Coordinated Water Molecules Research Articles

«Green-Ligand» in Metallodrugs Design-Cu(II) Complex with Phytic Acid: Synthetic Approach, EPR-Spectroscopy, and Antimycobacterial Activity.

The interaction of sodium phytate hydrate C6H18O24P6·xNa·yH2O (phytNa) with Cu(OAc)2·H2O and 1,10-phenanthroline (phen) led to the anionic tetranuclear complex [Cu4(H2O)4(phen)4(phyt)]·2Na+·2NH4+·32H2O (1), the structure of the latter was determined by X-ray diffraction analysis. The phytate 1 is completely deprotonated; six phosphate- fragments (with atoms P1-P6) are characterized by different spatial arrangements relative to the cyclohexane ring (1a5e conformation), which determines two different types of coordination to the complexing agents-P1 and P3, P4, and P6 have monodentate, while P2 and P5 are bidentately bound to Cu2+ cations. The molecular structure of the anion complex is stabilized by a set of strong intramolecular hydrogen bonds involving coordinated water molecules. Aromatic systems of phen ligands chelating copper ions participate in strong intramolecular and intermolecular π-π interactions, further contributing to their association. At the supramolecular level, endless stacks are formed, in the voids of which sodium and ammonium cations and water molecules are present. The stability of 1 in the presence of human serum albumin (HSA) was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. Continuous wave (CW) EPR spectra in water/glycerol frozen solution clearly indicate a presence of an exchange-coupled Cu(II)-Cu(II) dimeric unit, as well as a Cu(II) monomer-like signal arising from spins sufficiently distant from each other, with comparable contributions of two types of signals. In the presence of albumin at a 1:1 ratio (1 to albumin), the EPR spectrum changes significantly, primarily due to the reduced contribution of the S = 1 fraction showing dipole-dipole splitting. The biological activity of 1 in vitro against the non-pathogenic (model for Mycobacterium tuberculosis) strain of Mycolicibacterium smegmatis is comparable to the first-line drug for tuberculosis treatment, rifampicin.

Crystal structures of zinc(II) coordination complexes with isoquinoline N-oxide

The reaction of one equivalent of zinc(II) halide salts with two equivalents of isoquinoline N-oxide (iQNO; C9H7NO) in methanol yields compounds of the general formula [ZnX 2(iQNO)2], with X = Cl− (I), Br− (II) and I− (III). However, starting with zinc(II) perchlorate or nitrate leads to the formation of complex ions with the compositions [Zn(iQNO)6](X)2 for X = ClO4 − (IV), and [Zn(iQNO)(H2O)5](iQNO)2 X 2 for X = NO3 − (V). Complexes (I), (II) and (III), namely dichloridobis(isoquinoline N-oxide-κO)zinc(II) [ZnCl2(C9H7NO)2], dibromidobis(isoquinoline N-oxide-κO)zinc(II) [ZnBr2(C9H7NO)2], and diiodidobis(isoquinoline N-oxide-κO)zinc(II) [ZnI2(C9H7NO)2], each exhibit a distorted tetrahedral coordination geometry around the zinc(II) ion coordinated by two iQNO ligands bound through the oxygen atom and two halide ions. The zinc ion lies on a crystallographic twofold axis in the bromo complex. The X—Zn—X bond angles are approximately 15–17° larger than the O—Zn—O bond angles resulting in the observed tetrahedral distortion. In complex (IV), hexakis(isoquinoline N-oxide-κO)zinc(II) bis(perchlorate), [Zn(C9H7NO)6](ClO4)2, the zinc(II) ion occupies a special position with 3 site symmetry and is octahedrally coordinated by six iQNO ligands, albeit with slight distortions evidenced by a spread of cis bond angles from 85.82 (4) to 94.18 (4)°. The chlorine atom of the perchlorate anion lies on a crystallographic threefold axis. Finally, complex (V) crystallizes with a pseudo-octahedral geometry; pentaaqua(isoquinoline N-oxide-κO)zinc(II) dinitrate–isoquinoline N-oxide (1/2), [Zn(C9H7NO)(H2O)5](NO3)2·2(C9H7NO). The nitrate ions and non-coordinated iQNO molecules engage in π-stacking and hydrogen-bonding interactions with the coordinated water molecules. The iQNO—Zn—O equatorial bond angles range from 88.98 (9) to 94.90 (9)°, with the largest deviation from a perfect octahedral angle attributed to the influence of a weak C—H...O (from water) interaction (2.287 Å) involving the bound iQNO ligand.

Isolation of Inner-Sphere Aquo Complexes of Samarium(II).

The cis-anti-cis and cis-syn-cis isomers of [Sm(dicyclohexano-18-crown-6)(H2O)2]I2 exhibiting trans water molecules bound to the Sm2+ ion have been isolated and characterized. Sm2+ possesses an electrochemical potential sufficient for water reduction, and thus these complexes add to the recent body of evidence that the oxidation of Sm2+ by water can operate by a mechanism that is not straightforward. These complexes are obtained by the direct addition of stoichiometric amounts of water to solutions of the respective Sm(dicyclohexano-18-crown-6)I2 isomers under an inert atmosphere. The parent complex, Sm(dicyclohexano-18-crown-6)I2, lacking coordinating water molecules can be obtained through rigorous exclusion of water. It was determined that the bulky cyclohexano-substituents deter intramolecular interactions between [Sm(dicyclohexano-18-crown-6)(H2O)2]I2 complexes and slow the oxidization of the metal centers. The extent of the stability of these complexes to the presence of water has been further probed through cyclic voltammetry, where it was found that the redox potential of both isomers of [Sm(dicyclohexano-18-crown-6)(H2O)2]I2 maintains quasi-reversible behavior with a 50,000-fold excess of water to Sm2+ in solution with the cis-syn-cis complex being quasi-reversible at even higher concentrations of water. Solution-phase spectroscopy of these complexes in acetonitrile shows a corresponding hypsochromic shift of the Sm2+ 4f → 5d transition typically observed in the visible region from Sm2+ complexes. The crystalline compounds obtained in this study support solid-state spectroscopic trends observed from other Sm2+ crown-ether complexes containing iodide counterions, wherein the proximity of the iodide ions to the metal center determines whether the complex can exhibit 4f → 4f photoluminescence.

Constructing a Self-Referenced NIR-II Thermometer with Energy Tuning of Coordinating Water Molecules by a Minimalist Method.

Fluorescence thermometry based on metal halide perovskites is increasingly becoming a hotspot due to its advantages of high detection sensitivity, noninvasiveness, and fast response time. However, it still presents certain technical challenges in practical applications, such as complex synthesis methods, the use of toxic solvents, and being currently mainly based on the visible/first near-infrared light with poor penetration and severe autofluorescence. In this study, we synthesize the second near-infrared (NIR-II) luminescent crystals based on Yb3+/Nd3+-doped zero-dimensional Cs2ScCl5·H2O by a simple "dissolve-dry" method. The whole synthesized process does not involve high temperatures or high pressures. Cs2ScCl5·H2O/Yb3+,Nd3+ has an optimum fluorescence performance when the Yb3+/Nd3+ doping amount is 15%/20%. The emission intensity ratio attributed to Yb3+ and Nd3+ varies with temperature, and this variation is exacerbated due to the fact that the 2F5/2 energy level of Yb3+ can be effectively aligned with the O-H bond stretching vibration energy of coordinating water molecules to facilitate energy transfer. Ultimately, the crystals can act as self-referenced ratiometric NIR-II luminescent thermometers with a maximum relative sensitivity of 1.66% K-1 at 323 K. This work highlights the advantages of NIR-II luminescent materials for temperature sensing, which is significant for advancement in the field of noncontact thermometers.

CRYSTAL STRUCTURE OF INCLUSION COMPOUND OF POROUS LUTETIUM(III) TRANS-THIENOTHIOPHENE-2,5-DICARBOXYLATE WITH TRANS-CINNAMALDEHYDE

A new inclusion compound of cinnamic aldehyde (cin) based on porous lutetium(III) trans-thienothiophene-2,5-dicarboxylate (ttdc2–) metal-organic framework was character-ized by means of single-crystal XRD, IR, CHN and TGA methods. The title crystal struc-ture with the formula [Lu2(H2O)2(ttdc)3]·2DMF·cin (1cin) was derived from the parent MOF [Lu2(H2O)2(ttdc)3]·4DMF (1DMF) upon slow solid-to-liquid solvent exchange. Cin-namal molecules, well-resolved within the structure of rigid coordination network, are hydrogen-bonded to the H atom of coordinated water molecule. Close π…π-stacking con-tacts between the coplanar propene fragments, capable for possible [2+2] cycloaddition reactions, and unusual for cinnamal inclusion compounds, were found between the neighbor guest molecules in the crystal structure.

Study on gas adsorption and separation performance of alkyl functionalized MOF materials under wet conditions.

Metal-organic framework materials exhibit significant potential for diverse applications in gas adsorption and separation. We have studied the performance changes of Cu-BTC, Cu-MBTC and Cu-EBTC under different water-containing conditions. GCMC studies shows that, compared with Cu-BTC, the water absorption properties of Cu-MBTC and Cu-EBTC have a certain degree of decline, which is consistent with the experimental results. The incorporation of alkyl groups led to a decrease in the heat of adsorption for both Cu-MBTC and Cu-EBTC when exposed to water. The gas adsorption performance of Cu-BTC, Cu-MBTC and Cu-EBTC exhibits inconsistent variations in gas adsorption performance under water-containing conditions. The addition of coordinated water molecules enhances the ability of Cu-BTC to adsorb CO2. The capacity of Cu-MBTC with 4 wt% water to adsorb CO2 increased, but the capacity of Cu-MBTC with 8 wt% water to adsorb CO2 decreased. The presence of coordinated water molecules reduces the CO2 adsorption performance of Cu-EBTC. The study of the heat of adsorption explains this phenomenon from the mechanism. At the same time, we found an interesting phenomenon. The existence of trace water molecules can greatly improve the adsorption selectivity of Cu-EBTC to CO2/N2, while the pressure and gas ratio have little effect. It can provide more possibilities for the widespread use of MOF in the fields of gas adsorption and separation.

Crystal structure of di-μ-acetato-κ4 O:O'-bis{(acetato-κ2 O,O')tetra-aqua-[1-(pyridin-2-yl-methylidene-κN)-2-(pyridin-2-yl-κN)hydrazine-κN 1]lanthanum(III)} dinitrate hemihydrate.

In the binuclear title complex, [La2(C2H3O2)4(C11H10N4)(H2O)4](NO3)2·0.5H2O, the two lanthanum ions are nine coordinate in a distorted trigonal-prismatic geometry. Each LaIII ion is bonded to three N atoms of the Schiff base, 1-(pyridin-2-yl)-2-(pyridin-2-yl-methyl-ene)hydrazine and is coordinated by one acetate group, which acts in η 2-bidentate mode and two acetate groups that act in μ 2-mode between the two LaIII ions. Two η 1-water mol-ecules complete the coordination sphere. All bond lengths in the coordination environment of the LaIII ion are slightly larger than those observed in the isostructural NdIII and SmIII complexes. The LaIII⋯LaIII distance is 4.6696 (6) Å. In the crystal, extensive O-H⋯O hydrogen-bonding inter-actions involving the coordinated water mol-ecules and the non-coordinating nitrate anions, as well as the oxygen atoms of the acetate groups, generate an overall three-dimensional supra-molecular network.

In Ukrainian

The molecular models of tin dioxide nanoparticles containing 1 – 10 metal atoms and can include coordinated or constitutive water were constructed. Their equilibrium spatial structure and electronic structure are calculated using the second-order Möller – Plesset perturbation theory with the SBKJC valence basis set. It is shown that the length of the Sn–O bond in nanoclusters does not depend on their size and the coordination number of Sn atoms, but is determined by the coordination type of neighboring oxygen atoms. Namely, the Sn–O(3) bond length (~ 2.10 Å) > the Sn–O(2) bond length (~ 1.98 Å). The obtained Sn–O(3) bond lengths are in good agreement with the experimental values for crystalline SnO2 samples (2.05 Å). The calculated atomization energy for SnO2 is 1661 kJ/mol and satisfactorily corresponds to the experimentally measured specific atomization energy of crystalline SnO2 (1381 kJ/mol). It was found that a satisfactory reproduction of the experimental characteristics of crystalline tin dioxide is possible when using clusters containing at least 10 tin atoms, for example, (SnO2)10×14H2O. Based on the analysis of the energy effects of coordination of water molecules and hydroxide ion, proton removal and proton transfer on the hydrated surface of tin dioxide, quantitative estimates of the acid-base characteristics of the active centers of the SnO2 surface were made. The dependence of the acidity of hydroxyl groups and coordinated water molecules on the coordination number of the oxygen atom and the neighboring tin atom, as well as on the size of the cluster model, was revealed. It has been shown that the acidity of proton and aproton centers naturally decreases with increasing coordination number of the tin atom. The methodology used in this work to calculate the рКа value of the smallest model of the SnO2×H2O composition allows us to reproduce the experimental data for stannous acids. The mechanisms of formation of the simplest nanostructures from the initial forms of stannous hydroxide Sn(OH)4 are proposed. It has been shown that the formation of a dimer (SnO2)2×4H2O by the association of two Sn(OH)4 molecules is energetically most advantageous. Further transformations of nanoparticles lead to an increase in their size, dehydration, and the formation of denser structures that have crystallinity features inherent in solid-phase SnO2.

Identifying and tuning coordinated water molecules for efficient electrocatalytic water oxidation

Identifying and tuning coordinated water molecules for efficient electrocatalytic water oxidation

Slow Relaxation of the Magnetisation in a Two-Dimensional Metal–Organic Framework with a Layered Square Lattice

Herein, we present the synthesis and structural characterisation of two layered MOFs with the asymmetric ligand 3-chloro,6-cyano-2,5-dihydroxy-1,4-benzoquinone dianion (C6O4(CN)Cl2− = chlorocyananilato). These compounds, formulated as (H3O)[Eu(C6O4(CN)Cl)2(H2O)]·34H2O (1) and (H3O)[Dy(C6O4(CN)Cl)2(H2O)]·44H2O (2), are isostructural and show a (4,4)-layered square structure with the crystallisation water molecules located between the layers. The lanthanoid ions are surrounded by four bis-bidentate chlorocyananilato ligands that connect each LnIII centre with other four, giving rise to square cavities formed by LnIII centres in the vertices and chlorocyananilato ligands as the sides. There is an additional coordinated water molecule that occupies the caped position of the capped square antiprismatic coordination geometry around the LnIII centres. The magnetic properties show the presence of a field-induced slow relaxation of the magnetisation in the DyIII derivative at low temperatures that follows Direct and Orbach relaxation mechanisms with an energy barrier of 36(3) K.

Cationic Coordination Modification Drives Birefringence and Nonlinear Effect Double Lifting in Sulfate.

As nonlinear optical (NLO) crystals, sulfates have the superiority of transparency for ultraviolet (UV) light, but they are often troubled by small nonlinear coefficients and birefringence owing to the high symmetry of the [SO4]2- group. By introducing two neutral diethylenetriamine (DETA) molecules to replace the six coordinated water molecules of the [Zn(H2O)6]2+ complex cation in [Zn(H2O)6](SO4)(H2O), a new sulfate with an acentric structure, namely, [Zn(DETA)2](SO4)(H2O)3, has been designed and synthesized. Structural investigation reveals that the coordination modification of Zn2+ ion tremendously enhances its intraoctahedral distortion. The formed distorted [Zn(DETA)2]2+ cations and the [SO4]2- groups feature an optimized arrangement, endowing [Zn(DETA)2](SO4)(H2O)3 with enhancements in both second harmonic generation (SHG) intensity, from undetectable to 0.25 × KH2PO4 (KDP), and birefringence, from 0.014 to 0.042 at 1064 nm. Despite the slight compromise made in the light transmission range, [Zn(DETA)2](SO4)(H2O)3 still possesses a short absorption edge of 220 nm, retaining the majority of the light transmission range in the solar-blind region. Our work provides a novel and applicable approach of cationic coordination modification to improve the nonlinear optical coefficient and birefringence of sulfates.

Evaluation of structurally related acyclic ligands OBETA, EHDTA, and EGTA for stable Mn2+ complex formation.

In recent years, significant research efforts have been dedicated to finding efficient and safe alternatives to the currently used gadolinium (Gd)-based MRI contrast agents. Among the most explored alternatives are paramagnetic chelates of the Earth-abundant Mn2+, which form a prominent class of metal complexes. The design of Mn2+ complexes with enhanced relaxation properties and improved safety profiles hinges on a delicate balance between thermodynamic and kinetic stability, as well as the presence of coordinated water molecules. In this study, we present a comprehensive investigation into the coordination chemistry of three structurally related polyetheraminocarboxylic chelating agents. Our aim is to elucidate the structural features, paramagnetic properties, and thermodynamic and kinetic inertness of the corresponding Mn2+ complexes. The most significant finding is the considerable difference in the dissociation rates of the complexes, with the octadentate EGTA complex being the most labile. The observed dissociation rates correlate well with the nitrogen inversion dynamics, as assessed through NMR spectral analysis of the analogous Zn2+ complexes.

Synthesis and X-ray Structures of Polymeric Calcium Carboxylates

The reactions of calcium hydroxide with pivalic, 1-naphthoic, and 2-furancarboxylic acids afford the corresponding polymeric calcium carboxylates. Depending on the crystallization conditions, calcium pivalate is isolated as two different coordination polymers: [Ca3(Piv)6(DMF)2]n · 0.635nC6H6 · 0.365nDMF (I) and [Ca(Рiv)(H2O)2.333(DMF)0.666]n · nРiv·0.333H2O (II). The synthesized calcium 1-naphthoate contains coordinated water molecules [Сa(Naph)2(H2O)2]n (III), and calcium furoate [Ca(Fur)2]n (IV) contains no ancillary ligands. The structures of compounds I–IV are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2342790–2342793, respectively). The structures of compounds I–III are characterized by the 1D polymeric structure, and compound IV is the 3D polymer.

Upconversion Luminescence with Bis-pyclen Yb(III) Chelates: Crown vs. Linear Polyether Linkers in Discrete Heteropolynuclear Architectures.

Ligands combining two lateral bis-pyridyl-phosphonated-pyclens were synthesized, using a flexible linear pegylated linker (L2) or a bulkier K22 crown-ether (L3). A functionalized pyridyl-phosphonated-pyclen (L1) was also prepared as a mononuclear analogue. Coordination behavior of lanthanide cations was studied via NMR titration with Lu for L1, and UV/Vis and luminescence spectroscopy with Yb for L2/L3. Strong coordination of two Yb atoms enabled isolation and spectroscopic characterization of dinuclear complexes in H2O and D2O. Excited state lifetime analysis at 980 nm revealed strong protection of Yb cations, with no coordinated water molecule. Upon titration of the isolated dinuclear Yb complexes with Tb cations, cooperative upconversion (UC) sensitization of Tb in the visible was observed upon excitation of Yb at 980 nm in D2O. In the absence of Tb, the Yb complexes also exhibited cooperative luminescence with a weak emission band around 500 nm upon NIR Yb excitation. Efficient UC with Tb was only observed after thermal treatment, suggesting a slow kinetic of formation of the UC species. [Yb2TbL3] showed weak Tb centered UC emission, while the dinuclear complex of L2 displayed more intense UC emission up to two equivalents of Tb, forming [(Yb2L2)Tbx] (x=1-2), with the tetranuclear heterometallic complex being the most intense emitter. Log-Log plot analysis confirmed the two-photon nature of the UC process.

Enhancing Sodium‐Ion Storage Capacity and Stability in Metal–Organic Coordination Compounds by Bifunctional Coordinated Water Molecule

Redox‐active organic compounds have received much attention as high‐capacity electrodes for rechargeable batteries. However, the high solubility in organic electrolytes during charge and discharge processes hinders the practical exploitation of organic compounds. This study presents a cobalt‐based metal–organic coordination compound with bifunctional coordinated water (Co‐MOC‐H2O) for sodium‐ion storage. The coordinated water enhances interactions between sodium ions and nitrogen atoms in organic ligands through chelation, activating the inert sodium‐ion storage sites (C=N). Moreover, the stable hydrogen bonded framework formed by the coordinated water molecules prevents the active organic compounds from dissolving into the electrolyte, thereby enhancing cycling stability. With the bifunctional coordinated water molecules, the Co‐MOC‐H2O electrode delivers a high capacity of 403 mAh g−1 at 0.2 A g−1 over 600 cycles and exhibits a capacity retention of 77.9% at 2 A g−1 after 1100 cycles. This work highlights the crucial role of the coordinated water molecules in constructing high capacity and long‐life sodium‐ion storage materials.

Chiral Supramolecular Proton Conductors: Harnessing Highly Charged Zirconium-Amino Acid Oxo-Clusters.

Incorporation of amino acid capping molecules (alanine (Ala), methionine (Met), phenylalanine (Phe), tryptophan (Trp), tyrosine (Tyr), and valine (Val)) in their zwitterionic form into archetypal [Zr6(μ3-O)4(μ3-OH)4]12+ clusters creates supramolecular frameworks in which the assembly of these highly charged discrete units with chloride counterions provides a unique combination of porosity, chirality, and proton conductivity. The supramolecular frameworks assembled from these cluster entities (i.e., ZrAla, ZrMet, ZrPhe, ZrTrp, ZrTyr, and ZrVal) are based on the counterbalancing of the cationic hexanuclear entities by chloride anions. The resulting structures provide porous structures (except ZrVal) with variability of chemical and structural stability based on their supramolecular interactions. Among these compounds, ZrPhe and ZrVal remain stable due to the presence of a double chelation-like interaction involving four hydrogen bonds formed between a chloride anion, two ammonium groups, and two coordinated water molecules from two adjacent hexanuclear units. The presence of multiple acidic proton positions and strong hydrogen-bond donor/acceptor groups on the water channels gives rise to easy proton conduction pathways within the structures. In fact, ZrPhe and ZrVal, together with ZrTyr, exhibit high proton conductivity values with varying dependencies on the atmospheric humidity. Finally, the correlation between proton conduction and porosity is discussed.

Enhancing ethanol/water separation in UTSA-280 by a pore engineering strategy

Dehydration of ethanol is the key issue for the production of bioethanol fuel. Based on energy-efficient water-adsorptive mechanism and size sieving effect of ultramicroporous metal–organic framework, UTSA-280 is a promising candidate for high purity ethanol production. But it is still a challenge to improve the water adsorption capacity of UTSA-280 without compromising the separation selectivity. Here, we present a post-synthetic pore engineering strategy towards coordinated water adjustment for UTSA-280 to address this challenge. Partial coordinated water molecules have been successfully removed in UTSA-280·xPCW. By reversible desorption and resorption of water to Ca ions, the saturated water adsorption of UTSA-280·xPCW increased up to 2.6 mol/mol (exceeding 60 % that of original UTSA-280). The enhancing effect were supported by both kinetics and thermodynamics mechanisms. Dynamic vapor breakthrough results showed that UTSA-280·41PCW produced the largest amount of pure ethanol (22.46 mmol/g) and highest water/ethanol separation factor (15.9), providing a synchronized enhancement of water adsorption and ethanol/water separation. UTSA-280·xPCW are promising candidates for the dehydration of ethanol.

Water Sorption on Isoreticular CPO-27-Type MOFs: From Discrete Sorption Sites to Water-Bridge-Mediated Pore Condensation.

Pore engineering is commonly used to alter the properties of metal-organic frameworks. This is achieved by incorporating different linker molecules (L) into the structure, generating isoreticular frameworks. CPO-27, also named MOF-74, is a prototypical material for this approach, offering the potential to modify the size of its one-dimensional pore channels and the hydrophobicity of pore walls using various linker ligands during synthesis. Thermal activation of these materials yields accessible open metal sites (i.e., under-coordinated metal centers) at the pore walls, thus acting as strong primary binding sites for guest molecules, including water. We study the effect of the pore size and linker hydrophobicity within a series of Ni2+-based isoreticular frameworks (i.e., Ni2L, L = dhtp, dhip, dondc, bpp, bpm, tpp), analyzing their water sorption behavior and the water interactions in the confined pore space. For this purpose, we apply water vapor sorption analysis and Fourier transform infrared spectroscopy. In addition, defect degrees of all compounds are determined by thermogravimetric analysis and solution 1H nuclear magnetic resonance spectroscopy. We find that larger defect degrees affect the preferential sorption sites in Ni2dhtp, while no such indication is found for the other materials in our study. Instead, strong evidence is found for the formation of water bridges/chains between coordinating water molecules, as previously observed for hydrophobic porous carbons and mesoporous silica. This suggests similar sorption energies for additional water molecules in materials with larger pore sizes after saturation of the primary binding sites, resulting in more bulk-like water arrangements. Consequently, the sorption mechanism is driven by classical pore condensation through H-bonding anchor sites instead of sorption at discrete sites.

Enhanced Electrochemical Performance of Copper(II) Metal Organic Framework‐Ternary Quantum Dots Composite towards the Detection of Bisphenol A

AbstractTernary quantum dot metal organic framework (MOFs) composite sensor formulated as (ZnInSe2@[Cu(2‐HNA)2(H2O)]) with an enhanced electrochemical performance was synthesized from a copper(II) metal‐organic framework complex ([Cu(2‐HNA)2(H2O)]) and ZnInSe2 ternary quantum dot (TQDs). The compounds were characterized by Fourier transform infrared spectroscopy, Ultraviolet‐Visible spectroscopy, transmission electron microscopy, scanning electron microscopy, single crystal X‐ray crystallography, and photoluminescence. Molecular structure of the copper(II) complex revealed a distorted square pyramidal geometry with two molecules of 2‐hydroxy‐1‐naphthaldedyde at the basal planes as bidentate chelating ligands with a coordinated water molecule at the apical position. TEM micrographs revealed monodispersed composite with an average particle size of 3.2 nm. The composite and its precursors were used as ectrochemical sensor for the detection of bisphenol A, using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The composite modified on a gold electrode exhibited enhanced electrochemical performance in comparison to those of the MOFs and TQDs. The reaction process at the surface of the modified electrode with the composite is diffusion controlled with a limit of detection, and limit of quantitation of 4.70 nM and 14.26 nM over a concentration range of 10–50 nM (S/N=3). The gold modified composite electrode is stable and could serve as a model for the development of electrochemical sensor to determine BPA.

Proton Conduction via Water and Ammonia Coordinated Metal Cationic Species in MOF and MHOF Platforms.

Although metal-organic frameworks (MOFs) and metalo hydrogen-bonded organic frameworks (MHOFs) are designed as promising solid-state proton conductors by incorporating various protonic species intrinsically or extrinsically, design and development of such materials by employing the concept of proton conduction through coordinated polar protic solvent is largely unexplored. Herein, we have constructed two proton-conducting materials having different solvent coordinated metal cationic species: In-H2O-MOF, ({[In(H2O)6][In3(Pzdc)6] ⋅ 15H2O}n; H2Pzdc: pyrazine-2,3-dicarboxylic acid) with coordinated water molecules from hexaaquaindium cationic species, and MHOF-4, ([{Co(NH3)6}2(2,6-NDS)2(H2O)2]n; 2,6-H2NDS: 2,6-naphthalenedisulfonic acid) with coordinated ammonia from hexaammoniacobalt cationic species. Interestingly, higher proton conductivity was achieved for In-H2O-MOF (1.5×10-5 S cm-1) than MHOF-4 (6.3×10-6 S cm-1) under the extreme conditions (80 °C and 95 % RH), which could be attributed to enhanced acidity of coordinated water molecules having much lower pKa value than that of coordinated ammonia. Greater charge polarization on hydrogen atoms of In3+-coordinated water molecules than that of Co2+-coordinated ammonia led to the high conductivity of In-H2O-MOF, as evident by quantum chemical studies. Such a comparative study on metal-coordinated protic polar solvents in achieving proton conduction in crystalline solids is yet to be made.