Naphthalimide based smart sensor for CN−/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging

Abstract

Achieving selective detection of target analytes in aqueous media continues to be an arduous proposition. Herein, we report the conceptualization and synthesis of a novel tailor-fit molecular probe R based on 1,8-naphthalimide which acts as a trifunctional molecular sensor for CN⁻, Fe³⁺ and H₂S. R shows colorimetric and fluorometric “on–off” relay recognition for CN⁻ (red colour and orange emission) and Fe³⁺ (no colour and no emission) in 5% H₂O + DMSO medium which is experimentally ascertained to be a tandem deprotonation–protonation process and is supported by ¹H-NMR titration. Among all RSS (Reactive Sulphur Species), R shows selectivity for H₂S through red colouration. Other coexistent anions, cations and RSS cause no discernible perturbation to the detection process. The detection of H₂S is attributed to a chemodosimetric reduction of the nitro to amino group as evidenced by a potentiometric titration assay. The experimental observations are well supported by DFT theoretical calculation. The K_a for CN⁻/Fe³⁺ are 1.4 × 10⁴ M⁻¹, 6.07 × 10⁴ M⁻¹ respectively and photochemical yield of R + CN⁻ is 0.86. Limit of detections for CN⁻, Fe³⁺ and H₂S are 17.5 nM, 8.69 μM and 8.1 μM respectively. Receptor R is effective for real time applications, bio-compatible and has been successfully employed for confocal fluorescence imaging of RAW264.7 cell and zebrafish.