Synthesis of sterically hindered antipyrines for intramolecular charge transfer facilitated sensing

A new series of sterically hindered antipyrine derivatives have been synthesized by Schiff base condensation for potential fluorescence sensing applications. Their optical, thermal, and electrochemical properties were fully characterized. Broad absorption spectra were observed as a result of the strong intramolecular charge transfer between antipyrine and sterically hindered conjugated moiety. Reversible one electron oxidation couple was observed for most compounds, with carbazole, phenothiazine, and bithiophene functionalized derivatives exhibiting extra reversible one one-electron oxidation process at higher positive potentials. Cabazole functionalized antipyrine derivative APCZ presents good fluorescence sensing for Co2+ and Cu2+, with 3.41-fold enhancement in fluorescence intensity and 2-fold enhancement in fluorescence quantum yield observed. Copyright (c) 2012 John Wiley & Sons, Ltd.