SYNTHESIS OF FERROCENE DERIVATIVES CONTAINING VARIOUS RECEPTORS AS CYANIDE ION SENSORS

Abstract

The goal of this research is to design and synthesize molecular sensor for cyanide anion. The signalling unit and receptor unit were connected through aryl ethyne moiety by using Sonogashira-cross coupling. The unsymmetrically ferrocene derivatives containing boronic acid and 2, 2-dipicolylamine (DPA) as receptor unit, L1 and L2, were obtained in moderate yields, 45% and 67%, respectively. Cyclic voltammetry of L1 in 0.1 M TBAPF6 in CH3CN exhibited high selectivity toward cyanide ions in the presence of various anions. In addition, the binding of cyanide at the boron center of L1 was supported by 1H NMR titrations of L1 and cyanide ions in CD3OD. The cyclic voltammetry studies of L2 with various metal ions in 0.1 M TBAPF6 in CH3CN exhibited high selectivity toward Cu2+ ion. The cyclic voltammogram of L2-Cu2+ showed the shift of the redox potential of ferrocene and a reversible redox wave of CuII/CuI. The blue-shift of absorption spectrum from 310 to 260 nm in UV-Vis spectrum of L2 upon addition of Cu2+ supported the result from cyclic voltammetry. In the presence of CN-, H2PO4- and F-, the UV-Vis spectrum of L2-Cu2+ exhibited a red shift of the absorption band from 260 to 310 nm. Using cyclic voltammetry, the addition of CN- or F- to the solution of L2-Cu2+ complex in 0.1 M TBAPF6 in CH3CN did not show any potential shift of the Fc/Fc+ redox couple. In addition, the reversible wave of CuII/CuI redox couple disappeared, indicating that CN- and F- interacted at the copper (II) center of L2-Cu2+ complex. Addition of H2PO4- to the solution of L2-Cu2+ complex resulted in the precipitation. Therefore, L2-Cu2+ complex cannot be used for detection of H2PO4- by cyclic voltammetry.