Solvent-accessible Void Research Articles

Structural Characteristics and DNA Groove Binding Abilities of Two Zinc-Based Isoreticular MOFs.

In this study, we have synthesized two zinc(II)-based metal-organic frameworks (MOFs) designated as [Zn(4-nvp)(bdc)] ⋅ (MeOH) (1) and [Zn2(4-nvp)2(bpdc)2] ⋅ (DMF) (2) [4-nvp=4-(1-naphthylvinyl) pyridine, H2bdc=1,4-benzendicarboxylic acid and H2bpdc=4,4'-biphenyldicarboxylic acid]. Single-crystal X-ray diffraction (SCXRD) of both compounds unveiled an interesting paddle-wheel [Zn2(O2C-C)4] secondary building block (SBB) composed of dinuclear Zn (II) centers and four dicarboxylate groups with a (4,4) square grid topology. These SBBs are interconnected giving rise to an infinite 2D layer architecture. Notably, the grid structure is composed of MeOH molecules in compound 1 and DMF molecules in compound 2, both of them arranged in a free lattice. In both compounds, 3D supramolecular architecture is ultimately formed through the stacking of 2D layers. Since the length of the bpdc ligand is higher than that of the bdc ligand, the solvent-accessible void volume is comparatively higher for compound 2. To corroborate all non-bonded interactions, Hirshfeld analysis was carried out for synthesized compounds. DNA binding application was extensively investigated through docking study. Results indicated that the synthesized compounds have strong affinities towards DNA via DNA groove binding. Henceforth, the synthesized compounds 1 and 2 would open the door for their potential applications as particular protein binders and bioactive substances.

Supramolecular assembled Keggin based porous material: Synthesis, crystal structure, electrochemical and spectroscopic properties

In this paper, a new supramolecular assembled Keggin polyoxometalate (POM) based organic-inorganic porous material (A; [HSiMo12O40].3[C10H11N4O2S].48H2O) containing the compound sulfadiazine (SZD) has been prepared and its molecular structure was determined. To characterize the hybrid compound (A), X-ray crystallography, MALDI-TOF, UV–Vis, photoluminescence and FTIR methods were used. The electrochemical properties of the Keggin POM, SZD and porous hybrid (A) compounds were investigated in the −1.8 – 1.8 V range and the redox processes at some potentials of the hybrid compound (A) are irreversible at 250 and 500 mV/s scan rates. Thermal stability properties of the hybrid compound (A) were investigated by the TGA/DTA instruments. The loss of the adsorbed water molecules on the hybrid compound (A) starts at 28 °C temperature. Crystal structure of the hybrid compound contains a Keggin type polyoxometalate [HSiMo12O40]3− and three monoprotonated sulfadiazinium (HSZD)+ cations. In the structure of the hybrid material, there are solvent accessible voids along a axis filled with water molecule.

Dual Structure of a Vanadyl-Based Molecular Qubit Containing a Bis(β-diketonato) Ligand.

We designed [VO(bdhb)] (1') as a new electronic qubit containing an oxovanadium(IV) ion (S = 1/2) embraced by a single bis(β-diketonato) ligand [H2bdhb = 1,3-bis(3,5-dioxo-1-hexyl)benzene]. The synthesis afforded three different crystal phases, all of which unexpectedly contain dimers with formula [(VO)2(bdhb)2] (1). A trigonal form (1h) with a honeycomb structure and 46% of solvent-accessible voids quantitatively transforms over time into a monoclinic solvatomorph 1m and minor amounts of a triclinic solventless phase (1a). In a static magnetic field, 1h and 1m have detectably slow magnetic relaxation at low temperatures through quantum tunneling and Raman mechanisms. Angle-resolved electron paramagnetic resonance (EPR) spectra on single crystals revealed signatures of low-dimensional magnetic behavior, which is solvatomorph-dependent, being the closest interdimer V···V separations (6.7-7.5 Å) much shorter than intramolecular V···V distances (11.9-12.1 Å). According to 1H diffusion ordered spectroscopy (DOSY) and EPR experiments, the complex adopts the desired monomeric structure in organic solution and its geometry was inferred from density functional theory (DFT) calculations. Spin relaxation measurements in a frozen toluene-d8/CD2Cl2 matrix yielded Tm values reaching 13 μs at 10 K, and coherent spin manipulations were demonstrated by Rabi nutation experiments at 70 K. The neutral quasi-macrocyclic structure, featuring nuclear spin-free donors and additional possibilities for chemical functionalization, makes 1' a new convenient spin-coherent building block in quantum technologies.

Gas sorption properties of a new Zn‐BTB metal–organic framework with permanent porosity

AbstractA new three‐dimensional (3D) Zn‐based metal–organic framework (Zn‐MOF) with 1,3,5‐benzenetribenzoate (BTB3−), [Zn4O(BTB)2(0.5H2O)4]·H2O·8DEF (1), has been prepared using the reaction between Zn(NO3)2·6H2O and a tritopic bridging ligand 1,3,5‐benzenetribenzoic acid (H3BTB) in the presence of a potentially ditopic bridging ligand 3,3′‐terphenyldicarboxylic acid (H2TPDC). Interestingly, TPDC2− ligand did not incorporate into the resulting Zn‐MOF, and the title compound was not formed in the absence of TPDC2− ligand during the synthesis. After the solvate molecules were removed, Zn‐MOF 1 exhibited a doubly interpenetrated 3D ant net with a large solvent accessible void. The powder x‐ray diffraction pattern of the evacuated 1 did not change significantly compared to that of the as‐prepared 1, thus indicating that 1 has permanent porosity. Gas sorption analyses were performed to investigate the sorption abilities of the evacuated 1 by using several different gases at suitable temperatures: N2, CO2, H2, and CH4.

Chemical conversion of CO2 into cyclic carbonates by two Metal–Organic frameworks

Two metal–organic frameworks (MOFs), DDCu and DDMn have been synthesized from a tetracarboxylate ligand by solvothermal method. DDCu contained paddlewheel- [Cu2(COO)4] clusters with axial sites occupied by water molecules and comprised of two types of cages: smaller spherical cages of diameter 9.3 Å and larger ellipsoidal cages of dimensions of 12.4 × 17.7 Å2. While DDMn having bimetallic Mn2(COO)4 clusters with 1D rhombus channels of window size 10.16 × 8.97 Å2. Both the MOFs have open framework structure with solvent accessible void volume 66.5 % and 64.1 % based on the PLATON calculations. The MOFs have been characterized by a series of methods like Single crystal XRD, powder XRD, FT-IR, TGA and N2 adsorption study. Brunauer−Emmett−Teller (BET) surface area of the activated MOFs were 360 and 290 m2/g, respectively. The loosely bound water molecules could be removed to produce unsaturated metal coordination sites that rendered exciting heterogeneous catalytic properties at the metal center of DDCu and DDMn in the fixation of CO2 through the cycloaddition of CO2 with various epoxide. Under ambient conditions (25 °C and 1 atm. CO2 pressure), both the catalyst showed appreciable yields (96 and 91 %) and selectivity (>99 %) for cyclic carbonate formations. Both the catalysts showed very good recycling properties (at least five times).

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.

Unravelling the Origin of Solvate Formation in the Anticancer Drug Trametinib: Insights from Crystal Structure Analysis and Computational Modeling

The discovery of new crystalline forms of large, flexible drug molecules is of significant interest to the pharmaceutical industry as a means of improving one or more physicochemical properties of the active pharmaceutical ingredient (API). Trametinib (TRMB) is an anticancer drug, for which no solid-state forms are yet reported. Here, we report the results of an extensive screen for cocrystals of TRMB in an effort to improve the poor aqueous solubility of this API. Contrary to expectations, this effort led to the discovery of only six isostructural solvates of TRMB, where the solvent molecules fill the voids of the crystal structure and are stabilized by various intermolecular interactions. Computational crystal structure prediction methods were used to rationalize the high propensity for solvent inclusion in TRMB as arising from the poor crystal packing in TRMB. All predicted polymorphs of TRMB within a relative lattice energy of 44 kJ mol–1 of the global minimum display solvent accessible voids ranging from 1.4 to 16.5% of the unit cell volume. The serendipitous discovery of solvates in experiments targeting cocrystals,strongly suggests that the well-established synthon approach for the discovery of cocrystals works relatively well for documented literature examples that use rigid coformers with minimal conformational flexibility. However, for large APIs such as TRMB, in-silico screening methods should be adopted to reduce the need for extensive experimental cocrystal screens as the ability to form a cocrystal for drug candidates relies on more than synthon complementarity.

Structure and Vibrational Spectra of Pyridine Solvated Solid Bis(Pyridine)silver(I) Perchlorate, [Agpy2ClO4]·0.5py

A hemipyridine solvate of bis(pyridine)silver(I) perchlorate, [Agpy2ClO4]·0.5py (compound 1) was prepared and characterized by single crystal X-ray analysis and vibrational spectroscopy (R and low-temperature Raman). Compound 1 was prepared via the trituration of [Agpy2ClO4] and 4[Agpy2ClO4]·[Agpy4]ClO4 (as the source of the solvate pyridine) in a mixed solvent of acetone:benzene =1:1 (v = v) at room temperature. The monoclinic crystals of compound 1 were found to be isomorphic with the analogous permanganate complex (a = 19.1093(16) Å, b = 7.7016(8) Å, c = 20.6915(19) Å, β = 105.515(7)°; space group: C2/c). Two [Agpy2]+ cations formed a dimeric unit [Agpy2ClO4]2, and each silver ion was connected to two ClO4− anions via oxygen atoms. The Ag∙∙∙Ag distance was 3.3873(5) Å, the perchlorate ions were coordinated to silver ions, and the Ag∙∙∙O distances were 2.840(2) Å and 2.8749(16) Å in the centrosymmetric rectangle of Ag-O-Ag-O. The stoichiometric ratio of the monomer [Agpy2ClO4] and the solvent pyridine was 1:0.5. The guest pyridine occupied 527.2 Å3, which was 18.0% of the volume of the unit cell. There was no additional residual solvent-accessible void in the crystal lattice. The solvate pyridine was connected via its a-CH to one of the O atoms of the perchlorate anion. Correlation analysis, as well as IR and low-temperature Raman studies, were performed to assign all perchlorate and pyridine vibrational modes. The solvate and coordinated pyridine bands in the IR and Raman spectra were not distinguishable. A perchlorate contribution via Ag-O coordination to low-frequency Raman bands was also assigned.

Crystal structure of an indium-salicyl-hydroximate complex cation: [In4(H2shi)8(H2O)6](NO3)4·8.57H2O.

The synthesis and crystal structure for the title compound, hexa-aqua-hexa-kis(μ-2-hy-droxy-benzene-carbo-hydrox-a-mato)bis-(2-hy-droxy-benzene-carbo-hydrox-a-m-ato)tetra-indium(III) tetra-nitrate 8.57-hydrate + unknown solvent, [In4(H2shi)8(H2O)6](NO3)4·8.57H2O·solvent, where H2shi- is salicylhydrox-imate (C7H5NO3), are reported. The complex cation of the structure, [In4(H2shi)8(H2O)6]4+, is a dimer with a step-like topology and possesses an inversion center that relates each [In2(H2shi)4(H2O)3]2+ side of the complex cation. Each InIII ion is seven-coordinate with a penta-gonal-bipyramidal geometry, and the salicyl-hydroximate ligands have a 1- charge as only the oxime oxygen of the ligand is deprotonated. Four inter-stitial nitrate anions maintain the charge balance of the compound. One of the nitrate anions (and its symmetry equivalent) is disordered over two different orientations with an occupancy ratio of 0.557 (7) to 0.443 (7). The inter-stitial solvent water mol-ecules show substantial disorder. Approximately 8.57 water mol-ecules per formula unit were refined as disordered and partially occupied, while a suitable model could not be devised for the other extensively disordered solvent mol-ecules (water and possibly methanol as this was the synthesis solvent). Thus, these latter solvent mol-ecules were instead treated with the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9-18.] as implemented in the program PLATON, and the procedure corrected for 151 electrons within solvent-accessible voids of 367 Å3.

Poly[bis-(μ2-N,N-di-methyl-formamide-κ2 O:O)bis-(μ4-thio-phene-2,5-di-carboxyl-ato-κ4 O:O':O'':O''')dicobalt(II)

The asymmetric unit of the title three-dimensional metal-organic hybrid compound, [Co2(C6H2O4S)2(C3H7NO)2] n , comprises two cobalt(II) cations, one residing on a twofold axis and the other on a centre of inversion, one thio-phene-2,5-di-carboxyl-ate (tdc2-) ligand and one coordinating di-methyl-formamide (DMF) solvent mol-ecule. Both of the cobalt(II) cations exhibit an octa-hedral coordination environment from the four carboxyl O atoms of the tdc2- anions in a μ 4-κ 1:κ 1:κ 1:κ 1 fashion and two O atoms from DMF. A pair of carboxyl O atoms and one DMF molecule connect the adjacent cobalt(II) cations into an infinite chain, leading to a rod-spacer framework with rhombus-window channels, yet no residual solvent-accessible voids are present because the coordinating DMF molecules are oriented into the potential channels.

Fluorine-Functionalized NbO-Type {Cu2}-Organic Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation.

The high catalytic activity of metal-organic frameworks (MOFs) can be realized by increasing their effective active sites, which prompts us to perform the functionalization on selected linkers by introducing a strong Lewis basic group of fluorine. Herein, the exquisite combination of paddle-wheel [Cu2(CO2)4(H2O)] clusters and meticulously designed fluorine-funtionalized tetratopic 2',3'-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid (F-H4ptta) engenders one peculiar nanocaged {Cu2}-organic framework of {[Cu2(F-ptta)(H2O)2]·5DMF·2H2O}n (NUC-54), which features two types of nanocaged voids (9.8 Å × 17.2 Å and 10.1 Å × 12.4 Å) shaped by 12 paddle-wheel [Cu2(COO)4H2O)2] secondary building units, leaving a calculated solvent-accessible void volume of 60.6%. Because of the introduction of plentifully Lewis base sites of fluorine groups, activated NUC-54a exhibits excellent catalytic performance on the cycloaddition reaction of CO2 with various epoxides under mild conditions. Moreover, to expand the catalytic scope, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile were performed using the heterogenous catalyst of NUC-54a. Also, NUC-54a features high recyclability and catalytic stability with excellent catalytic performance in subsequent catalytic tests. Therefore, this work not only puts forward a new solution for developing high-efficiency heterogeneous catalysts, but also enriches the functionalization strategies for nanoporous MOFs.

Versatility within (4,4) networks assembled from 1,4-bis(n-alkyloxy)-2,5-bis(3,2′:6′,3′'-terpyridin-4′-yl)benzene and [Cu(hfacac)2] (Hhfacac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione)

The reactions of 1,4-bis(n-alkyloxy)-2,5-bis(3,2′:6′,3′'-terpyridin-4′-yl)benzene ligands with methoxy (1), ethoxy (2), n-propoxy (3), n-butyloxy (4), n-pentyloxy (5), n-hexyloxy (6), n-heptyloxy (7) and n-octyloxy (8) substituents with [Cu(hfacac)2].H2O (Hhfacac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) under conditions of crystal growth by layering have been investigated using different combinations of solvents. The products have been structurally characterized and in all cases, Cu(II) is octahedrally sited in a trans-{Cu(hfacac)2(N)2} environment in which N is a pyridine donor in one of the outer rings of a 3,2′:6′,3′'-tpy unit. The coordination assemblies fall into four categories. The most populated class consists of (4,4) nets in which each bis(3,2′:6′,3′'-tpy) ligand 1 and 4–8 acts as a 4-connecting node and the Cu(II) centres lie within the plane defined by the nodes; changes in conformation of the 3,2′:6′,3′'-tpy units do not affect the assembly of the (4,4) network. One of two assemblies isolated with ligand 2 is also a (4,4) net, but powder X-ray diffraction (PXRD) data indicate that this is not representative of the bulk material. [Cu2(hfacac)4(3)]n.5.5nC6H5Cl exhibits a unique structure consisting of a (4,4) net with the Cu(II) centres lying above and below the plane of the net. A third class of assembly was found for [Cu3(hfacac)6(5)2]n and comprises a (4,4) net in which half of the ligands are 4-connecting nodes and half coordinate through two pyridine rings and are therefore linkers; the efficient packing in this structure leaves no solvent-accessible voids. A 1D-coordination polymer in which all the bis(3,2′:6′,3′'-tpy) ligands are 2-connecting linkers was observed for [Cu2(hfacac)4(2)2]n.1.5nCHCl3.4nMeOH and PXRD data confirm that the structure is representative of the bulk material. Structural studies have been complemented by thermogravimetic analyses of selected compounds.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Coordination chemistry of polynitriles. Part 9. Decacyanoferrocene revisited: crystal and molecular structure of cis-[{C5(CN)5}2(MeCN)4Fe

The reaction of Ag[C5(CN)5] with anhydrous FeCl2 in acetonitrile leads to colourless crystals of tetrakis(acetonitrile-κN)bis(pentacyanocyclopentadienido-κN)iron(II) acetonitrile 1.8-solvate, [Fe(C10N5)2(CH3CN)4]·1.8CH3CN or cis-[{C5(CN)5}2(MeCN)4Fe]·1.8MeCN. The compound crystallizes in the triclinic space group P-1 as monomers, which exhibit weak C-H...N and π-π interactions. The crystals contain ca 20% solvent-accessible voids, which are nearly completely filled by two MeCN molecules.

Two-Step Spin Crossover in Hofmann-Type Coordination Polymers [Fe(2-phenylpyrazine)2{M(CN)2}2] (M = Ag, Au).

Two 2D Hofmann-type complexes of the composition [Fe(Phpz)2{M(CN)2}2] (where Phpz = 2-phenylpyrazine; M = Ag, Au) have been synthesized, and their spin-crossover (SCO) behavior has been thoroughly characterized. Single-crystal X-ray analysis reveals that these complexes contain a crystallographically unique Fe(II) center surrounded by two axial Phpz ligands and four equatorial cyanide [M(CN)2]- bridges. It is shown that, using of a ligand with two aromatic rings, an advanced system of weak supramolecular interactions (metal-metal, C-H···M, and π···π stacking contacts) is realized. This ensures additional stabilization of the structures and the absence of solvent-accessible voids due to dense packing. Both complexes are characterized by a highly reproducible two-step SCO behavior, as revealed by different techniques (superconducting quantum interference device magnetometry, optical microscopy, etc.). Research shows the exceptional role of the presence of various supramolecular interactions in the structure and the influence of the bulky substituent in the ligand on SCO behavior. Moreover, the perspective of substituted pyrazines for the design of new switchable materials is supported by this work.

Steric Repulsion Induced Conformational Switch in Supramolecular Structures.

Inspired by the rigidified architecture of ‘picket‐fence’ systems, we propose a strategy utilizing strain to impose intramolecular tension in already peripherally overcrowded structures leading to selective atropisomeric conversion. Employing this approach, tuneable shape‐persistent porphyrin conformations were acquired exhibiting distinctive supramolecular nanostructures based on the orientation of the peripheral groups. The intrinsic assemblies driven by non‐covalent bonding interactions form supramolecular polymers while encapsulating small molecules in parallel channels or solvent‐accessible voids. The developed molecular strain engineering methodologies combined with synthetic approaches have allowed the introduction of the pivalate units creating a highly strained molecular skeleton. Changes in the absorption spectrum indicated the presence of severe steric repulsions between the peripheral groups which were confirmed by single crystal X‐ray analysis. To release the steric strain introduced by the peripheral units, thermal equilibration strategies were used to selectively convert the most abundant atropisomer to the desirable minor one.

Two Zn(II)-organic frameworks: catalytic Knoevenagel condensation and treatment activity on spine surgery incision infection via inhibiting Staphylococcus aureus biofilms formation

By utilizing the mixed-ligand method, two novel metal-organic frameworks (MOFs) based on Zn(II) ions as nodes with the chemical formulae of {[Zn2.5(abta)(trz)2(H2O)]·3H2O}n (1, Htrz = 1H-1,2,4-triazole) and [Zn3(abta)2(bibb)2]n (2, bibb = 1,4-bis(benzimidazol-1-yl)-2-butene) were produced via Zn(NO3)2·6H2O reacting with the 1-aminobenzene-3,4,5-tricarboxylic acid (H3abta) in the existence of distinct nitrogen-donor co-ligands. The different N-donor ligands result in their distinct framework structures, and the compound 1 with higher solvent accessible void and large window size shows highly heterogeneous catalytic activities for Knoevenagel condensation. The treatment of Staphylococcus aureus biofilms formation during spine surgery incision infection and the related mechanism was explored at the same time. First of all, the S. aureus bacterial numbers in the infectious site was measured under compound 1 or 2 treatment. In addition to this, the relative expression levels of the genes related with S. aureus biofilms was determined with real time RT-PCR.

Synthesis and structure of 4-{[(E)-(7-meth-oxy-1,3-benzodioxol-5-yl)methyl-idene]amino}-1,5-dimethyl-2-phenyl-2,3-di-hydro-1H-pyrazol-3-one.

In the title compound, C20H19N3O4, the dihedral angles between the central pyrazole ring and the pendant phenyl and substituted benzene rings are 50.95 (8) and 3.25 (12)°, respectively, and an intra-molecular C-H⋯O link generates an S(6) ring. The benzodioxolyl ring adopts a shallow envelope conformation with the methyl-ene C atom as the flap. In the crystal, the mol-ecules are linked by non-classical C-H⋯O inter-actions, which generate a three-dimensional network. Solvent-accessible voids run down the c-axis direction and the residual electron density in these voids was modelled during the refinement process using the SQUEEZE algorithm [Spek (2015 ▸). Acta Cryst. C71, 9-18] within the structural checking program PLATON.

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.

Role of supramolecular interactions in crystal packing of Strandberg-type cluster-based hybrid solids

Two new Strandberg-type cluster-based phosphomolybdates {H-2a3mp}5[{PO3(OH)}{PO4}Mo5O15], 1 and {H-2a4mp}5[{PO3(OH)}{PO4}Mo5O15]·6H2O, 2 have been crystallized via solvent evaporation technique using 2-amino-3-methylpyridine (2a3mp) and 2-amino-4-methylpyridine (2a4mp) respectively. The solids were characterized using single-crystal X-ray diffraction, powder X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and cyclic voltammetry. The solid 1 crystallized in monoclinic system with space group P21/c, a = 8.394(1), b = 27.398(6), c = 21.521(4) A, β = 97.68(3)°, Z = 4. The solid 2 crystallized in triclinic system with space group P-1, a = 11.728(1), b = 14.234(1), c = 19.589(1) A, α = 68.906(3), β = 89.454(3), γ = 66.559(3)°, Z = 2. The solids 1 and 2 formed a supramolecular framework stabilized by hydrogen bonding interaction between cluster anions and organic moieties. CH…π interactions between the organic moieties reinforced the crystal packing in 1 and 2. While crystal packing effects resulted in the formation of solvent-accessible voids in 1; aggregation of lattice water molecules in 2 facilitated the formation of pentameric water cluster. In addition, electrochemical behavior of 1 and 2 has also been investigated. Two new Strandberg-type cluster based phosphomolybdates, 1 and 2 have been crystallized via solvent evaporation technique using 2-amino-3-methylpyridine and 2-amino-4-methylpyridine. Detailed structural analysis revealed the role of supramolecular interactions in the crystal packing of these solids. In addition, electrochemical behavior of 1 and 2 has also been investigated.