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

Article abstract of DOI:10.1007/BF02495640

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 (k₂) of decomposition of compound 1 in the 1 · Ln(btfa)₃ complexes and their stability constants (K₁) 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 (ΔH = -5.5±0.5 kcal mol^-1, ΔS = -10.4±0.7 e.u. for 1 · Tb(btfa)₃ and ΔH = -5.8±0.5 kcal mol^-1, ΔS = -10.9+0.7 e.u. for 1 · Eu(btfa)₃) have been calculated from the temperature dependences of k₂ and K₁. The yields of excitation of the Ln(btfa)₃ chelates φ*_Eu = 0.021±0.006 and φ*_Tb = 0.12±0.04 have been determined. A higher efficiency of the occupation of the ⁵D₄-level of Tb³⁺ compared to those of the ⁵D₁- and ⁵D₀-levels of Eu³⁺ is caused by different efficiencies of the non-radiative energy dissipation in the Ln³⁺ ion after the intracomplex energy transfer from the ³n,π*-state of 2 to the resonance excited levels of lanthanides.