Facile Preparation of Highly Luminescent Materials by Electrostatic Immobilization of Anionic Metal Complex onto Anion-Exchanger as Exemplified with Tri-Terbium(III) Cluster Complex of Thiacalix[4]arene-p-tetrasulfonate

We propose a strategy to prepare luminescence materials via simple and organic solvent-free fashion by mixing an anionic luminescent complex with an anion exchanging support. As a proof-of-concept, we employed the heptaanionic Tb^III complex Tb₃TCAS₂ (TCAS = thiacalix[4]arene-p-tetrasulfonate) and QAE Sephadex A-25, a dextran support bearing anion exchanging groups. By stirring a mixture of TCAS and dextran (1.0 ¯mol Tb₃TCAS₂/50 mg dextran), 99.8% of Tb₃TCAS₂ was successfully immobilized within 2 h. The electrostatic interactions were strong enough to irreversibly bind Tb₃TCAS₂ to the dextran. The material exhibited Tb^III-centered luminescence upon excitation of the TCAS center. The luminescent lifetime and quantum yield were 1.18 ms and 45.5%, respectively. When the amount of Tb₃TCAS₂ immobilized on the dextran was reduced to 1.0 nmol/50 mg dextran, the lifetime increased to 1.32 ms, suggesting concentration quenching above 1.0 ¯mol Tb₃TCAS₂/50 mg dextran. On the other hand, the luminescence quantum yield decreased to 3.1%, suggesting that the absorption of excited light by the support was not negligible. Preparation of the materials in D₂O resulted in increases in the lifetime and quantum yields to 1.32 ms and 44%, respectively.