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Highly Selective Optical‐Sensing Membranes, Containing Calix[4]arene Chromoionophores, for Pb 2+ Ions
Author(s) -
van der Veen Niels J.,
Rozniecka Ewa,
Woldering Léon A.,
Chudy Michal,
Huskens Jurriaan,
van Veggel Frank C. J. M.,
Reinhoudt David N.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011119)7:22<4878::aid-chem4878>3.0.co;2-8
Subject(s) - bathochromic shift , chemistry , hypsochromic shift , deprotonation , metal ions in aqueous solution , inorganic chemistry , ion , alkali metal , membrane , qualitative inorganic analysis , selectivity , protonation , metal , photochemistry , organic chemistry , fluorescence , biochemistry , physics , quantum mechanics , catalysis
Plasticized poly(vinyl chloride) (PVC) optode membranes containing novel calix[4]arene chromoionophores 1 or 2 and one equivalent of a lipophilic anion respond to Pb 2+ ions with high selectivity over alkali, alkaline‐earth, and other heavy metal ions. This selectivity stems from the combination of ligand specificity and a unique ion exchange scheme that employs both monovalent metal ions and protons as the exchanged ions. Complexation of Pb 2+ ions inside the membrane is accompanied by deprotonation of the chromoionophores, which causes a bathochromic shift of the absorption maximum λ max . The response to Pb 2+ ions is modulated by pH and alkali metal ions in a fashion that is consistent with the proposed ion‐exchange mechanism. Of all of the other metal ions tested, only Cs + and Ag + produce a color change. However, these monovalent metal ions cause hypsochromic shifts of λ max instead of the bathochromic shift caused by Pb 2+ , because the chromoionophores remain protonated upon complexation.