In silico design of two‐photon fluorescent probes for detecting nitric oxide

Abstract

With the extensive use of two‐photon fluorescence microscopy in the biology field, the need for developing fluorescent probes with preferred two‐photon absorption (TPA) properties has attracted great interest. Nitric oxide (NO) is a ubiquitous signaling molecule in a variety of physiological and pathological process in living organisms. A two‐photon (TP) probe, that is, 2‐acetyl‐6‐dialkylaminonaphthalene as the reporter and an o‐diaminobenzene as the reaction site for NO, linked by prolinamide (ANO1) has been synthesized. Based on the experimental study, five other TP probes have been theoretically designed by substituting the naphthalene fluorophore with luciferin, pyrene (substitution at 1,6‐position and 2,7‐position), fluorene, and boron‐dipyrromethene units. DFT/TDDFT studies have been conducted one‐photon absorption and emission properties as well as TPA. Our results indicated that both absorption and emission spectra of designed probes show red shifts compared with ANO1. Moreover, the fluorescence intensities are enhanced after reaction with NO. Furthermore, molecular orbitals are analyzed to interpret the photoinduced electron transfer mechanism. Notably, introducing the fluorene moiety can induce the enhancement of μ0n and Δμ0n and thus modulate TPA. Accordingly, ANO4 is thought to be a promising candidate for novel TPA NO probe.