Structural, thermal, and fluorescence properties of Eu(DBM)(3)Phen(x) complex doped in PMMA

Tris (dibenzoylmethanido) (o-phenanthroline)-europium(III) complexes [Eu(DBM)(3)(Phen)(x)] have been synthesized, and their structural, thermal, and fluorescence properties have been investigated both as an independent complex and also after embedding it in poly(methyl methacrylate) (PMMA) polymer matrix. X-ray analysis reveals an unusual crystalline to amorphous transformation in structure of the Eu(DBM)(3)Phen(x) complexes when x exceeds 1.0 (mole %). Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis depict the interaction between the Eu(DBM)(3)Phen(x) complex and the PMMA matrix. The fluorescence intensity of Eu(3+) ion in the Eu(DBM)(3)Phen(1·5) complex is an order of magnitude larger compared to the Eu(DBM)(3)·2H(2)O complex. In addition to the transition (5)D(0) → (7)F(2,) which has a rise time of 83 μs, transitions from the (5)D(1) and (5)D(2) levels are also observed, along with several ligand field splittings in the Eu(DBM)(3)Phen(1·5) complex. Appearance of a rise time (∼0.76 ns) in the decay of the fluorescence from DBM in the presence of Phen and a simultaneous large decrease in the fluorescence intensity (both the singlet and triplet emission) of DBM along with a decrease in fluorescence decay time, in the presence of Eu(3+), indicates a cascading excitation energy transfer from Phen to DBM and finally to the (5)D(0) state of Eu(3+) ion in Eu(DBM)(3)Phen(1.5) through short-range excitation energy transfer. A systematic and significant improvement in the thermal and fluorescence properties of the complex is observed with an increase in the mole concentration of Phen. The maximum fluorescence is observed for Eu(DBM)(3)Phen(1·5), which is a new composition as compared with the usual composition reported earlier. This finding indicates the possibility for the development of brighter luminescent lanthanide photonic materials.