Synthesis, structure, anion binding, and sensing by calix [4] pyrrole isomers

R Nishiyabu, MA Palacios, W Dehaen… - Journal of the …, 2006 - ACS Publications
Journal of the American Chemical Society, 2006ACS Publications
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 α '-and β-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 …
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 α‘- and β-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 β-pyrrole C−H of the inverted pyrrole moiety participates in the hydrogen-bonded anion−NC-OMCP complex. Preliminary colorimetric microassays using synthesized chromogenic calixpyrroles embedded in partially hydrophilic polyurethane matrices allow for observation of analyte-specific changes in color when the anions are administered in the form of their aqueous solutions and in the presence of weakly competing anions.
ACS Publications
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