Hydrogen-Bonding-Induced Fluorescence: Water-Soluble and Polarity-Independent Solvatochromic Fluorophores

Fluorophores with emission wavelengths that shift depending on their hydrogen-bonding microenvironment in water would be fascinating tools for the study of biological events. Herein we describe the design and synthesis of a series of water-soluble solvatochromic fluorophores, 2,5-bis(oligoethylene glycol)oxybenzaldehydes (8-11) and 2,5-bis(oligoethylene glycol)oxy-1,4-dibenzaldehydes (14-17), based on a push-pull strategy. Unlike typical examples in this class of fluorophores, the fluorescence properties of these compounds are independent of solvent polarity and become fluorescent upon intermolecular hydrogen-bonding, exhibiting high quantum yields (up to ϕ = 0.55) and large Stokes shifts (up to 134 nm). Furthermore, their emission wavelengths change depending on their hydrogen-bonding environment. The described fluorophores provide a starting point for unprecedented applications in the fields of chemical biology and medicinal chemistry.