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The preparation and sensing properties of a tetracyclic cyclophane receptor containing two imidazolium rings as anion binding sites and two fluorene rings as fluorescent signaling units, are reported. The receptor behaves as a selective fluorescent chemosensor molecule for inorganic phosphates. ¹H‐NMR spectroscopical data clearly indicate the simul...
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In this computational work, we propose to use the NMR chemical shift difference of NH2 protons for 1:1 complexes formed by aniline and nitrogen-containing proton acceptors for the estimation of the hydrogen bond energy and geometry (N⋯H and N⋯N distances). The proposed correlations could be applied to other aromatic amines as well, in a gas phase,...
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... [9] They also described a tetracyclic cyclophane receptor containing two imidazolium rings which can capture single and dimeric phosphates and PF 6 À . [10] The same group has also reported capturing of dimers of anionic phosphonates and oxyacids by cyanostar macrocycles. [11] Anion-anion interaction has also been reported in perrhenate, pertechnetate and permanganate anions. ...
Formation of a genuine chemical bond between two similarly charged fragments is beyond expectation. Any such interaction generally lies in the realm of non‐covalent interaction. Herein, formation of a strong dative covalent bond between two anionic fragments is reported for the first time. Calculation using ab initio coupled cluster theory reveals the formation of an unprecedented strong H3Be⁻←X⁻ (X⁻=CH3⁻, CN⁻, OH⁻, F⁻) dative covalent bond. The calculated bond dissociation energies in polar solvents are significant, which indicates the possibility of their experimental realization.
With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host-guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes-in particular, fluorescent cyclophanes, having rich structural characteristics and functions-have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host-guest chemistry and applications related to their structure and properties are highlighted.
Anion detection and quantification remain always challenging due to their inherent strong hydration energy, complex geometries and pH dependence. Several techniques and methodologies have been developed for the recognition and sensing of anions. Among all such techniques, fluorescence spectroscopy has received special attention due to its highly convenient and accurate detection capacity. A number of different mechanisms are prevalent in the literature for the emission spectroscopy. Intramolecular charge transfer (ICT) is one of such predominant mechanisms, which is usually observed in molecules with D-π-A or D-A type of structural arrangement. When ICT based probes interact with the desired analyte, the electron density in the recognition group is altered (e.g., as a result of bond cleavage, substitution, or substrate coordination) which installs a ‘push-pull’ system in the molecule. In the past two decades, a huge number of publications have emerged on this topic. Keeping into account the vast number of reports on anion sensing relied upon ICT mechanism, we will confine our discussion to sensors that are developed in last 6 years. The structural features of all the selected probes (total 123 probes), developed in the last 6 years, will be discussed in the present review with the particular emphasis on the mechanism (ICT) responsible for the detection and recognition of various anions. Apart from the mechanistic details, information about the detection limit, selectivity and visible change of color/state, binding units and stoichiometries with anions have also been discussed thoroughly and collected in tabular format. For the sake of legibility, all the probes have been categorized according to the number of anions they detect and are subdivided into specific anion-based sensing and their mechanism. This review aims to be a comprehensive, convincing and reader-friendly review of general interest to the chemistry community. To the best of our knowledge, this is the first survey in the contemporary time to cover the complete literature of past six years about anion sensing exclusively based on ICT mechanism. Throughout the review we provide an illustrative overview about the design strategies that may be exploited for analyte sensing and their corresponding suitable molecular systems. We hope, this review will enhance the basic understanding of the subject of ICT based mechanism which will certainly help the researchers to generate new molecular architectures with superior anion sensing ability in future.
To develop fluorophore-labelled pyridinium-based macromolecular architectures for fluorometric and colorimetric detection of anions, two polymers P1 and P2 are synthesized. Linear polymer P1 and cross-linked polymer P2, prepared from N-methacryloyl-3-aminopyridine monomers via free radical polymerization followed by quaternization of the pyridine ring nitrogen with anthracene as a fluorescent marker, have been successfully employed in anion sensing. P1 exhibits excellent sensing of HPPi in aqueous DMSO. In addition to the enhancement of fluorescence emission of the anthracene moiety, P1 exclusively shows excimer/exciplex emission in the presence of HPPi over other anions and exhibits selectivity to HPPi with a detection limit of about 1.63 ppm. Cross-linked P2 exhibits naked-eye detection of PPi/HPPi over other anions studied via indicator displacement assay (IDA).
Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010–2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA.
Interanionic H-bonds (IAHBs) are unfavourable interactions in the gas phase becoming favoured when anions are in solution. Dianion dimers are also susceptible to be trapped inside the cavities of cyanostar (CS) macrocycles, thus, the formation of 2:2 anion:cyanostar aggregates are mainly supported by three kind of interactions: IAHBs between the dianions, π-π stacking between the confronted cyanostars, and the presence of an intricate network of multiple C(sp²)H···O H-bonds between cyanostar ligands and the anionic moieties. An analysis of the interaction energies supportted by NBO reveals a slight cooperative effect of the CSs in the IAHBs stabilisation.
A Conceptual DFT study of the dissociation of anionic and neutral phosphonate dimers has been carried out. In addition, the dianion complexes have been studied in the presence of two solvents, water and tetrahydrofuran. The dissociation of the dianion complexes in the gas phase and in solution present a maximum along the reaction coordinate that is not present in the neutral-neutral and anion-neutral complexes. The principal chemical descriptors (chemical potential, reaction electronic flux, hardness and global electrophilicity index) do not show changes in their trends along the dissociation profiles even when there is an energy maximum in the case of the anion-anion complexes.
We describe here the utilization of 1,4-Naphthoquinone and 3-iodo-1,4-Naphthoquinone motif as new anion binding sites by hydrogen-or halogen-bonding interactions respectively. These binding sites have been integrated in bidentate ester based receptors. Emission experiments reveals that both receptors recognize selectively sulfate anion, which induced a remarkable increase of a new emission band attributed to the formation of π-stacking interactions between two 1,4-naphthoquinone units. Absorption spectroscopy and mass spectrometry indicate the disruption of the ester group of the 1,4-naphthoquinone based receptor with the presence of HP 2 O 7 3-, H 2 PO 4-, F-, AcO-and C 6 H 5 CO 2-and in the halogenated receptor with HP 2 O 7 3-, F-and AcO-anions, while the presence of sulfate anion showed the clasical complexation behaviour. 1 H-NMR experiment shows a slow exchange process of the receptors with their sulfate complexes. The binding mode of the receptors with sulfate has been studied by DFT calculations along with the Molecular Electrostatic Potential (MEP) surface computational tool that reveals those parts of the receptors more suitable for interacting with anions.
