Tuning fluorescence properties of imidazole derivatives with thiophene and thiazole

The steric effect from aromatic species at the 2-position has been evaluated in 2,4,5-trisubstituted imidazole system. The steric interaction from the 2-position has a direct impact on the fluorescent properties. There is a correlation between the twist and fluorescence quantum yield. The larger the twist is, and the more reduction of quantum yield it will have. The use of thiazole at the 2-position almost eliminates the interaction and retains the coplanarity. As a result, the substitution at the 1-position does not compromise the quantum yield.