Photochromism and electrospray mass spectrum of the ternary europium system with nicotinic acid and 1,10-phenanthroline

A novel photochromic system of europium with nicotinic acid (HL) and 1,10-phenanthroline (phen) was studied. The color of the system turns from yellow to green with a broad absorption band appearing in the range 550-830 mm under the irradiation by a mercury lamp. The pH value of the system plays an important role in the photochromic behavior. It is observed that a higher pH value is favorable to photochromism. With electrospray ionization mass spectrometry (ESIMS), we probed the possible species present in the aqueous solution. It was concluded that the complex EuL3(phen)(2) . H2O exists in the solution. To better understand its ESI mass spectrum, we give the possible fragmentation of EuL3(phen)(2) . H2O.