The first colorimetric receptor for the B4O72− anion based on nitro substituted phenanthroimidazole ferrocene derivatives

Abstract

Four phenanthroimidazole ferrocene derivatives (2a–2d) were designed, synthesized and characterized by ¹H NMR, ¹³C NMR and high-resolution mass spectroscopy (HRMS). Recognition of 12 anions by 2a–2d was investigated by UV-Vis absorption analysis, showing that 2b and 2d sensed B₄O₇²⁻ selectively among the tested anions with an obvious color change observed. ¹H NMR titrations and theoretical calculations demonstrated that 2b binds B₄O₇²⁻ through O⋯H hydrogen bonding and O⋯B interactions between the nitro moiety and the B₄O₇²⁻ anion.