Furandicarboxylate derivatives as excellent fluorescence standards: Spectroscopical and electrochemical study

Six furandicarboxylate derivatives were proposed as fluorescence standards for instrumental calibration procedures and luminescence measurements. Their spectroscopical characteristics such as fluorescence quantum yields (ΦFL) and chemiluminescence quantum yields (ΦCL) were determined and compared to those of the universally accepted fluorescence standards. Their outstanding characteristics such as high fluorescence quantum yields, moderate chemiluminescence quantum yields, excellent stability, resistance to UV-induced photodegradation and simple and unstructured emission spectra make them preferable alternatives to the well-known and widely used fluorescence standards such as luminol and anthracene. The effects of the electron donating ability, resonance ability, rigidness and steric hindrances of the fluorophore substituents on the emission characteristics of the studied fluorophores were investigated. It was found that the presence of the cyclohexyl and ethenyl substituents in the molecular structures of the studied fluorophores can significantly enhance the rigidity of the fluorophore structures and hence, enhance the fluorescence quantum yields of the fluorophores. On the other hand steric hindrances of the tert-butyl substituents can reduce the chemiluminescence quantum yields of the studied fluorophores. In addition, presence of biphenyl-ethenyl substituents on the furan ring can improve the kinetic of the electron transfer and result in the reversible oxidation of the fluorophores.