A comparative study of two thienopyrimidine Schiff base probes for sequential monitoring of Ga3+ and Pd2

Abstract

Two Schiff base probes (S1 and S2) were prepared and synthesized by incorporating thienopyrimidine into salicylaldehyde or 3-ethoxysalicylaldehyde individually, with the aim of detecting Ga³⁺ and Pd²⁺ sequentially. Upon chelation with Ga³⁺, S1 and S2 exhibited fluorescence enhancement in DMSO/H₂O buffer. Both S1-Ga³⁺ and S2-Ga³⁺ were quenched by Pd²⁺. The limit of detection for S1 in response to Ga³⁺ and Pd²⁺ was 2.86 × 10^-7 and 4.4 × 10^-9 M, respectively. For S2, the limit of detection for Ga³⁺ and Pd²⁺ was 4.15 × 10^-8 and 3.0 × 10^-9 M, respectively. Furthermore, the complexation ratios of both S1 and S2 with Ga³⁺ and Pd²⁺ were determined to be 1:2 through Job's plots, ESI-MS analysis, and theoretical calculations. Two molecular logic gates were constructed, leveraging the response behaviors of S1 and S2. Moreover, the potential utility of S1 and S2 for monitoring Ga³⁺ and Pd²⁺ in domestic water was verified.

Keywords: Schiff base; fluorescence probe; gallium; palladium; thienopyrimidine.