Ternary electrofluorochromic behavior of the terpyridine Eu(III) complex with a Bis-Arylamine redox group.

The terpyridine Eu(III) complex with an alkyl-substituted phenyl-capped aniline dimer shows ternary electrofluorochromic behavior under different potentials. [Display omitted] • Terpyridine Eu(III) complexes with multiple redox states. • The resulted complex displays an unique electrofluorochromic behavior. • With ternary conversion among orange, dark-blue and pale-yellow colors. • And red, deep-blue and greenish-blue PL emissions. Three new terpyridine Eu(III) complexes, [(L 1-3)Eu(HFA) 3 ] (where L 1 = 4′-phenyl-2,2′:6′,2″-terpyridine, L 2 = 4′-{[ p -(N-butyl-N-phenyl)amino]-phenyl}-2,2′:6′,2″-terpyridine}, L 3 = 4′-{ p -[ p -(N,N′-dibutyl-N′-phenyl)-phenyldiamino]-phenyl}-2,2′:6′,2″-terpyridine, and HFA = hexafluoroacetylacetone), have been successfully synthesized and characterized by UV–vis absorption spectrum, FTIR, MALDI-TOF MS and elemental analysis. The X-ray crystallography of complex [(L 2)Eu(HFA) 3 ] shows that the europium(III) ion is nine-coordinated with N3O6 donors in normal ranges. Owing to the antenna effect, complex [(L 1)Eu(HFA) 3 ] (Ф = 0.44) possesses ca. 3 times enhancement of the metal-centered red emission intensity compared to that of precursor Eu(HFA) 3 (Ф = 0.16). The most interesting is that complex [(L 3)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. [ABSTRACT FROM AUTHOR]