Kinetics and mechanism of the oxidation of formic and oxalic acids by benzyltrimethylammonium dichloroiodate

The oxidation of formic and oxalic acids by benzyltrimethylammonium dichloroiodate (BTMACI), in the presence of zinc chloride, leads to the formation of carbon dioxide. The reaction is first order with respect to BTMACI, zinc chloride and organic acid. Oxidation of deuteriated formic acid indicates the presence of a kinetic isotope effect. Addition of benzyltrimethylammonium chloride enhances the rate. It is proposed that the reactive oxidizing species is [(PhCH₂Me₃N)⁺ (IZn₂Cl₆)^-]. Suitable mechanisms have been proposed.     

Tandem magnetization and post‐synthetic metal ion exchange of metal–organic framework: Synthesis,characterization and catalytic study

For the first time, metal‐exchange in a magnetic metal–organic framework (MOF) via tandem magnetization and post‐synthetic modification has been developed. The new magnetic mixed‐metal metal–organic framework nanocomposite, CoFe₂O₄/[Cu_0.63/Zn_0.37‐TMU‐17‐NH₂] (CoFe₂O₄/[Cu/Zn‐MOF]) has been synthesized by immersing the CoFe₂O₄/Zn‐TMU‐17‐NH₂ (CoFe₂O₄/Zn‐MOF) as a template in DMF solution of Cu (II) salts. CoFe₂O₄/[Cu/Zn‐MOF] showed to be a highly reactive and easily recoverable magnetic catalyst for the preparation of tetrazole derivatives via one‐pot three‐component reactions of different aldehydes with hydroxyl amine hydrochloride and sodium azide. Our results (Fourier transform‐infrared, inductively coupled plasma‐optical emission spectroscopy, powder X‐ray diffraction, field emission‐scanning electron microscopy, energy‐dispersive X‐ray spectroscopy‐mapping and vibrating‐sample magnetometer) show successful partial metal‐exchange in which the framework integrity remained intact during the metal‐exchange process.     

Influence of the composition of compositions based on organic compounds and chelate complexes of aluminun and yridium on their electroluminescent properties

The effect of the composition of electroluminescent compositions based on PEDOT, TPD, Alq₃, and Ir(PPy)₃, the structure of the cathode (Al, CaMg/Ag, Al/Ag), and the possibility of forming of emitting layers (thermovacuum deposition and centrifugation) on their current-voltage, voltage-brightness, and spectral characteristics has been studied. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 54–58, January–February, 2009.     

Prompt and Long-Lived Anti-Kasha Emission from Organic Dyes

Anti-Kasha behavior has been the subject of intense debate in the last few years, as demonstrated by the high number of papers appearing in the literature on this topic, dealing with both mechanistic and applicative aspects of this phenomenon. Examples of anomalous emitters reported in the last 10 years are collected in the present review, which is focused on strictly anti-Kasha organic molecules displaying radiative deactivation from S_n and/or T_n, with n greater than 1.     

Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

Kinetics and mechanism of oxidation of formic and oxalic acids by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is carbon dioxide. The reaction is first-order with respect to QFC. Michaelis-Menten type of kinetics were observed with respect to the reductants. The reaction is acid-catalysed and the acid dependence has the form: k_obs =a +b[H⁺]. The oxidation of α-deuterioformic acid exhibits a substantial primary kinetic isotope effect (k_H/k_D = 6.01 at 303 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft’s and Swain’s multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate-determining step. Suitable mechanisms have been proposed.     

Preparation and Characterization of Hybrid Oxyethylene/Siloxane Electrolyte Systems

One of the most significant consequences of technological evolution in the workplace has been a dramatic increase in the need for portable energy storage. This evolution has occurred, not only with respect to the number of devices, but also in their average energy storage capacity. An obvious commercial consequence has been an increased pressure to develop improved active materials for power sources and more efficient methods for battery production. In recent decades the growth of the commercial market for high performance batteries has been based on the development of both solid‐state and gel electrolytes. The incorporation of these electrolytes as components of various devices (advanced batteries, smart windows, displays and super‐capacitors) offers significant advantages relative to traditional electrolytes, including enhanced reliability and improved safety. The xerogel matrices prepared in this study are represented as U(900) and U(600) and contain 15.5 or 8.5 oxyethylene structural units (CH₂CH₂O) respectively. The oxyethylene chains are bonded at each end to a siliceous intersection through urea bridging links. These sol‐gel derived oxyethylene /siloxane xerogels (designated as di‐ureasils) were doped with controlled amounts of LiAsF₆ or LiSbF₆ to prepare a range of electrolyte compositions. The compositions prepared, with 200>n≥2.5 (where the salt content is expressed as n, the molar ratio of oxyethylene moieties to Li⁺ ions), were characterized by electrochemical and thermal techniques. Preliminary tests performed with a prototype electrochromic device (ECD) incorporating the most promising electrolyte composition, d‐U(900)₈LiAsF₆ as electrolyte and WO₃ as cathodic electrochromic layer, are extremely encouraging.     

Xantphos Doped POPs‐PPh3 as Heterogeneous Ligand for Cobalt‐Catalyzed Highly Regio‐ and Stereoselective Hydrosilylation of Alkynes

A Co(acac)₂/POL‐Xantphos@10PPh₃‐catalyzed hydrosilylation of unsymmetrical internal alkynes with Ph₂SiH₂ has been developed for the synthesis of highly selective syn‐α‐vinylsilane products. Furthermore, terminal alkynes were also used and gave the products with excellent regioselectivity and a wide functional group tolerance. Because this porous organic polymer combines the selectivity and activity merits of Xantphos with the stability advantage derived from the high concentration of PPh₃, the Co(acac)₂/POL‐Xantphos@10PPh₃ can be recycled multiple times without loss of activity and selectivity. This heterogeneous catalyst is expected to find promising applications in industrial synthesis.     

Determination of Volatile Halogenated Compounds in Tap and Surface Waters from the Gdańsk District

Abstract

The present method is based on preconcentration of organic contaminants on XAD-4 as sorbent, thermal desorption, mineralization and coulometric argentometric titration for the final determination of halides. The results were calculated as the total parameter VOX (volatile organic halogen) expressed as chlorine. The method has been used for the VOX determination in tap water, Vistula river water and Baltic Sea water. Sampling of the Baltic Sea water has been carried out during the research cruise of the r/v ‘Oceania’. The relatively high anthropogenic pollution of the river Vistula (c _vox = 11–45 μg Cl/cd³), Gulf of Gdańsk (c _vox = 0.6–4.5 μg Cl/dm³) and the Pomerania Bay (c _vox = 2 μg Cl/dm³) has been determined. The VOX concentration in the tap water varied between 13 and 56 μg/dm³; that is, this water is seriously polluted by volatile organic halogen compounds.     

Assembly of three 3-D MOFs from 2-phenyl-4,5-imidazole dicarboxylate and oxalate

Three lanthanide–organic polymers, {[Ln(μ ₃-HPhIDC)(μ ₂-C₂O₄)_0.5(H₂O)]?·?2H₂O} _n (Ln?=?Nd (1), Sm (2), and Tb (3)), have been isolated from the reaction of 2-phenyl-1H-imidazole-4,5-dicarboxylic acid (H₃PhIDC) with equal amount of Ln(III) salts under solvothermal condition with the rigid coligand oxalate. The three polymers, which are isomorphous and isostructural, have been structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction. Each exhibits a 3-D framework constructed from infinite 2-D layers joined by μ ₂-C₂O₄, which are composed of μ ₃-HPhIDC^2? and trivalent lanthanide. Thermal properties have also been investigated.     

2D Semiconducting Metal–Organic Framework Thin Films for Organic Spin Valves

2D conductive metal–organic frameworks (2D c‐MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the spin‐polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer‐by‐layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c‐MOF, Cu₃(HHTP)₂, (HHTP: 2,3,6,7,10,11‐hexahydroxytriphenylene), with tunable thicknesses on the La_0.67Sr_0.33MnO₃ (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu₃(HHTP)₂/Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c‐MOFs in spintronics.     

Ab initio investigation of 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole for the design of efficient organic field‐effect transistors

The initial molecular structure of 2,2′‐bis(4‐trifluoromethylphenyl)‐ 5,5′‐bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron λ_e, the reorganization energy of hole λ_h, adiabatic electron affinity (EA_a), vertical electron affinity (EA_v), adiabatic ionization potential (IP_a), and vertical ionization potential (IP_v) using DFT. Based on the evaluation of hole reorganization energy, λ_h, and electron reorganization energy, λ_e, it has been predicted that 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field‐effect transistors. © 2015 Wiley Periodicals, Inc.     

Polyoxometalates decorated with metal-organic moieties as new molecular photo- and electro-catalysts

Abstract

Three new polyoxometalate-based organic-inorganic hybrid compounds (POIHCs), [Cu(PBI)₂(H₂O)][{Cu(PBI)(OH)(H₂O)}{PW₁₂O₄₀}]·5H₂O (1), [Cu(PBI)₂(H₂O)][{Cu(PBI)₂(H₂O)}{SiW₁₂O₄₀}]·4H₂O (2) and [Cu₄(HPO₄)(PO₄)(H₂O)₂(PBI)₄][PMo₁₂O₄₀]·H₂O (3) (PBI =2-(pyridin-2-yl)-1H-benzo[d]imidazole), have been synthesized under hydrothermal conditions. All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. In 1 and 2, the Keggin-type polyoxometalate (POM) units are decorated by the {Cu/PBI} metal-organic fragments, together with additional {Cu/PBI} isolated cations, which further stack into 3-D supramolecular frameworks with porous structural features. Compound 3 consists of a rare cationic cluster [Cu₄(HPO₄)(PO₄)(H₂O)₂(PBI)₄]³⁺ and the Keggin-type POM anion, forming a 3-D supramolecular framework with limited interspaces for the entry of guest molecules. Comparable photocatalytic properties of 1–3 were investigated by the use of methylene blue (MB) and Rhodamine B (RhB) degradation under UV light. All compounds showed good catalytic activity for the degradation of MB in contrast to RhB. The possible catalytic mechanism was discussed based on the size of dye molecules, the low adsorption ability and crystal packing mode of the as-synthesized compounds. Additionally, the electrochemical properties of 1–3 have also been investigated, exhibiting good electrocatalytic performance for nitrite reduction.     

Computational approach on architecture and tailoring of organic metal complexes derived from streptomycin and Zn,Cd and Pb: antimicrobial effectiveness

Streptomycin has been used to derive organic metal complexes (OMCs) after metallation with ZnCl₂, CdCl₂ and PbCl₂ and characterized by elemental analysis, electronic and vibrational spectroscopy, ¹H and ¹³C NMR, mass spectroscopy (time‐of‐flight MS), magnetic measurement, thermal decomposition analysis (TGA, DTA), molecular modeling and X‐ray powder diffraction. OMCs are monomeric. Crystal system, lattice parameters, unit cell, particle size and volume of crystalline OMCs have been determined using X‐ray powder diffraction pattern analysis. The geometries of complexes were optimized on the basis of molecular modeling. Kinetic parameters were computed from thermal analysis, confirming first‐order kinetics. Molecular models have been optimized by MM2 calculations. Architecture and tailoring of the rationally designed and synthesized supramolecular models having covalent bonded oxygen or other molecular contacts extended through Huckel Charge Distribution in highest occupied molecular orbit (HOMO). Antimicrobial effectiveness of OMCs has been reported. Copyright © 2011 John Wiley & Sons, Ltd.     

Multi-component hydrogen-bonding salts formed between imidazole and aromatic acids: Synthons cooperation and crystal structures

Imidazole base was crystallized with different aromatic carboxylic acids 2,4-dihydroxybenzoic acid, 5-chlorosalicylic acid, and 1,8-naphthalic acid, affording three new binary molecular organic salts of [(C 3 H 5 N 2 + )·(C 7 H 5 O 4 )] (1), [(C 3 H 5 N 2 + )·(C 7 H 4 O 3 Cl )] C 7 H 5 O 3 Cl (2), and [(C 3 H 5 N 2 + ) (C 12 H 7 O 4 )] (3). Proton transfer occurs from the COOH of carboxylic acid to nitrogen of imidazole in all complexes (1-3), leading to the hydrogen bond N-H…O in all structures. To our knowledge, the recognition pattern between the carboxylic acid group and imidazole (acid-imidazole synthon) is less well-studied so far. The cooperation among COOH, COO and imidazolium cation functional groups for the observed hydrogen bond synthons is examined in the three structures. Generally, the strong N-H…O and O-H…O hydrogen bonds define supramolecular architecture and connectivity within chains, while weaker C-H…O hydrogen bonds play the dominant role in controlling the interactions between layers in these novel organic salts. Thermal stability of these compounds has been investigated by thermogravimetric analysis (TGA) of mass loss.     

Carbon Dioxide Capture and Utilization with Isomeric Forms of Bis(amino)-Tagged Zinc Bipyrazolate Metal–Organic Frameworks

Aiming at extending the tagged zinc bipyrazolate metal–organic frameworks (MOFs) family, the ligand 3,3’-diamino-4,4’-bipyrazole ( 3,3’-H₂L ) has been synthesized in good yield. The reaction with zinc(II) acetate hydrate led to the related MOF Zn(3,3’-L) . The compound is isostructural with its mono(amino) analogue Zn(BPZNH₂) and with Zn(3,5-L) , its isomeric parent built with 3,5-diamino-4,4’-bipyrazole. The textural analysis has unveiled its micro-/mesoporous nature, with a BET area of 463 m² g⁻¹. Its CO₂ adsorption capacity (17.4 wt. % CO₂ at p_CO2 = 1 bar and T = 298 K) and isosteric heat of adsorption (Q_st = 24.8 kJ mol⁻¹) are comparable to that of Zn(3,5-L) . Both Zn(3,3’-L) and Zn(3,5-L) have been tested as heterogeneous catalysts in the reaction of CO₂ with the epoxides epichlorohydrin and epibromohydrin to give the corresponding cyclic carbonates at T = 393 K and p_CO2 = 5 bar under solvent- and co-catalyst-free conditions. In general, the conversions recorded are higher than those found for Zn(BPZNH₂), proving that the insertion of an extra amino tag in the pores is beneficial for the epoxidation catalysis. The best catalytic match has been observed for the Zn(3,5-L) /epichlorohydrin couple, with 64 % conversion and a TOF of 5.3 mmol(carbonate) (mmol_Zn)⁻¹ h⁻¹. To gain better insights on the MOF-epoxide interaction, the crystal structure of the [epibromohydrin@ Zn(3,3’-L) ] adduct has been solved, confirming the existence of Br⋅⋅⋅(H)−N non-bonding interactions. To our knowledge, this study represents the first structural determination of a [epibromohydrin@MOF] adduct.     

A supramolecular organic framework with ant topology featuring interdigitation and interpenetration

H₄BOPTC reacts with IMI to yield a supramolecular organic framework, formulated as [IMIH⁺]₂√[H₂BOPTC^2 ? ]√0.5H₂O (1) (IMI = imidazole, H₄BOPTC = benzophenone-3,3′,4,4′-tetracarboxylic acid). Single-crystal X-ray diffraction analysis reveals that 1 shows a novel architecture with two-level hierarchical entanglement. H₂BOPTC^2 ?  connects to IMIH⁺ through hydrogen bonds, providing 1D ribbon. The basic ribbons are entangled into a 3D net with ant topology. Then the ant nets further interpenetrate to give the final entangled framework. The thermal stability, optical band gap energy and photoluminescent property of 1 have also been investigated.     

Molecular Encapsulation of Trimeric Chromium Carboxylate Clusters in Metal–Organic Frameworks and Propylene Sorption

Oxo-bridged trimeric chromium acetate clusters [Cr₃O(OOCCH₃)₆(H₂O)₃]NO₃ have been encapsulated for the first time in the mesoporous cages of the chromium terephthalate MIL-101(Cr). The isolated clusters in MIL-101(Cr) have increased affinity towards propylene compared to propane, due to generation of a new kind of pocket-based propylene-binding site, as supported by DFT calculations.     

Dynamic Coordination Chemistry of Fluorinated Zr-MOFs: Synthetic Control and Reassembly/Disassembly Beyond de Novo Synthesis to Tune the Structure and Property

Known for excellent stability, porosity and functionality, the high-valent Zr⁴⁺ metal–organic frameworks (Zr-MOFs) still meets synthetic challenge in modulating the strength of Zr-O_carboxylate linkage. Herein we explore the unusual coordination dynamics of fluorinated Zr-MOFs by designing two trifluoromethyl modified ligands with distinct geometry preference to form a family of thermodynamic and kinetic products. The low-connecting kinetic Zr-MOFs possess substitutable coordination sites to endow Zr₆-cluster with extra dynamic behaviors, thus opening a post-synthetic pathway to sequential reassembly/disassembly processes. Comprehensive factors, including ligand geometry, Zr₆-cluster connectivity, acid modulator and reaction temperature/concentration, have been studied for controllable syntheses. The stability, hydrophobicity and gas adsorption/separation properties of obtained Zr-MOFs are explored. This work sheds light on the understanding of the dynamic coordination chemistry of Zr-MOFs beyond strong Zr−O bond, which poses a versatile platform for modification and functionalization of Zr-MOFs.     

Porous Cationic Covalent Triazine‐Based Frameworks as Platforms for Efficient CO2 and Iodine Capture

Porous cationic covalent triazine‐based frameworks (CTFs) with imidazolium salts as tectons were prepared via ionothermal synthesis. The high‐PF₆^?‐content CTF shows the CO₂ adsorption of 44.7 cm³ g^?1 and I₂ capture capacity of 312 wt %. The influence of counterion species and contents on the porosities, CO₂ adsorptions, and I₂ capture capacities of the CTFs has been investigated.     

A 3D Polyoxometalate‐Based Framework Constructed from Ag/trz Metal‐Organic Ribbons and P2W18 Polyoxoanions: Synthesis,Structure and Electrochemical Properties

A Wells‐Dawson Polyoxometalate‐based hybrid, Ag₉(trz)₃(Htrz)₄ (H₂O)(P₂W₁₈O₆₂)·3H₂O ( 1 ) (Htrz = 1,2,4‐1H‐triazole) was hydrothermally synthesized through using trz ligand and silver nitrate in the presence of [P₂W₁₈O₆₂]^6– polyoxoanion. In the 3D framework structure of compound 1 , two kinds of wave‐like Ag/trz chains originated from trz ligands and silver cations are aggregated in a “2+1” mode by {Ag₂/trz} linkages to result in a 1D Ag/trz metal‐organic ribbon, which is further extended into a 3D framework structure by [P₂W₁₈O₆₂]^6– polyoxoanions through Ag‐O covalent bonds. Additionally, the electrochemical properties of compound 1 have also been investigated.