chains interlinked by BTB ligands. Compounds 4–7 were previously reported from four different synthetic protocols and feature Ln2(COO)6(H2O)4 SBUs linked by BTB linkers into a two-dimensional (3,6-connected) kgd network, which assembles via hydrogen bonds into a three-dimensional supramolecular framework. Gas adsorption studies on compound 4 indicate microporous and mesoporous sites that contribute relatively high Langmuir and BET surface areas up to 1161 m2/g and 671 m2/g, respectively. Eu(BTB)(H2O)2•(H2O)2(DMF)3 (5) displays strong luminescence under UV excitation and is a highly sensitive and selective sensor for Fe3+ ions and nitroaromatic compounds. Sensing occurs via luminescence quenching due to competitive absorption of excitation energy between the BTB framework and the analyte molecules.

Coordination networks assembled from Co(NCS)2 and 4′-[4-(naphthalen-1-yl)phenyl]-3,2′:6′,3″-terpyridine: Role of lattice solvents

The preparation and characterization of 4′-[4-(naphthalen-1-yl)phenyl]-3,2′:6′,3″-terpyridine (1) are described. Reactions of 1 with Co(NCS)2 under conditions of crystal growth by layering using different solvent combinations produced crystals of [Co(1)2(NCS)2]n·2nCHCl3 and [Co(1)2(NCS)2]n·2nC6H5Me, each of which comprised a (4,4) net. The orientations of 1 with respect to the planar network defined by the Co atoms are significantly different in [Co(1)2(NCS)2]n·2nC6H5Me compared to [Co(1)2(NCS)2]n·2nCHCl3, and the toluene molecules in [Co(1)2(NCS)2]n·2nC6H5Me are involved in π-stacking interactions. The solvent-accessible void-space in the latter consists of a series of interlinked cavities in contrast to the open channels in [Co(1)2(NCS)2]n·2nCHCl3. Thermogravimetric analysis was used to investigate solvent loss and uptake in the two coordination networks. After solvent loss from [Co(1)2(NCS)2]n·2nCHCl3, CHCl3, CDCl3 or CH2Cl2 could be taken up by the lattice. In contrast, removal of toluene from [Co(1)2(NCS)2]n·2nC6H5Me was found to be irreversible.

Chiral Coordination Polymers of Mandelate and its Derivatives: Tuning Crystal Packing by Modulation of Hydrogen Bonding

Chiral coordination polymers constructed from mandelic acid have shown promise in enantioselective recognition and sensing, whereas its methoxy-protected derivative, α-methoxyphenyl acetic acid, is rarely used as a ligand in coordination polymers. In this study, mandelic acid, 3,5-difluoromandelic acid, and α-methoxyphenyl acetic acid were combined with divalent transition metals and bridging dipyridyl co-ligands to obtain a series of six 1D coordination polymers. The coordination polymers of mandelate and 3,5-difluoromandelate possessed densely packed structures stabilised by hydrogen bonding. In contrast, the use of (R)-α-methoxyphenyl acetic acid gave rise to zig-zag chains with significant solvent-accessible void space.

Intermolecular interactions and disorder in six isostructural celecoxib solvates.

Six isostructural crystalline solvates of the active pharmaceutical ingredient celecoxib {4-[5-(4-methylphenyl)-3-(trifluoromethyl)pyrazol-1-yl]benzenesulfonamide; C17H14F3N3O2S} are described, containing dimethylformamide (DMF, C3H7NO, 1), dimethylacetamide (DMA, C4H9NO, 2), N-methylpyrrolidin-2-one (NMP, C5H9NO, 3), tetramethylurea (TMU, C5H12N2O, 4), 1,3-dimethyl-3,4,5,6-tetrahydropyrimidin-2(1H)-one (DMPU, C6H12N2O, 5) or dimethyl sulfoxide (DMSO, C2H6OS, 6). The host celecoxib structure contains one-dimensional channel voids accommodating the solvent molecules, which accept hydrogen bonds from the NH2 groups of two celecoxib molecules. The solvent binding sites have local twofold rotation symmetry, which is consistent with the point symmetry of the solvent molecule in 4 and 5, but introduces orientational disorder for the solvent molecules in 1, 2, 3 and 6. Despite the isostructurality of 1-6, the unit-cell volume and solvent-accessible void space show significant variation. In particular, 4 and 5 show an enlarged and skewed unit cell, which can be attributed to a specific interaction between an N-CH3 group in the solvent molecule and the toluene group of celecoxib. Intermolecular interaction energies calculated using the PIXEL method show that the total interaction energy between the celecoxib and solvent molecules is broadly correlated with the molecular volume of the solvent, except in 6, where the increased polarity of the S=O bond leads to greater overall stabilization compared to the similarly-sized DMF molecule in 1. In the structures showing disorder, the most stable orientations of the solvent molecules make C-H...O contacts to the S=O groups of celecoxib.

Reversible and Vapochromic Chemisorption of Ammonia by a Copper(II) Coordination Polymer

The single crystal X-ray structure determination of {[Cu(tpt)(o-phthalate)]·31/3(C2H2Cl4)}n (tpt=2,4,6-tri-4-pyridyl-1,3,5-triazine, C2H2Cl4=1,1,2,2-tetrachloroethane=TCE) shows a 3D network in which CuII centres are linked by 3-connecting tpt ligands with the topology of a 12,3 net. CuII centres are further linked by o-phthalate dianions. The copper coordination geometry is square pyramidal, with o-phthalate oxygen donors trans to each other in the basal plane and the remaining positions taken by the pyridines of three linking tpt units. The solvent accessible void space is ~65%. The pale blue-green crystalline desolvate, obtained by heating to 200°C or washing the TCE solvate with acetone is formulated as [Cu(tpt)(o-phthalate)]n. Powder X-ray diffraction and electron paramagnetic resonance spectroscopy show that the crystal structure and the CuII geometry changes upon desolvation. The crystalline desolvated phase sorbs two equivalents of ammonia per copper ion. The adduct, mauve [Cu(tpt)(o-phthalate)(NH3)2]n, shows reasonable crystallinity and is stable up to ~150°C under ambient conditions before the reversible desorption (minimum 10 cycles) of the guest ammonia. The colour change and high desorption temperature, along with changes in g values, is suggestive of chemisorption in two steps with Cu–ammine bonding in the loaded phase.

1D and 3D coordination polymers based on the Cu3(μ3-OH)(μ-pz)3 and Cu(Hpz)3 SBUs connected by the flexible glutarate dianion

Different synthetic procedures lead to different coordination polymers (CPs) based either on the trinuclear triangular [Cu3(μ3-OH)(μ-pz)3]2+ or on the mononuclear [Cu(Hpz)3]2+ (Hpz=pyrazole) secondary building units (SBUs), bridged by the flexible glutarate (Glu) dianion. The mononuclear complex [Cu(HGlu)2(Hpz)4] was also obtained as byproduct. One of the CPs based on the trinuclear SBU displays a relevant porosity due to three intersecting channels, accounting for about 40% of the solvent accessible void space.

Commensurate CO2 Capture, and Shape Selectivity for HCCH over H2CCH2, in Zigzag Channels of a Robust Cu(I)(CN)(L) Metal-Organic Framework.

A novel copper(I) metal-organic framework (MOF), {[Cu(I)2(py-pzpypz)2(μ-CN)2]·MeCN}n (1·MeCN), with an unusual topology is shown to be robust, retaining crystallinity during desolvation to give 1, which has also been structurally characterized [py-pzpypz is 4-(4-pyridyl)-2,5-dipyrazylpyridine)]. Zigzag-shaped channels, which in 1·MeCN were occupied by disordered MeCN molecules, run along the c axis of 1, resulting in a significant solvent-accessible void space (9.6% of the unit cell volume). These tight zigzags, bordered by (Cu(I)CN)n chains, make 1 an ideal candidate for investigations into shape-based selectivity. MOF 1 shows a moderate enthalpy of adsorption for binding CO2 (-32 kJ mol(-1) at moderate loadings), which results in a good selectivity for CO2 over N2 of 4.8:1 under real-world operating conditions of a 15:85 CO2/N2 mixture at 1 bar. Furthermore, 1 was investigated for shape-based selectivity of small hydrocarbons, revealing preferential uptake of linear acetylene gas over ethylene and methane, partially due to kinetic trapping of the guests with larger kinetic diameters.

Highly porous hydrogen-bond networks from a triptycene-based catechol

Solvate crystals of 9,10-dimethyl-2,3,6,7,14,15-hexa(hydroxy)-triptycene (1) form a variety of 3D hydrogen-bonded topologies, including bcu, acs, bsn and an apparently new 7-connected net. Several of these networks contain 1D or 2D arrays of solvent-filled channels, amounting to up to 60% solvent-accessible void space.

Clathrate directed assembly of tetrapyridyl-tetraphenylethylene metal–organic frameworks

A highly microporous with rhomboid pores measuring ∼14 × 17 Å giving approximately 49% solvent accessible void space in which tetrachloroethylene molecules act as structure directing agents.

A three-dimensional anionic metal-dicyanamide network in poly[ethyltriphenylphosphonium [tri-μ2-dicyanamidato-cadmium(II)]

The title compound, (C20H20P)[Cd(C2N3)3], consists of ethyltriphenylphosphonium (EtPh3P(+)) cations filling voids in a three-dimensional anionic cadmium dicyanamide network. In the structure, each Cd(II) atom is connected to six neighbouring Cd(II) atoms through six separate dicyanamide ligands, forming cube-shaped cages. The three-dimensional anionic network encloses a solvent-accessible void space of 1851 Å(3), amounting to 69.3% of the unit-cell volume. Each cage accommodates only one EtPh3P(+) cation.

Synthesis and crystal structure of nickel coordination polymer with 2,8-di(pyridine-4-yl)dibenzothiophene

The title complex, {[Ni(DPDBT)(dctpa)(H2O)2] · (DMF)} n (1) was prepared under hydrothermal conditions based on two ligands, namely, 22,8-di(pyridin-4-yl)dibenzothiophene (DPDBT) and 4,4-(phenylazanediyl)dibenzoic acid (H2dctpa). π⋯π interaction plays an important role in the formation of supramolecular network structure of 1. There are a kind of channels in 1 with a cross section of approximately 8.4 × 8.4 × (excluding vander Waals radii). Complex 1 contains a solvent accessible void space of 14.7% of the total crystal volume.

Organosilicon linkers in metal organic frameworks: the tetrahedral tetrakis(4-tetrazolylphenyl)silane ligand

Formal substitution of the central carbon by silicon within the tetrahedral tetrakis(4-tetrazolylphenyl)methane linker in a copper-based MOF is shown to uniquely influence the structure of the resultant MOF, affecting the orientation of the metal-based nodes and leading to an increase in unit-cell volume and solvent accessible void space.

Hydrogen bond directed open-framework of bis(bipyridine-glycoluril) phosphatocobalt(III) with solvent accessible void space

The self-assembled secondary building unit [Co(BPG)2(PO4)]·2H2O (1) with peripheral urea fused tectons having inherent hydrogen bond acceptor (O atoms) and donor (N–H atoms) groups results in a three-dimensional open-framework architecture with approximately 35% of solvent-accessible void space.

A Three-Dimensional Open-Framework Indium Selenide: [C7H10N][In9Se14

An open-framework indium selenide, [C7H10N][In9Se14], has been prepared under solvothermal conditions in the presence of 3,5-dimethylpyridine and characterized by single-crystal X-ray diffraction, thermogravimetry, elemental analysis, Fourier tranform IR spectroscopy, and UV-vis diffuse reflectance. The crystal structure of [C7H10N][In9Se14] contains an unusual building unit, in which corner- and edge-linked InSe45- tetrahedra coexist. The presence of one-dimensional circular channels, of ca. 6 A diameter, results in approximately 25% of solvent-accessible void space.

Three-dimensional gallium sulphide open frameworks

The synthesis and crystal structure of four gallium sulphide open frameworks, built from supertetrahedral clusters, are described. The structures of [ C 4 NH 12 ] 6 [ Ga 10 S 18 ] (1) and [ C 4 NH 12 ] 12 [ Ga 20 S 35.5 ( S 3 ) 0.5 O ] (2) contain supertetrahedral T3 clusters, while in the isostructural compounds [ C 4 NH 12 ] 16 [ Ga 10 S 18 M 4 Ga 16 S 33 ] ( M = Co (3), Zn ( 4)), T3 and T4 clusters alternate. These materials exhibit three-dimensional frameworks, with topologies consisting of two interpenetrating diamond lattices, and contain over 50% of solvent accessible void space. UV–Vis diffuse reflectance measurements indicate that these compounds are semiconducting, with band gaps over the range 3.4–4.1 eV.

Unprecedented (3,4)-connected metal–organic frameworks (MOFs) with 3-fold interpenetration and considerable solvent-accessible void space

Via solvothermal synthesis, the self-assembly of CuCl(2), 1,3,5-benzenetricarboxylic acid, and N,N'-bis(4-pyridylformamide)-1,4-benzene in DMF generated a novel coordination polymer containing an unprecedented (3,4)-connected network; 3-fold interpenetration and considerable solvent-accessible cavities occupied by reversible guest water molecules were also observed.

Channel-containing structures generated from linear coordination polymer chains containing [formula omitted]-bidentate ligands and Cu–Cu dimetal units

Four new one-dimensional coordination polymers containing the dimetal cluster Cu 2(OAc) 4 have been synthesized by reacting Cu(OAc) 2 ⋅ H 2O with two different N , N ′ -bidentate ligands. Reaction of the flexible ligand, 1,2-bis(4-pyridyl)ethane ( L 1), with the copper starting material produced two, co-crystallizing coordination polymers: catena-Poly[Cu 2(OAc) 4( L 1)] ⋅ 2H 2O ( 1) and catena-Poly[Cu 2(OAc) 4( L 1)]. In the solid state, 1 (monoclinic, C2/c, a = 24.9471 ( 17 ) Å , b = 13.3539 ( 9 ) Å , c = 8.8050 ( 6 ) Å , β = 93.6480 ( 10 ) ° , V = 2927.4 ( 3 ) Å 3 , Z = 4 ) features linear chains which are organized into layers. These layers stack along the crystallographic c-axis forming small hexagonal channels occupied by the solvent of crystallization. Compound 2 (triclinic, P-1, a = 7.6263 ( 6 ) Å , b = 8.5283 ( 6 ) Å , c = 9.8633 ( 6 ) Å , α = 74.1070 ( 10 ) ° , β = 68.2160 ( 10 ) ° , γ = 74.0090 ( 10 ) ° , V = 561.96 ( 7 ) Å 3 , Z = 1 ) also features linear chains of the coordination polymer, but differs from 1 in that the chains are packed so as to leave no significant channels. Reaction of the rigid ligand, 1,4-bis(4-pyridyl)buta-1,3-diyne ( L 2), with the copper starting material also afforded two co-crystallizing coordination polymers: catena-Poly[Cu 2(OAc) 4( L 2)] ( 3) and catena-Poly[Cu 2(OAc) 4( L 2)] ⋅ solvents ( 4). 3 (monoclinic, P2 1/m, a = 9.8065 ( 9 ) Å , b = 12.3793 ( 11 ) Å , c = 9.9408 ( 9 ) Å , β = 107.6009 ( 17 ) ° , V = 1150.29 ( 18 ) Å 3 , Z = 2 ), like 2, features linear chains and contains no significant solvent accessible void space. 4 (monoclinic, C2/c, a = 28.9810 ( 16 ) Å , b = 12.9301 ( 7 ) Å , c = 8.6954 ( 5 ) Å , β = 98.8010 ( 10 ) ° , V = 3220.0 ( 3 ) Å 3 , Z = 4 ) also consists of linear chains of the coordination polymer. However, the overall topology of 4 is identical to that of 1, with the generated hexagonal channels containing crystallographically unidentifiable solvents of crystallization. Compounds 1 and 2 and compounds 3 and 4 are pairs of polymorphic coordination polymers neglecting the solvents of crystallization in 1 and 4. The compounds, which represent four new examples of coordination polymers containing dimetal units, have been characterized by IR, elemental analysis, and thermogravimetric analysis in addition to X-ray crystallography.