Flexible Dicarboxylate Research Articles

Polyoxometalate-Dicarboxylate Hybrid Dimers with {SiW10Cr2} Nodes: Syntheses, Structures, and Mass Spectrometric Characterization.

The current study describes a new family of hybrid dimers constructed from secondary building blocks based on a dichromium-substituted silicodecatungstate, {SiW10Cr2}, and flexible dicarboxylate ligands of varied lengths. All five polyoxometalate-organic hybrid compounds exhibit an entropically favored, cyclic dimer motif that contains just two {SiW10Cr2} clusters─the minimum to form a closed loop, linked by two aliphatic dicarboxylates, as revealed by single-crystal X-ray diffraction. Due to the kinetic inertness of such Cr3+-based hybrid dimers, ESI-MS has become a particularly useful technique for the characterization of these paramagnetic, NMR-unfriendly systems.

New polynuclear compounds based on N-methyliminodipropionic acid: Solution studies, synthesis and X-ray crystal structures

Six new polynuclear coordination compounds based on 3d transition metal ions (Cu(II), Ni(II)) and Zn(II) with the flexible dicarboxylate compound N-methyliminodipropionic acid (H2midp) were prepared and characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. Four of these compounds are 1D coordination polymers, namely [Cu(midp)(H2O)] (1), [Cu3(midp)2(H2O)4](NO3)2·6H2O (2) [Cu3(midp)2(H2O)4](CF3SO3)2·4H2O (3) and [NaZn(Hmidp)2](CF3SO3) (6). The structural analysis revealed that the chain structure of 1 is composed of [Cu(midp)(H2O)] units connected by the free carboxylato oxygen atom of neighbor units, in an alternate fashion. In 2 and 3, on the other hand, there are two [Cu(midp)H2O] units, connected by a central Cu(II) ion coordinating again to the free oxygen atom of the carboxylato groups. The Zn(II) compound is heteronuclear and the complex adopts a 1D cationic polymeric structure with zinc and sodium ions connected by two Hmidp– anions. The two other compounds are dinuclear, [Cu2(Hmidp)2(μ-H2O)2(H2O)2](CF3SO3)2·6H2O (4) and ([Ni2(midp)2(H2O)4] (5). Additionally, a Co(II) and a Cu(II) coordination compound were obtained with the same ligand and characterized by IR spectroscopy, thermal analysis and elemental analysis including metal quantification. For the copper compound the formula [Cu(Hmidp)](ClO4)·3H2O (7) is proposed while for the Co(II) compound (8) the proposed formula is [Co(midp)(H2O)2]. Solution studies of the ligand–M(II) systems (M(II) = Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) were also carried out in order to help the selection of the best synthetic conditions and also to complement the structural knowledge in the exploration of the potential formation of coordination polymers in these systems.

Flexible Piezoelectric Nanogenerators Based on One-Dimensional Neutral Coordination Network Composites

Metal–organic coordination polymers are modular systems whose structures can be modified in numerous ways to introduce and influence non-linear optical and electrical properties. However, their full potential as piezoelectric nanogenerators for self-powered electronics is yet to be uncovered. Here, we report a Zn(II)-based ferroelectric one-dimensional coordination network {[Zn(L1)(bpy)]·(H2O)1.5}∞ (1) derived from a flexible dicarboxylate ligand [PhPO(NH-(C6H4COOH))2] (L1H2) and 2,2′-bipyridine as a co-ligand. The origin of polarization in 1, despite its neutral structure, is due to the polyhedral distortions around the Zn(II) center as revealed by ab initio calculations. The presence of polarizable domains was visualized by piezoresponse force microscopy (PFM) experiments. Also, from the PFM studies, a sizable converse piezoelectric coefficient (d33) value of 19.4 pm/V was noticed for 1, which is unprecedentedly high for the class of neutral-network coordination polymers. Furthermore, flexible composite devices comprising a thermoplastic polyurethane (TPU) polymer with different weight percentages (wt %) of 1 were prepared and examined for application as piezoelectric nanogenerators. Notably, the champion device of this series (poled 5 wt % 1-TPU composite) exhibits a highest open-circuit voltage of 5.6 V and power density output of 14.6 μW/cm2.

Highlighting Recent Crystalline Engineering Aspects of Luminescent Coordination Polymers Based on F-Elements and Ditopic Aliphatic Ligands.

Three principal factors may influence the final structure of coordination polymers (CPs): (i) the nature of the ligand, (ii) the type and coordination number of the metal center, and (iii) the reaction conditions. Further, flexible carboxylate aliphatic ligands have been widely employed as building blocks for designing and synthesizing CPs, resulting in a diverse array of materials with exciting architectures, porosities, dimensionalities, and topologies as well as an increasing number of properties and applications. These ligands show different structural features, such as torsion angles, carbon backbone number, and coordination modes, which affect the desired products and so enable the generation of polymorphs or crystalline phases. Additionally, due to their large coordination numbers, using 4f and 5f metals as coordination centers combined with aliphatic ligands increases the possibility of obtaining different crystal phases. Additionally, by varying the synthetic conditions, we may control the production of a specific solid phase by understanding the thermodynamic and kinetic factors that influence the self-assembly process. This revision highlights the relationship between the structural variety of CPs based on flexible carboxylate aliphatic ligands and f-elements (lanthanide and actinides) and their outstanding luminescent properties such as solid-state emissions, sensing, and photocatalysis. In this sense, we present a structural analysis of the CPs reported with the oxalate ligand, as the one rigid ligand of the family, and other flexible dicarboxylate linkers with –CH2– spacers. Additionally, the nature of the luminescence properties of the 4f or 5f-CPs is analyzed, and finally, we present a novel set of CPs using a glutarate-derived ligand and samarium, with the formula [2,2′-bipyH][Sm(HFG)2 (2,2′-bipy) (H2O)2]•(2,2′-bipy) (α-Sm) and [2,2′-bipyH][Sm(HFG)2 (2,2′-bipy) (H2O)2] (β-Sm).

From a Well-Defined Organozinc Precursor to Diverse Luminescent Coordination Polymers Based on Zn(II)-Quinolinate Building Units Interconnected by Mixed Ligand Systems.

Introduction of photoactive building blocks into mixed-ligand coordination polymers appears to be a promising way to produce new advanced luminescent materials. However, rational design and self-assembly of the multi-component supramolecular systems is challenging from both a conceptual and synthetic perspective. Here, we report exploratory studies that investigate the potential of [Zn(q)2]2[tBuZn(OH)]2 complex (q = deprotonated 8-hydroxyquinoline) as an organozinc precursor as well as a mixed-ligand synthetic strategy for the preparation of new luminescent coordination polymers (CPs). As a result we present three new 2D mixed-ligand Zn(II)-quinolinate coordination polymers which are based on various zinc quinolinate secondary building units interconnected by two different organic linker types, i.e., deprotonated 4,4′-oxybisbenzoic acid (H2obc) as a flexible dicarboxylate linker and/or selected bipyridines (bipy). Remarkably, using the title organozinc precursors in a combination with H2obc and 4,4′-bipyridine, a novel molecular zinc quinolinate building unit, [Zn4(q)6(bipy)2(obc)2], was obtained which self-assembled into a chain-type hydrogen-bonded network. The application of the organometallic precursor allowed for its direct reaction with the selected ligands at ambient temperature, avoiding the use of both solvothermal conditions and additional base reagents. In turn, the reaction involving Zn(NO3)2, as a classical inorganic precursor, in a combination with H2obc and bipy led to a novel 1D coordination polymer [Zn2(q)2(NO3)2(bipy)]. While the presence of H2obc was essential for the formation of this coordination polymer, this ditopic linker was not incorporated into the isolated product, which indicates its templating behavior. The reported compounds were characterized by single-crystal and powder X-ray diffraction, elemental analysis as well as UV-Vis and photoluminescence spectroscopy.

A novel 3D Pb(II) coordination polymer from a flexible dicarboxylate ligand which reversibly absorbs water

The dicarboxylic flexible ligand 4-((2-carboxyethyl)amino)benzoic acid (LH3) has been synthesized and its reaction with Pb(NO3)2 lead to the formation of a 3D coordination polymer formulated as {[Pb(LH)(H2O)]⋅H2O}n (1) which presents a very interesting structure with an sra underlying topology. Thermal stability studies combined with X-ray powder diffraction suggest that the molecular material displays soft crystalline properties; upon heating it loses its water content changing its structure, while upon rehydration under a variety of conditions the original structure is obtained.

Structural and Thermal Investigations of Co(II) and Ni(II) Coordination Polymers Based on biphenyl-4,4'-dioxydiacetate Linker.

Two coordination polymers, [Co(µ4-L)(H2O)2]n (1) and [Ni(µ-L)(H2O)4]n (2), were solvothermally assembled from the corresponding metal(II) chlorides and biphenyl-4,4-dioxydiacetic acid (H2L) as a flexible dicarboxylate linker. The cobalt(II) compound 1 featured a layer-pillared 3D metal-organic network with a cds topology, while the nickel(II) derivative 2 represented a linear chain 1D coordination polymer with a 2C1 topology. The µ4− and µ-L2− linkers exhibited different denticity and coordination modes in the synthesized compounds, thus contributing to their structural diversity. The dimensionality of 1 and 2 had an influence on their thermal stability and decomposition processes, which were investigated in detail by TG-DSC and TG-FTIR methods. Thermal decomposition products of coordination polymers were also analyzed by PXRD, confirming the formation of Co3O4/CoO and NiO as final materials. The obtained compounds broaden a family of coordination polymers assembled from flexible dicarboxylate linkers.

Zn(II)-MOF with flexible dicarboxylate ligand with different N-donor linkage as photocatalyst for aromatic dye degradation

A new Zn(II)-based metal-organic framework (MOF) with formula [Zn2(NH2-BDC)2(H2O)] (1) (NH2-H2BDC = 2-aminoterephthalic acid), has been synthesized solvothermally and characterized. The single crystal X-ray diffraction indicated that 1 possess a 3D framework with a (44·62)2(43) topology. Also, the MOF exhibit efficient photocatalytic performance to photodegrade methyl violet (MV) under UV light. In presence of 1, 67.31% degradation of MV after 40 min has been observed. The intermediate as well as final degradation products of MV have been identified using LC–MS and the plausible photodegradation pathways of dye are discussed. In addition, the plausible photocatalytic mechanism been explained with the help of theoretical calculations using density of states.

Photocatalytic organic dye by two new coordination polymers with flexible dicarboxylate and different N-donor linkage

Two new Zn(II) coordination polymers (CPs) with [Zn(L)(2,2′-bipy)] (1) and [Zn(L)(bbi)0.5] (2) (H2L = 3,3′-(1,2-phenylenebis(methyleneoxy)) dibenzoic acid, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), 2,2,’-bipy = 2,2,’-bipyridine), have been solvothermally prepared. They exhibited 2D layer and 1D helical networks through the connectivity of Zn atoms and phenolic-oxygen containing branches of the flexible linkages. The N-donor ligand play a distinct effect in the formation of these mortifies. Both of them showed efficient photocatalytic performances to degrade methyl violet (MV) under UV irradiation. The percentage degradation of MV are 64.55% in presence of CP 1 while it is 78.54% with 2 as photocatalyst after 100 min of UV irradiation. The final degradation products were detected using LC–MS and the possible disassemble pathways for the degradation of dyes were discussed. The plausible photocatalytic mechanism through which both CPs displayed photocatalysis of MV have been explained using theoretical calculations.

1D Zn(II) Coordination Polymers as Effective Heterogeneous Catalysts in Microwave-Assisted Single-Pot Deacetalization-Knoevenagel Tandem Reactions in Solvent-Free Conditions

The new 1D CPs [Zn(L1)(H2O)4]n.nH2O (1) and [Zn(L2)(H2O)2]n (2) [L1 = 1,1′-(ethane-1,2-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid); L2 = 1,1′-(propane-1,3-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid)] were prepared from flexible dicarboxylate pro-ligands (H2L1 and H2L2). Both CPs 1 and 2 were characterized by elemental, FTIR, and powder X-ray diffraction analysis. Their geometry and the structural features were unveiled by single-crystal X-ray diffraction analysis. The underlying topology of the CPs was illustrated by the topological analysis of the H-bonded structure of CP 1, which revealed a 3,4,6-connected trinodal net. On the other hand, topological analysis on the hydrogen-bonded network of CP 2 showed a 2,3,3,4,6,7-connected hexanodal net. The thermal stability of the CPs was investigated by thermogravimetric analysis. CPs 1 and 2 act as heterogeneous catalysts in one-pot tandem deacetalization–Knoevenagel condensation reactions under environmentally mild conditions. CPs 1 exhibits a yield of ca. 91% in a microwave-assisted solvent-free medium, whereas a slightly lower yield was obtained for CP 2 (87%) under the same experimental protocol. The recyclability of catalyst 1 was also assessed. To our knowledge, these are the first Zn(II)-based CPs to be applied as heterogeneous catalysts for the above tandem reactions under environmentally friendly conditions.

Synthesis and characterization of two water stable coordination polymers with better photocatalytic property towards the organic pollutant in waste water

Two new Cu(II)/Co(II) coordination polymer (CPs) namely, [Co2(H2O)2(L)2(2,2′-bipy)2·H2O] (1) and [Cu2(L)2(bbi)] (2) (H2L=3,3′-(1,2-phenylenebis(methyleneoxy)) dibenzoic acid, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), 2,2,’-bipy=2,2,’-bipyridine), have been designed and synthesized. 1 has 1D helical structure built by the connectivity of Co atoms and phenolic-oxygen containing branches of the flexible dicarboxylate linkages, which was further form a 2D supramolecular sheet through the strong π···π stacking interactions and H-bonded interactions. 2 exhibits 2D layer constructed by the double [Cu4L2] chains and anti-conformational bbi ligands. The current results illustrated that the N-donor ligand may play a distinct effect in the formation of these mortifies. The photocatalytic performances to degrade methyl violet (MV) and Rhodamine B (Rh B) under UV irradiation were studied.

Temperature dependence of desolvation effects in hydrogen-bonded spin crossover complexes.

The synthesis, crystal structure and (photo)magnetic properties of the anhydrous spin crossover salt of formula [Fe(bpp)2](C6H8O4) (1) (bpp = 2,6-bis(pyrazol-3-yl)pyridine; C6H8O4 = adipate dianion), obtained by desolvation at 400 K of the original tetrahydrate in a single-crystal-to-single-crystal (SC-SC) transformation, are reported. This work offers a comparison between this compound and the previously reported hydrated material ([Fe(bpp)2](C6H8O4)·4H2O, 1·4H2O), highlighting the significance of the thermal conditions used in the dehydration-rehydration processes. In both compounds, a hydrogen-bonded network between iron(ii) complexes and adipate anions is observed. The original tetrahydrate (1·4H2O) is low-spin and desolvation at 450 K triggers a low-spin (LS) to high-spin (HS) transition to an amorphous phase that remains stable over the whole temperature range of study. Surprisingly, the dehydrated compound at 400 K (1) keeps the crystallinity, undergoes a partial spin crossover (T1/2 = 180 K) and a quantitative LS to HS photomagnetic conversion at low temperatures, with a T(LIESST) value of 61 K.

Synthesis, crystal structure and photocatalytic properties of two new coordination polymers based on flexible dicarboxylate and 1,1′-(1,4-butanediyl)bis(imidazole) ligands

The assembly of 3,3ˊ-(1,2-phenylenebis(methyleneoxy)) dibenzoic acid (H2L) with CoII/CuII salts in presence of 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) ancillary ligand generated two new coordination polymers (CPs) with formula [Co(L)(bbi)]n (1) and [Cu3(μ2-OH)2(L)2(bbi)]n (2). The crystallographic studies revealed that 1 exhibits 2D layer structure, while 2 displays 1D chain. The photocatalytic activities of title materials have been tested for the degradation of a model organic dye methyl violet (MV). The photocatalytic experimental results demonstrated that both 1 and 2 displayed efficient photocatalytic performances to degrade MV under UV irradiation. The mechanisms of these CPs for photocatalytic behaviour have been proposed.

Four new coordination complexes prepared for the degradation of methyl violent dye based on flexible dicarboxylate and different N-donor coligands

A ether-bridged dicarboxylic acid, 4,4′-{[1,2-phenylenebis-(methylene)]bis(oxy) dibenzoic acid (H2L), was used as highly versatile building block for the hydrothermal generation of a series of coordination polymeric architectures in thepresence of 1,1′-(1,4-butanediyl)bis(imidazole) (bbi) and 1,10-phenanthroline (phen). These were formulated as [Co2(L)2(bbi)·CH3CN]n (1), [Cu(L)(bbi)]n (2), [Co(L)(phen)(H2O)]n (3), and [Cu(L)(phen)(H2O)·2CH3CN]n (4), have been synthesized and characterized. Thenature of the N-donor building blocks and metal ions have a significant effect on the structural diversity. Photocatalytic properties of selected materials were investigated, showing that 2is a promising photocatalyst for the UV-light-driven degradation of methyl violet (MV) as a model organic dye pollutant.

Constructing an Interpenetrated NiII-Based Coordination Polymer Based on a Flexible Dicarboxylate Ligand and an N-Donor Ligand: Preparation, Topological Diversity, and Catalytic Properties

A novel coordination polymer (CP) was constructed using 1,3-bis(4-carboxyphenoxy) propane (H2bcp), 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene (bimb), and NiII ions. [Ni(bcp)(bimb)]·H2O]n (1) shows an interesting 2D+2D → 3D inclined polyrotaxane topology. The structure was characterised by many methods. This work indicates that the flexible and neutral pyridine ligand plays a significant role in constructing CPs. Furthermore, 1 is a highly efficient catalyst for the reaction of CO2 and epoxides.

CdII -Organic Frameworks Fabricated with a N-Rich Ligand and Flexible Dicarboxylates: Structural Diversity and Multi-Responsive Luminescent Sensing for Toxic Anions and Ethylenediamine.

Three metal-organic frameworks {[Cd(L)(glu)]⋅3 H2 O}∞ (1), {[Cd2 (L)2 (adi)2 ]⋅5 H2 O}∞ (2) and {[Cd(L)(sub)]⋅3 H2 O⋅DMA }∞ (3) (L=pyridine-3,5-bis(5-azabenzimidazole), H2 glu=glutaric acid, H2 adi=adipic acid and H2 sub=suberic acid) were obtained under solvothermal conditions. Complex 1 shows a 2D (4,4) network constructing of Cd2 -glu and Cd-L chains. Complex 2 presents a 2-fold interpenetrating 3D framework with pcu topology. Complex 3 is a 3D framework with cds topology. Three complexes with versatile structures were obtained by changing aliphatic dicarboxylate ligands with different lengths based on a N-rich ligand. Moreover, the fluorescence measurements indicate that complex 1 is a good multifunctional chemosensor for the detection of Cr2 O7 2- and MnO4 - anions by fluorescence quenching effect, and ethylenediamine by fluorescence enhancement effect, with detection limits of 1.196 ppm, 0.551 ppm and 64.572 ppm, respectively. Both complexes 2 and 3 can selectively sense Cr2 O7 2- anion with detection limits of 1.126 ppm for 2 and 0.831 ppm for 3 by a fluorescence quenching effect.

Two zinc(ii)-based coordination polymers with flexible dicarboxylate and pyridine mixed ligands: effect of π⋯π interactions on electrical activity

We synthesized two Zn(ii)-based 1D coordination polymers with paddle-wheel units using flexible 1,4-cyclohexanedicarboxylate linkers; these compounds exhibited electrical conductivity and Schottky barrier diode behavior.

Luminescent Coordination Polymers of Naphthalene Based Diamide with Rigid and Flexible Dicarboxylates: Sensing of Nitro Explosives, Fe(III) Ion, and Dyes

A naphthalene based diamide, 3-pyridin-3-yl-N-[5-(3-pyridin-3-yl-acryloylamino)-naphthalen-1-yl]-acrylamide ligand (L) with four dicarboxylates were shown to form Cd/Zn(II) coordination polymers under solvothermal conditions. Three of these coordination polymers (CPs) were found to have 2D-networks, while one of them contains a 3D-network. The Cd(II) centers exhibited bimetallic and trimetallic secondary building units to link the dicarboxylates and ligands. The CPs displayed high luminescence given the presence of electron rich moiety in the ligand. This luminescent property of CPs has been exploited for the detection of nitro aromatics and Fe(III) ions from aqueous solutions of 0.69 μM (0.16 ppm) and 1.29 μM (0.52 ppm) of picric acid and ferric ion, respectively. Further, all the CPs have shown propensity to adsorb dyes such as methylene blue, while eosin-Y is adsorbed by only one of the four CPs. The dye sorption was found to influence the emission profiles in terms of absorption maxima.

Sensitive and Specific Guest Recognition through Pyridinium-Modification in Spindle-Like Coordination Containers.

An elaborately designed pyridinium-functionalized octanuclear zinc(II) coordination container 1-Zn was prepared through the self-assembly of Zn2+ , p-tert-butylsulfonylcalix[4]arene, and pyridinium-functionalized angular flexible dicarboxylate linker (H2 BrL1). The structure was determined by a single-crystal X-ray diffractometer. 1-Zn displays highly sensitive and specific recognition to 2-picolylamine as revealed by drastic blueshifts of the absorption and emission spectra, ascribed to the decrease of intramolecular charge transfer (ICT) character of the container and the occurrence of intermolecular charge transfer between the host and guest molecules. The intramolecular charge transfer plays a key role in the modulation of the electronic properties and is tunable through endo-encapsulation of specific guest molecules.

Crystal structure of poly[[di-μ3-acetato-tetra-aqua-bis-(μ2-cyclo-hexane-1,4-di-carboxyl-ato)dilanth-an-um(III)] dihydrate

The title compound, {[La2(CH3COO)2(C8H10O4)2(H2O)4]·2H2O} n or [La2(ac)2(e,a-cis-1,4-chdc)2(H2O)4]·2H2O, where ac is acetate and 1,4-chdc is cyclo-hexane-1,4-di-carboxyl-ate anion, is a binuclear lanthanum(III) complex. Each metal atom is deca-coordinated by four O atoms from two distinct 1,4-chdc2- ligands, four O atoms from three acetate groups and two O atoms from coordinated water mol-ecules to form a distorted bicapped square-anti-prismatic geometry. Two non-coordinated water mol-ecules are also present in the formula unit. The most remarkable feature of this compound is that it possesses a only cis conformation for cyclo-hexane-1,4-di-carb-oxy-lic acid, although the raw material consists of a mixture of cis and trans isomers. The μ3-η2:η2 coordination mode of the bridging acetate group and the flexible di-carboxyl-ate fragments of 1,4-chdc2- results in the formation of infinite two-dimensional lanthanide-carboxyl-ate layers within the crystal structure. The directionality of strong inter-molecular O-H⋯O and weak C-H⋯O inter-actions provides robustness to the layers, which leads to the construction of a three-dimensional supra-molecular network. The crystal studied was refined as a two-component twin.