Colorimetric Sensing of Fluoride Ion by New Expanded Calix[4]pyrrole through Anion (original) (raw)
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Organic Letters
Two new expanded calix[4]pyrroles 3 and 4 were synthesized by '2 þ 2' cyclocoupling of easily prepared diboryldipyrromethane 7 (by Ir-catalyzed CH-bond activation) with appropriate diiodoarenes using the Suzuki protocol. Owing to the unique design, both macrocycles exhibited extended π-conjugation and enhanced fluorescence. Upon complexation with anions (fluoride and acetate), receptor 3 displayed turn-on sensing of fluorescence, whereas 4 showed turn-off sensing.
Synthesis of pyrenylcalix[4]arene-calix[4]pyrrole as fluorogenic sensor for anion
Thesis (M.Sc.)--Chulalongkorn University, 2006 A fluorogenic sensor for anion, pyrenylcalix[4]arene-calix[4]pyrrole (7), was successfully synthesized and characterized by spectroscopic techniques. It was revealed that the conformations of calix[4]arene and calix[4]pyrrole of 7 are in cone and 1,3-alternate manners, respectively. The glycolic spacers are in trans-position. Anion complexation studies of ligand 7 were carried with tetrabutylammonium salts by fluorescence spectroscopy. The spectra of all complexes exhibited an increase of monomer fluorescence emission at wavelengths of 376 and 396 nm when excited at 343 nm by a PET-based mechanism. According to fluorescence titrations, fluorogenic sensor 7 formed complexes with high affinity to fluoride following by acetate, chloride, bromide, benzoate, ions with logK of 3.45, 3.25, 1.74, 1.62 and 1.28 respectively. An addition of excesses fluoride ion to a solution of 7 resulted in a color change of solution of 7 and fluorescence quenc...
Synthesis, Structure, Anion Binding, and Sensing by Calix[4]pyrrole Isomers
Journal of the American Chemical Society, 2006
The synthesis, structure, and anion binding properties of chromogenic octamethylcalix[4]pyrroles (OMCPs) and their N-confused octamethylcalix[4]pyrrole isomers (NC-OMCPs) containing an inverted pyrrole ring connected via R′-and -positions are described. X-ray diffraction analyses proved the structures of two synthesized isomeric pairs of OMCPs and NC-OMCPs. The addition of anions to solutions of chromogenic OMCPs and NC-OMCPs resulted in different colors suggesting different anion-binding behaviors. The chromogenic NC-OMCPs showed significantly stronger anion-induced color changes compared to the corresponding chromogenic OMCP, and the absorption spectroscopy titrations indicated that chromogenic OMCPs and NC-OMCPs also possess different anion binding selectivity. Detailed NMR studies revealed that this rather unusual feature stems from a different anion-binding mode in OMCPs and NC-OMCPs, one where the -pyrrole C-H of the inverted pyrrole moiety participates in the hydrogenbonded anion-NC-OMCP complex. Preliminary colorimetric microassays using synthesized chromogenic calixpyrroles embedded in partially hydrophilic polyurethane matrices allow for observation of analytespecific changes in color when the anions are administered in the form of their aqueous solutions and in the presence of weakly competing anions.
Anion Sensing by Fluorescent Expanded Calixpyrroles
Chemistry (Weinheim an der Bergstrasse, Germany), 2018
Expanded calixpyrrole-type macrocycles, calix[2]benzo[4]pyrroles, bearing fluorescent moieties attached via conjugated vinyl spacers, have been synthesized from the corresponding formyl derivatives through Knoevenagel condensation. The anion-binding properties of the resulting fluorescent macrocycles have been studied by means of NMR, UV/Vis, and fluorescence spectroscopies. Our main focus has been on dicarboxylates matching the size of the binding cavity of the calix[2]benzo[4]pyrrole skeleton. The observed anion-binding properties were compared with those of the regular calix[4]pyrroles bearing identical fluorophores. Surprisingly, the parent calix[4]pyrroles appear to be equally efficient, if not more so, for sensing anions such as dicarboxylates. Affinity constants determined for various anions and dianions show the sensors S1-S5 to be highly cross-reactive. The cross-reactivity of the sensors was utilized in a microchip-based array, which showed perfect (100 %) classification o...
Chromogenic anion molecular probes based on β,β’-disubstituted calix[4]pyrroles
Sensors and Actuators B: Chemical, 2014
The reaction of octamethylcalix[4]pyrrole with 3-(dimethylamino)prop-2-enal and POCl 3 affords a mixture of isomeric calix[4]pyrroles bearing two formylethenyl groups at the ˇ-pyrrolic positions. These dialdehydes were used in Knoevenagel reactions with malononitrile and indene-1,3-dione leading to new chromogenic anion molecular probes. The binding ability of the new receptors was investigated by UV-vis spectroscopy and NMR, indicating the formation of supramolecular 1:2 host:guest complexes with high affinity constants.
Coordination Chemistry Reviews, 2006
This is a first review devoted to N-confused calix[4]pyrroles (NCCPs). NCCPs are a relatively recent arrival to the family of the pyrrole-based anion binding macrocycles, being for the first time identified in 1999. Yet, in a relatively short time these calix[4]pyrrole (CP) isomers attracted attention of the community of research groups interested in anion binding and sensing. This is because they are relatively easy to synthesize, but mainly because they posses anion-binding properties that are different from that of regular calix[4]pyrroles. The difference in anion-binding properties stems from a different binding mode between the NCCP and anion. While the regular CPs adopt in the complex an ideal cone-like conformation where all four pyrroles-NHs engage in hydrogen bonding to the anion, the inverted pyrroles do not allow forming the cone. NCCPs bind anions via a confused cone (CC), by three NH hydrogen bonds with an anion and a CH-anion contact. This different binding mode results also in different anion-binding affinity and selectivity compared to regular CPs. Also, the inverted pyrroles offer a unique possibility for selective chemical modification of the receptor. The corresponding colorimetric sensors were tested for anion binding applications. The results of colorimetric assays for anions are presented and potential applications discussed.