ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7

Published monthly

Substituent and solvent effects on HOCl sensing by novel ESIPT-based dual emission fluorescent probes: a TD-DFT study

Fatemeh Hassani Ghezelgechi and Hossein Roohi

Department of Applied Chemistry, Faculty of Chemistry, University of Guilan, Rasht, Iran

Abstract:

Hypochlorous acid (HOCl) plays a crucial role in human health because it is involved in many biological processes. Therefore, accurately detecting and monitoring HOCl is vital for ensuring safety and understanding its impact in both environmental and biological systems. This study investigated the potential and effectiveness of four novel ESIPT-based fluorescent probes, RBT-S, RBT-SO, RBT-Se, and RBT-SeO, utilized in detecting HOCl in both gas and aqueous phases at the PBE0/6-311++G(d,p) level of theory. All probes exhibited not only enol emission but also strong fluorescence emission from the S₁-K to S₀-K transition. The oxidation causes a significant shift in the ESIPT emission wavelengths: RBT-SO exhibits a red shift to 705 nm (f = 0.08), while RBT-SeO shows a blue shift to 482.1 nm (f = 0.8). The observed red shifts in ESIPT emission of RBT-S, RBT-SO, RBT-Se, and RBT-SeO probes are 159.3 nm, 210 nm, 154.9 nm, and 122.7 nm, respectively. This indicates that upon oxidation, the Stokes shift increases for RBT-S and decreases for RBT-Se. Such distinct shifts upon oxidation are crucial for designing ratiometric fluorescent sensors capable of detecting oxidative species like HOCl. These changes highlight the tunability of the studied ESIPT-based systems for oxidation-responsive fluorescence sensing and biological imaging, where precise control over emission properties is critical. Based on hole-electron analysis data (positive t index, high D_CT, μ_CT), large red-shifts to NIR for bioimaging, and long fluorescence lifetimes for high efficiency, RBT-S is predicted to be more suitable for HOCl detection than RBT-Se.

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04559-7

Chemical Papers 80 (3) 2899–2926 (2026)

Thursday, April 30, 2026