Design of ratiometric monoaromatic fluorescence probe via modulating intramolecular hydrogen bonding: A case study of alkaline phosphatase sensing.

Monoaromatic molecules are a category of molecules containing a single aromatic ring which generally emit light in the ultraviolet (UV) region. Despite their facile preparation, the UV emission greatly limits their application as organic probes. In this study, we developed a general method to red shift the emission of monoaromatic molecules. Significant fluorescence red-shift (∼100 nm per intramolecular hydrogen bonding) can be achieved by introducing intramolecular hydrogen bonding units to benzene, a typical monoaromatic molecule. Upon increasing the number of hydrogen bonding units on the benzene ring, UV, blue, and green emissions are screened, which are switchable by simply breaking/restoration the intramolecular hydrogen bonding. As a demonstration, with the breaking of one intramolecular H-bonding, the green emission (λ em max = 533 nm) of 2,5-dihydroxyterephthalic acid (DHTA) changed to cyan (λ em max = 463 nm) upon the formation of its phosphorylated form (denoted as PDHTA), which, in the presence of alkaline phosphatase (ALP), hydrolyzed and recovered the green emission. By taking advantage of the switchable emission colors, ratiometric in vitro and endogenous ALP sensing was achieved. This general approach offers a great promise to develop organic probes with tunable emissions for fluorescence analysis and imaging by different intramolecular hydrogen bonding. Image 1 • Intramolecular hydrogen bonding-induced large red emission-shift of monoaromatics was presented. • Ratiometric fluorescence variation of monoaromatics by altering intramolecular hydrogen bonding was realized. • A sensitive and selective ratiometric fluorescence probe for evaluating alkaline phosphatase activity was proposed. • The visualization of endogenous alkaline phosphatase was achieved. [ABSTRACT FROM AUTHOR]