Fluorescence Regeneration as a Signaling Principle for Choline and Carnitine Binding: A Refined Supramolecular Sensor System Based on a Fluorescent Azoalkane

• Published in: Advanced functional materials Vol. 16; no. 2; pp. 237 - 242
• Main Authors: Bakirci, H., Nau, W. M.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 19.01.2006; WILEY‐VCH Verlag
• Subjects: Azoalkanes; Biosensors; Fluorescence; Host-guest systems; Sensors; Supramolecular materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200500219

The fluorescent azoalkane, 2,3‐diazabicyclo[2.2.2]oct‐2‐ene (DBO), forms inclusion complexes with p‐sulfonatocalix[4]arene (CX4). The binding constants are on the order of 103 M–1 in water. The addition of CX4 to DBO solutions results in an efficient fluorescence quenching (up to 90 %). This supramolecular system can be used as a truly water‐soluble sensor system to signal the binding of organic ammonium ions over a large pH range. Addition of choline and carnitine derivatives and tetraalkylammonium ions results in regeneration of this fluorescence, from which the binding constants (KC = 103–105 M–1) are calculated by means of a competitive complexation model. Electrostatic effects are observed, namely, a more‐than‐one order of magnitude weaker binding of the carnitines in neutral solution. A truly water‐soluble choline and carnitine recognition fluorescent sensor system with improved fluorescence enhancement is based on the formation of an inclusion complex (see Figure) between an azoalkane, as a competitively bound fluorescent guest, and a water‐soluble calixarene as host with cation‐receptor properties. DBO: 2,3‐diazabicyclo[2.2.2]oct‐2‐ene.