Chemiluminescence of praseodymium (III), neodymium (III) and ytterbium (III) beta-diketonates in solution excited from 1,2-dioxetane decomposition and singlet-singlet energy transfer from ketone to rare-earth beta-diketonates

This work is concerned with the chemiluminescence (CL) of Nd3+, Yb3+ and Pr3+ beta-diketonates in solution. Chemiluminescent reaction of adamantylideneadamantane-1,2-dioxetane (AAD) decomposition generating singlet (Ad = O-S*) and triplet (Ad = O-T*) excited adamantanone was used as a source of excited species. AAD chemiluminescence due to emission from Ad = O-S* is quenched by Ln(3+) beta-diketonates: (a) by intermolecular singlet-singlet (S-S) energy transfer from Ad = O-S* to beta-diketonate ligand levels of Ln(TTA)(3). 2H(2)O and Ln(BTFA)(3). 2H(2)O; (b) by complex formation between AAD and Pr(FOD)(3) or Pr(DPM)(3). Corresponding Stern-Volmer quenching constants or stability constants of the complex were measured. Chemiluminescence spectra of Ln(3+) beta-diketonates were recorded and relative luminescence quantum yields compared. Yb3+ chelates show higher luminescence yields compared to Nd3+, due to a different efficiency of non-radiative energy degradation. Chemiexcitation of Ln(3+) ions in the systems studied occurs by: (a) intermolecular singlet-singlet energy transfer: Ad = O-S* --> L-S* --> L-T* --> Ln(3+)* (where L-S* and L-T* are the first singlet and triplet excited states of the beta-diketonate ligand); (b) intermolecular triplet-triplet energy transfer: Ad = O-T* --> L-T* --> Ln(3+)*; (c) intracomplex energy transfer from the decomposition of AAD in the complex with Ln(3+) beta-diketonate. Efficiency of chemiexcitation pathways is different for each Ln(3+) beta-diketonate and Ln(3+) ion. (C) 2000 Elsevier Science B.V. All rights reserved.