Synthesis, optical and electrochemical properties of new receptors and sensors containing anthraquinone and benzimidazole units

Abstract

Novel anion receptors and sensors, HBIMANQ and BIMANQ fabricated from the imidazolole unit and anthraquinone moieties were synthesized. 1H NMR spectroscopy and UV–vis titrations in DMSO- d 6 and DMSO, respectively, showed that both receptors underwent deprotonation at the N H– moiety of the amide–anthraquinone unit in the presence of basic anions such as F − and AcO −. These phenomena gave a dramatic color change due to charge transfer transition corresponding to the shift of λ max from 371 nm to 489 nm. Redox chemistry of HBIMANQ and BIMANQ in the presence of anions (F −, Cl −, AcO −, BzO −, and H 2PO 4 −) using cyclic voltammetry showed the different CV responses upon addition of various anions. In the case of HBIMANQ with various anions, the CV changes are dependent on the basic strength of anions in order of F −>AcO −, BzO −>H 2PO 4 −>Cl −, Br −. Interestingly, the CV responses of BIMANQ with H 2PO 4 − exhibited the most significant changes. BIMANQ, thus, has an excellent electrochemical selectivity toward H 2PO 4 −.