Higher excited state fluorescence of mixed ligand lanthanide(III) complexes with acetylacetonato, nitrate and terpyridine

Abstract Electronic absorption, polarized absorption and fluorescence spectra were measured to clarify the electronic structures and the nature of electronic transitions of [Nd(acac)(terpy)(NO 3 ) 2 ] and [Pr(acac)(terpy)(NO 3 ) 2 H 2 O]. It is found for both complexes that the ππ * 1 transition is localized on the terpyridine moiety whereas the ππ * 2 transition can be assigned to the intramolecular CT transition from the terpyridine moiety (πHOMO) to the acetylacetone (πLUMO). [Nd(acac)(terpy)(NO 3 ) 2 ] (or [Pr(acac)(terpy)(NO 3 ) 2 H 2 O]) fluoresces from the upper excited state localized on the terpyridine moiety. This emission phenomenon is considered in detail because emissions from higher excited states are rarely observed.