Luminescence and Magnetic Properties of Tb(III) Complexes with TETA and Synergistic Effect by 1,10-Phenanthroline

Two Tb(III) complexes, [Tb(TETA)]− and [Tb(TETA)(phen)]− (TETA = 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate and phen=1,10-phenanthroline), were synthesized and their luminescence (⁵D₄ → ⁷F_=0-6 transitions) and magnetic properties were examined. The photoluminescence (PL) quantum yield of [Tb(TETA)(phen)]− (Q = 0.47) was significantly higher than that of [Tb(TETA)]− (Q = 0.006). The dramatic increase (78 x) in green luminescence was attributed to intramolecular energy transfer from phen to Tb(III). The energy transfer rate according to Dexter theory was found to be approximately 1011s−1. The temperature dependence of the molar susceptibilities confirmed that the two complexes behave as paramagnets obeying the Curie–Weiss law. In addition, the field-dependent magnetization of the two complexes measured in the −70 to + 70 kOe range at T=1.8K fitted well with the Brillouin function with the following values: g _eff=1.5, μ B =9.27×10−21 emu, and J=6. These results provide new insights into the development of lanthanide metal complexes with tetraaza