Synthesis and spectroscopic characterization of novel GFP chromophore analogues based on aminoimidazolone derivatives

Abstract In order to improve the fluorescence properties of the green fluorescent protein chromophore, p ‑ HOBDI ((5‑(4‑hydroxybenzylidene)‑2,3‑dimethyl‑3,5‑dihydro‑4H‑imidazol‑4‑one), sixteen dihydroimidazolone derivates were synthesized from thiohydantoin and arylaldehydes. The synthesis developed is an efficient, novel, one-pot procedure. The study provides a detailed description of the spectroscopic characteristics of the newly synthesized compounds, using p ‑ HOBDI as a reference. The new compounds all exhibited significantly stronger fluorescence than p ‑ HOBDI , up to 28 times higher quantum yields. An experimental and theoretical investigation of the relationship of the fluorescence properties with the molecular structure was also carried out. A good correlation was found between the emission wavenumber and the Hammett constant of the functional group, which suggests the intermolecular charge transfer (ICT) mechanism between the aromatic groups.