By using the in situ synthesis technique, the complex of europium with thenoyltrifluoroacetone. (TTA) and triphenylphosphine oxide (TPPO) was confirmed to synthesize in the transparent monolithic ORMOSIL during heat treatment by IR and photoluminescence spectra. The ORMOSIL doped with the EuTFA-TPPO in situ complex appears to have rather high luminescence intensity and relative intensity ratio of D-5(0)--> F-7(2)/D-5(0)--> F-7(1), i.e., better monochromaticity. The emission intensity of the Eu3+ ions in the ORMOSIL heated at 100 degreesC for 24 h increases by a factor of about 1400 compared to that in the no heat treatment sample. Laser excited high-resolution spectra indicate that the molecular structure of the Eu-TTA-TPPO in situ complex is similar to that of the Eu(TTA)(3)(TPPO)(2) complex. The effective site symmetry of the Eu3+ ion in the Eu-TTA-TPPO in situ complex as well as in the Eu(TTA)(3)(TPPO)(2) complex may be C-1 or C-2 or C-S. It is reasonable to suggest that the Bu-TTA-TPPO in situ complex may be Eu(TTA)(3)(TPPO)(2).