Interaction between ions and substituted buckybowls: A comprehensive computational study

Complexes formed by substituted buckybowls derived from corannulene and sumanene with sodium cation or chloride anion have been computationally studied by using a variety of methods. Best results have been obtained with the SCS‐MP2 method extrapolated to basis set limit, which reproduces the highest‐level values obtained with the MP2.X method. All bowls form stable complexes with chloride anion, with stabilities ranging from ?6 kcal/mol in the methylated corannulene derivative to ?45 kcal/mol in the CN‐substituted sumanene. The opposite trend is observed in sodium complexes, going from deeply attractive complexes with the methylated derivatives (?36 kcal/mol with sumanene derivative) to slightly repulsive ones in the CN‐substituted bowls (2 kcal/mol in the corannulene derivative). Anion complexes are stabilized by large electrostatic interactions combined with smaller though significant dispersion and induction contributions. Conversely, cation complexes are stabilized by large induction contributions capable of holding together the bowl and the cation even in cases where the electrostatic interaction is repulsive. The effect of substitution is mainly reflected on changes in the molecular electrostatic potential of the bowl and, thus, in the electrostatic contribution to the interaction. Therefore, the variations in the stability of the complexes on substitution could be roughly predicted just considering the changes in the electrostatic interaction. However, other contributions also register changes mainly as a consequence of displacements on the position of the ion at the minimum, so the accurate prediction of the stability of this kind of complexes requires going further than the electrostatic approach. © 2014 Wiley Periodicals, Inc.     

荧光自旋捕获探针的合成及ESR捕获研究

设计合成了具有荧光基团的新型硝酮类自由基捕获探针并对其结构进行了表征.自由基捕获实验结果表明,该探针能实现对超氧阴离子自由基与碳中心自由基的捕获.此外,该自由基捕获探针反应产物的荧光强度与被捕获自由基浓度之间存在相关性,有望建立依据荧光强度分析被捕获自由基浓度的新方法.     

New dicationic piperidinium hexafluorophosphate ILs,synthesis, characterization and dielectric measurements

A new class of dicationic ionic liquids (ILs) were synthesized for electrochemical applications at high temperatures. The syntheses are based on a dialkylation reaction of N-alkylpiperidine followed by anion exchange. The structures of ILs, based on piperidinium combined with hexafluorophosphate anion, were identified by using ¹H, ¹³C, ¹⁹F, ³¹P NMR and FT-IR spectroscopy. ILs’ thermal properties were investigated in the temperature range from −50 to 350 °C by using differential scanning calorimetry (DSC). In the frequency of 10⁻²–10⁶ Hz range, dielectric measurements were performed on ILs’ samples at various temperatures from −80 to 20 °C, i.e. around the glass transition temperature. The peak relaxation was observed near to this temperature. Also, the conductivity was investigated and the energy activation determined. The temperature dependence of the relaxation times was shown to be governed by the Arrhenius equation.     

Thiourea- and Amino-Substituted Benzoxadiazole Dyes with Large Stokes Shifts as Red-Emitting Probe Monomers for Imprinted Polymer Layers Targeting Carboxylate-Containing Antibiotics

Bifunctional fluorescent molecular oxoanion probes based on the benzoxadiazole (BD) chromophore are described which integrate a thiourea binding motif and a polymerizable 2-aminoethyl methacrylate unit in the 4,7-positions of the BD core. Concerted charge transfer in this electron donor-acceptor-donor architecture endows the dyes with strongly Stokes shifted (up to >250 nm) absorption and fluorescence. Binding of electron-rich carboxylate guests at the thiourea receptor leads to further analyte-induced red-shifts of the emission, shifting the fluorescence maximum of the complexes to ≥700 nm. Association constants for acetate are ranging from 1–5×10⁵ M⁻¹ in acetonitrile. Integration of one of the fluorescent probes through its polymerizable moiety into molecularly imprinted polymers (MIPs) grafted from the surface of submicron silica cores yielded fluorescent MIP-coated particle probes for the selective detection of antibiotics containing aliphatic carboxylate groups such as enoxacin (ENOX) at micromolar concentrations in highly polar solvents like acetonitrile.     

Direct Comparison of Subvalent,Polycationic Group 13 Cluster Compounds: Lessons learned on Isoelectronic DMPE Substituted Gallium and Indium Tetracation Salts

The tetracationic, univalent cluster compounds [{M(dmpe)}₄]⁴⁺ (M=Ga, In; dmpe=bis(dimethylphosphino)ethane) were synthesized as their pf salts ([pf]⁻=[Al(OR^F)₄]⁻; R^F=C(CF₃)₃). The four-membered ring in [{M(dmpe)}₄]⁴⁺ is slightly puckered for M=Ga and almost square planar for M=In. Yet, although structurally similar, only the gallium cluster is prevalent in solution, while the indium cluster forms temperature dependent equilibria that include even the monomeric cation [In(dmpe)]⁺. This system is the first report of one and the same ligand inducing formation of isoelectronic and isostructural gallium/indium cluster cations. The system allows to study systematically analogies and differences with thermodynamic considerations and bonding analyses, but also to outline perspectives for bond activation using cationic, subvalent group 13 clusters.     

Carbazole-Based Colorimetric Anion Sensors

Owing to their strong carbazole chromophore and fluorophore, as well as to their powerful and convergent hydrogen bond donors, 1,8-diaminocarbazoles are amongst the most attractive and synthetically versatile building blocks for the construction of anion receptors, sensors, and transporters. Aiming to develop carbazole-based colorimetric anion sensors, herein we describe the synthesis of 1,8-diaminocarbazoles substituted with strongly electron-withdrawing substituents, i.e., 3,6-dicyano and 3,6-dinitro. Both of these precursors were subsequently converted into model diamide receptors. Anion binding studies revealed that the new receptors exhibited significantly enhanced anion affinities, but also significantly increased acidities. We also found that rear substitution of 1,8-diamidocarbazole with two nitro groups shifted its absorption spectrum into the visible region and converted the receptor into a colorimetric anion sensor. The new sensor displayed vivid color and fluorescence changes upon addition of basic anions in wet dimethyl sulfoxide, but it was poorly selective; because of its enhanced acidity, the dominant receptor-anion interaction for most anions was proton transfer and, accordingly, similar changes in color were observed for all basic anions. The highly acidic and strongly binding receptors developed in this study may be applicable in organocatalysis or in pH-switchable anion transport through lipophilic membranes.     

Terpyridine-Functionalized Calixarenes: Synthesis,Characterization and Anion Sensing Applications

Lanthanide complexes have been developed and are reported herein. These complexes were derived from a terpyridine-functionalized calix[4]arene ligand, chelated with Tb³⁺ and Eu³⁺. Synthesis of these complexes was achieved in two steps from a calix[4]arene derivative: (1) amide coupling of a calix[4]arene bearing carboxylic acid functionalities and (2) metallation with a lanthanide triflate salt. The ligand and its complexes were characterized by NMR (¹H and ¹³C), fluorescence and UV-vis spectroscopy as well as MS. The photophysical properties of these complexes were studied; high molar absorptivity values, modest quantum yields and luminescence lifetimes on the ms timescale were obtained. Anion binding results in a change in the photophysical properties of the complexes. The anion sensing ability of the Tb(III) complex was evaluated via visual detection, UV-vis and fluorescence studies. The sensor was found to be responsive towards a variety of anions, and large binding constants were obtained for the coordination of anions to the sensor.     

Boron- versus Nitrogen-Centered Nucleophilic Reactivity of (Cyano)hydroboryl Anions: Synthesis of Cyano(hydro)organoboranes and 2-Aza-1,4-diborabutatrienes

Cyclic alkyl(amino)carbene-stabilized (cyano)hydroboryl anions were synthesized by deprotonation of (cyano)dihydroborane precursors. While they display boron-centered nucleophilic reactivity towards organohalides, generating fully unsymmetrically substituted cyano(hydro)organoboranes, they show cyano-nitrogen-centered nucleophilic reactivity towards haloboranes, resulting in the formation of hitherto unknown linear 2-aza-1,4-diborabutatrienes.     

Cationic Organophosphorus Chromophores: A Diamond in the Rough among Ionic Dyes

Tunable electron-accepting properties of the cationic phosphorus center, its geometry and unique preparative chemistry that allows combining this unit with diversity of π-conjugated motifs, define the appealing photophysical and electrochemical characteristics of organophosphorus ionic chromophores. This Minireview summarizes the achievements in the synthesis of the π-extended molecules functionalized with P-cationic fragments, modulation of their properties by means of structural modification, and emphasizes the important effect of cation-anion interactions, which can drastically change physical behavior of these two-component systems.     

Halogen-Bonding Strapped Porphyrin BODIPY Rotaxanes for Dual Optical and Electrochemical Anion Sensing

Anion receptors employing two distinct sensory mechanisms are rare. Herein, we report the first examples of halogen-bonding porphyrin BODIPY [2]rotaxanes capable of both fluorescent and redox electrochemical sensing of anions. ¹H NMR, UV/visible and electrochemical studies revealed rotaxane axle triazole group coordination to the zinc(II) metalloporphyrin-containing macrocycle component, serves to preorganise the rotaxane binding cavity and dramatically enhances anion binding affinities. Mechanically bonded, integrated-axle BODIPY and macrocycle strapped metalloporphyrin motifs enable the anion recognition event to be sensed by the significant quenching of the BODIPY fluorophore and cathodic perturbations of the metalloporphyrin P/P^+. redox couple.