Anion-Binding Properties of the Tripyrrolemethane Group: A Combined Experimental and Theoretical Study (original) (raw)
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The association constants of the complexes formed by two hosts containing pyrrole, amide and azine (pyridine and 1,8-naphthyridine) groups and six guests, all monoanions (Cl-, CH3CO2-, NO3-, H2PO4-, BF4-, PF6-), have been determined using NMR titrations. The X-ray crystal structure of the host N2,N5-bis(6-methylpyridin-2-yl)-3,4-diphenyl-1H-pyrrole- 2,5-dicarboxamide (1) has been solved (P21/c monoclinic space group). B3LYP/6-31G(d,p) and calculations were carried out in an attempt to rationalize the trends observed in the experimental association constants.
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Tetrahedron, 2007
We report on the synthesis and characterization of novel shape-persistent, optically active arylamide macrocycles, which can be obtained using a one-pot methodology. Resolved, axially chiral binol scaffolds, which incorporate either methoxy or acetoxy functionalities in the 2,2' positions and carboxylic functionalities in the external 3,3' positions, were used as the source of chirality. Two of these binaphthyls are joined through amidation reactions using rigid diaryl amines of differing shapes, to give homochiral tetraamidic macrocycles. The recognition properties of these supramolecular receptors have been analyzed, and the results indicate a modulation of binding affinities towards dicarboxylate anions, with a drastic change of binding mode depending on the steric and electronic features of the functional groups in the 2,2' positions.
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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
Chemical Science, 2012
General and synthetic procedures 1 H NMR spectrum of 3 in DMSO-d 6 . 13 C NMR spectrum of 3 in DMSO-d 6 . MALDI-TOF mass spectrum of 3. 1 H NMR spectrum of 4 in CDCl 3 . 13 C NMR spectrum of 4 in CDCl 3 . MALDI-TOF mass spectrum of 4. 1 H NMR spectrum of 5 in CD 3 CN. 13 C NMR spectrum of 5 in CD 3 CN. MALDI-TOF mass spectrum of 5. 1 H NMR spectrum of 1 in CD 3 CN. Figure S11 13 C NMR spectrum of 1 in CD 3 CN. Figure S12 MALDI-TOF mass spectrum of 1. Figure S13 Comparison of partial 1 H NMR spectra of 4, 5 and 1 in CD 3 CN. Anion binding studies Figure S14 Recovery of fluorescence of [1•2 -] upon titration with HP 2 O 7 3-(as the tetrabutylammonium salt) in acetonitrile at ex = 410 nm.
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.
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.
Journal of Structural Chemistry, 2015
Sterically hindered meso-tetramethyl-meso-tetraarylcalix[4]pyrroles 1-4 where aryl is p-fluorophenyl 1, p-chlorophenyl 2, and p-methylphenyl 3, 4 (configurational isomers) are synthesized and purified by the recrystallization technique. They are characterized by IR, 1 H and 13 C NMR, and mass spectroscopy. Configurational isomers DDEE (3) and DDDD (4) of meso-tetramethylmeso-tetramethylphenylcalix[4]pyrroles are assigned by the 1 H NMR studies and confirmed by the X-ray diffraction analysis. The single crystal X-ray diffraction analysis reveals that the ethanol adduct of 1, the acetone adduct of 2 and 3 adopt the 1,2-conformation while the acetone-water adduct of 1 and the acetone adduct of 4 adopt partial cone and cone conformations respectively. The conformational diversity is due to non-covalent interactions among the encapsulated guest, pyrrolic NH protons, and meso-substituents. Anion binding studies (F-, Cl-, CH 3 COO-, 4 HSO) are carried out through 1 H NMR titrations; the binding constants are evaluated using the EQNMR program, displaying that they are more selective towards fluoride rather than other anions with the 1:1 stoichiometry. The configuration of compounds drastically influences the ion-recognition processes.