Colorimetric Sensing of Fluoride Ion by New Expanded Calix[4]pyrrole through Anion (original) (raw)
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...
Anion Binding Studies of Fluorinated Expanded Calixpyrroles
The Journal of Organic Chemistry, 2005
The anion binding properties of fluorinated calix[n]pyrroles (n ) 4-6) in aprotic solvents (acetonitrile and DMSO) and modified reaction conditions allowing for the synthesis and isolation of the hitherto missing dodecafluorocalix[6]pyrrole from the condensation of 3,4-difluoro-1H-pyrrole and acetone are described. In acetonitrile solution containing 2% water, the association constants for the 1:1 binding interaction between octafluorocalix[4]pyrrole and chloride anion obtained with isothermal titration calorimetry (ITC) and 1 H NMR titration methods were found to match reasonably well. As compared to its nonfluorinated congener, octafluorocalix[4]pyrrole was found to display enhanced binding affinities for several representative anions in pure acetonitrile as judged from ITC analyses. Similar analyses of the fluorinated calix[n]pyrroles revealed an increase in the relative affinity for bromide over chloride with increasing macrocycle size, as manifest in a decrease in the binding ratio K a(Cl) /K a(Br) . Anion binding studies in the solid state, involving single-crystal X-ray diffraction analyses of the chloride and acetate anion complexes of octafluorocalix[4]pyrrole and decafluorocalix-[5]pyrrole, respectively, confirmed the expected hydrogen bond interactions between the pyrrolic NH protons and the bound anions.
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.
Industrial & Engineering Chemistry Research, 2000
The synthesis and chemical properties of a variety of chemically modified calix[4]pyrroles are described. The effects of structural changes, specifically the presence and absence of substituents on the meso-like and-pyrrolic carbons, on anion affinities are detailed as is their effect on macrocycle conformation. Also described are unsymmetrical systems, bearing an aliphatic and aromatic substituent on each of the four meso-like carbon atoms. In this case, the properties of the resulting configuration isomers are discussed in terms, again, of the resulting effects on macrocycle conformation and substrate binding affinity. Finally, the use of appropriately functionalized calix[4]pyrrole systems as rudimentary fluorescence-based anion sensors is presented.
Inversion of selectivity in anion recognition with conformationally blocked calix[4]pyrroles
Organic & Biomolecular Chemistry, 2012
Two calixpyrrole derivatives were synthesised. A p-dimethylaminobenzoyl group was electronically attached to a pyrrole ring, establishing an intramolecular hydrogen bond in a 1,3-alternate conformation. The formation of the H-bond was corroborated by IR, NMR, and X-ray measurements. NMR titration studies reveal that the H-bond is strong enough to block the conversion to a cone conformation, allowing them to only acquire a partial cone conformation. Affinity constants for several anions were calculated, and a noticeable increase was observed for tridentate tetrahedral anions, while the K a of spheric or bidentate anions decreased. In the presence of several acids, the synthesised compounds can act as chemosensors by a double process: protonation of the amino group and coordination of the generated anion. In addition, a displacement approach gives rise to a proof of concept for sulphonate recognition. † Electronic supplementary information (ESI) available: 1D and 2D NMR spectra of compounds 1 and 2. IR of 1, 2, 3 and 1·TBACl, NMR titration data, crystallographic data of compounds 1 and 2. CCDC 879852 (1) and 879855 (2). For ESI and crystallographic data in CIF or other electronic format see
Calix[4]arene-based ditopic receptors for simultaneous recognition of fluoride and cobalt(II) ions
Tetrahedron Letters, 2012
A series of calix[4]arene based ditopic receptors possessing bipyridyl and hydrazone units have been synthesized and evaluated for ionic recognition. It has been observed that the synthesized derivatives function as allosteric receptors for simultaneous recognition of Co 2+ and F À ions through non-covalent interactions. Significant bathochromic shifts in the UV-visible spectrum with a profound colour change promise their use to engineer novel applications.