Fluorescence Red-Shifting of GFP-like Chromophores by Enhancing Electronic Donor-Acceptor Strength

Meta-Amino substituted green fluorescence protein chromophores (GFPc) such as m-DMABDI display strong fluorescence in non-polar aprotic solvent (Φf = 0.46 in n-Hex)as a result of “meta-amino substituent effect” but undergo fluorescence quehching in protic solvents due to solvent–solute H-bond interactions. This type of chromophore has been applied on bioimaging, which showed green fluorescence in human mammary epithelial cells.However, fluorescent dyes with green emission maybe interfered by autofluorescence of biological sample. In order to avoid this probleme, developing chromophores of red-shifted emission is necessary. In this thesis, we have three strategies to red-shift the emission of m-DMABDI :(1) introducingo-hydroxyl group into m-DMABDI, to induce tautomer emission throughexcited-state intramolecularproton transfer(ESIPT)(o-OH); (2) introducing strong electron-donating(methoxy)groupinto the donor of m-DMABDIto enhance the push-pull strength of chromophore (o-OMe and p-OMe); (3) introducingelectron-accepting(dicyanomethylene)groupinto the acceptor moiety of m-DMABDIto not only enhance the donor-acceptorstrength but also to extend the conjugation length (m-DMABDI-2CN). Our results show that the emission maximum of o-OMe is red-shifted as compared with that of m-DMABDIby 50-60 nm.