New porphyrins tailored as biodiesel fluorescent markers

This work reports the synthesis, characterization, and evaluation of new porphyrins tailored to become biodiesel fluorescent markers. The compounds were obtained by the synthetic modification of the commercially available porphyrin 5,10,15,20-meso-tetrakis(pentafluorophenyl)porphyrin (TPPF20) using ethanol and hexadecan-1-ol (cetylic alcohol) as nucleophilic reagents.The stability of the marked biodiesel fuel solutions was investigated every 15 days for a total period of 3 months, and under different storage temperature and light exposure condition, simulating the conventional stock conditions. The influence of the different substituents of the porphyrins on the fluorescence properties of the biodiesel fuel markers was also assessed.The resulting porphyrins were highly soluble in biodiesel fuel and displayed strong fluorescence characterized by two strong emission bands. The fluorescent markers did not affect the biodiesel physical properties and were stable in storage conditions for at least 3 months at a concentration of 4 ppm.The best storage condition was found to be absence of light and 6 °C; the limit of detection by photoluminescence technique had magnitude of 10−13 mol L−1.The synthesized porphyrins were characterized by nuclear magnetic resonance (1H-NMR and 19F-NMR), mass spectrometry (HRMS), ultraviolet visible absorption spectroscopy, and photoluminescence spectroscopy.

► TPPF20 porphyrin derivatives used as biodiesel fluorescent markers.
► Improvement of TPPF20para nucleophilic substitution with ethanol or hexadecane-1-ol.
► Four storage conditions tested for the marked biodiesel.
► Best storage condition is 6 °C and absence of light.
► TPPF20 porphyrin derivatives are promising biodiesel markers.