Chemiluminescence and catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) in the presence of EuIII and TbIII tris(benzoyltrifluoroacetonate) complexes

Catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) (1) in the presence of Eu-III and Tb-III tris(benzoyltrifluoroacetonate) complexes (Ln(btfa)(3)) accompanied by the formation of adamantanone (2) and chemiluminescence (CL) was studied. The rate constants (k(2)) of decomposition of compound 1 in the 1.Ln(btfa)(3) complexes and their stability constants (K-1) have been determined. The Arrhenius parameters of decomposition of 1 (E-a = 22.4 +/- 0.7 kcal mol(-1), logA = 10.2 +/- 0.8 for 1.Tb(btfa)(3) and E-a = 23.4 +/- 0.6 kcal mol(-1), logA = 10.6 +/- 0.8 for 1.Eu(btfa)(3)) and thermodynamic parameters of complex formation (Delta H = -5.5 +/- 0.5 kcal mol(-1), Delta S = -10.4 +/- 0.7 e.u. for 1.Tb(btfa)(3) and Delta H = -5.8 +/- 0.5 kcal mol(-1), Delta S = -10.9 +/- 0.7 e.u. for 1.Eu(btfa)(3)) have been calculated from the temperature dependences of k(2) and K-1. The yields of excitation of the Ln(btfa)(3) chelates phi*(Eu) = 0.021 +/- 0.006 and phi*(Tb) = 0.12 +/- 0.04 have been determined. A higher efficiency of the occupation of the D-5(4)-level of Tb3+ compared to those of the D-5(1)- and D-5(0)-levels of Eu3+ is caused by different efficiencies of the non-radiative energy dissipation in the Ln(3+) ion after the intracomplex energy transfer from the (3)n,pi*-state of 2 to the resonance excited levels of lanthanides.