Coumarin–naphthalene conjugate for rapid optical detection of OCl− and Y3+ in a cascade manner: combined experimental and theoretical studies†

The coumarin–naphthalene conjugate (A3), an ESIPT-active probe, selectively recognized OCl⁻ in a ratiometric manner in DMSO–water media. The recognition was associated with sky-blue emission (under UV light) as well as yellow emission (under visible light). The OCl⁻ assisted inhibition of the ESIPT process via H-bonding resulted in an intense emission at 484 nm (λ_ex = 365 nm). It allowed for the detection of OCl⁻ as low as 18.42 nM with a strong association constant, K = 1.08 × 10⁵ M⁻¹, around physiological pH. Furthermore, the A3-OCl⁻ adduct (Ad1) ratiometrically detected Y³⁺ via bright orange emission at 556 nm (λ_ex = 440 nm) under both UV and visible light. Detection up to 98.51 nM was achieved with a binding constant, K = 1.38 × 10⁵ M⁻¹, at physiological pH. Density functional theory (DFT) and lifetime decay measurements substantiated the interactions. Real sample analysis were also achieved with the developed method.