Highly sensitive and selective chemosensors for Cu2+ and Al3+ based on photoinduced electron transfer (PET) mechanism

Abstract

Two novel acridine based chemosensors 7a and 7b were synthesized and configured as “fluorophore–spacer–receptor” systems based on photoinduced electron transfer. The probes 7a and 7b exhibited high selectivity and sensitivity for the detection of Cu²⁺ and Al³⁺ respectively over commonly coexistent metal ions in CH₃CN. The binding association constants (K_a) of 7a–Cu²⁺ and 7b–Al³⁺ were found to be 4.0 × 10⁴ M⁻¹ and 1.7 × 10⁴ M⁻¹ in CH₃CN, and the corresponding detection limits were calculated to be 2.8 × 10⁻⁷ M and 5.8 × 10⁻⁷ M, respectively. The fluorescence response of 7a–Cu²⁺ and 7b–Al³⁺ with respect to pH change was studied and the resulting demonstrated fluorescence enhancement was observed in the pH range of 7.0–9.0. The chromophores were characterized by FT-IR, ¹H-NMR, ¹³C-NMR and HR Mass spectral analysis.