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

Electronic absorption, polarized absorption and fluorescence spectra were m easured to clarify the electronic structures and the nature of elect Tonic transitions of [Nd(acac)(terpy)(NO3)(2)] and [Pr(acac)(terpy)(NO3)(2)H2O]. It is found for both complexes that the nn; transition is localized on the terpyridine moiety whereas the nn; transition can be assigned to the intram olecular CT transition from the terpyridine moiety (pi HOMO) to the acetyla cetone (pi LUMO). [Nd(acac)(terpy)(NO3)(2)] (or [Pr(acac)(terpy)(NO3)(2)N2O ]) fluoresces from the upper excited state localized on the terpyridine moi ety. This emission phenomenon is considered in detail because emissions fro m higher excited states are rarely observed. (C) 2001 Elsevier Science B.V. All rights reserved.