Ternary Electrofluorochromic Behavior of the Terpyridine Eu(III) Complex with a Bis-Arylamine Redox Group

Three new terpyridine Eu(III) complexes, [(L1-3)Eu(HFA)3] (where L1 = 4 '-phenyl-2,2 ':6 ',2 ''-terpyridine, L2 = 4 '- {[p-(N-butyl-N-phenyl)amino]-phenyl}-2,2 ':6 ',2 ''-terpyridine}, L3 = 4 '-{p-[p-(N,N '-dibutyl-N '-phenyl)-phenyl-diamino]-phenyl}-2,2 ':6 ',2 ''-terpyridine, and HFA = hexafluoroacetylacetone), have been successfully synthe-sized and characterized by UV-vis absorption spectrum, FTIR, MALDI-TOF MS and elemental analysis. The X-ray crystallography of complex [(L2)Eu(HFA)3] shows that the europium(III) ion is nine-coordinated with N3O6 donors in normal ranges. Owing to the antenna effect, complex [(L1)Eu(HFA)3] (0 = 0.44) possesses ca. 3 times enhancement of the metal-centered red emission intensity compared to that of precursor Eu(HFA)3 (0 = 0.16). The most interesting is that complex [(L3)Eu(HFA)3] displays an unique electrofluorochromic behavior with the ternary absorption (orange/dark-blue/pale-yellow) and PL emission (red/deep-blue/greenish-blue) conversions, in which the ICT, cation radicals-related and Eu(III)-centered electronic transitions are involved.