Synthesis and photophysical properties of bis(phenylpyridine) iridium(III) dicyanide complexes

Abstract

Our research group is focusing on luminescence of coordination compounds which based on cyanide bridging interactions. Recently, four cyanometallate complexes based on Ir(III) complex [Ir(ppy)2(CN)2]-, which is one of an extensive family of Ir(III) complexes based on cyclometallating phenylpyridine ligands that have achieved prominence for their desirable photophysical properties, were successfully synthesised. The present study showed that, the introduction of fluorine atoms to the phenyl rings could enhance the triplet excited state energy and thus caused a blue-shift phosphorescence peak (λem = 453 nm) as shown by (PPN)[Ir(2,4-F2ppy)2(CN)2] (1) compared to that of complex without fluorine atom (PPN)[Ir(ppy)2(CN)2] (4) (λem=474 nm). However, (PPN)[Ir(3,5-F2ppy)2(CN)2] (2) shows a negligible hypsochromic shift (λem = 473 nm) in the emission. Conversely, (PPN)[Ir(4-CF3ppy)2(CN)2] (3) shows a red-shift (λem = 479 nm) compared to complex (4). These complexes, like [Ru(bipy)(CN)4]2−, have a strong emissive and high energy excited state and thus, are potentially good energy donors; and are anionic with cyanide groups, and so can form cyanide-bridged complexes with other metal and lanthanide cations.