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

Abstract

The terpyridine Eu(III) complex with an alkyl-substituted phenyl-capped aniline dimer shows ternary electrofluorochromic behavior under different potentials. • 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.