Protonation of the imino nitrogen deactivates the excited state of imidazolin-5-one in the solid state

Abstract

The imino nitrogen of p-methoxybenzylideneimidazolinone (pMBDI) was protonated using aqueous $$\hbox {HClO}_{4}$$ and HCl acid and crystallized in monoclinic crystal system with $$\textit{P2}_{\textit{1}}/n$$ space group. Interestingly, the protonated compounds are fluorescent in polar solvents but non-fluorescent in non-polar solvent as well as in the solid state. These results point to the existence of a non-radiative pathway involving the imidazole nitrogen in the quenching of excited states in these compounds. SYNOPSIS The imino nitrogen of p-methoxybenzylideneimidazolinone (pMBDI) was protonated and crystallized in monoclinic crystal system with $$\textit{P2}_{\textit{1}}/n$$ space group. Interestingly, the protonation at imino nitrogen of imidazolinone ring results in the loss of the fluorescence property of gfp chromophore analogue (p-methoxybenzylideneimidazolinone).