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

Abstract

Abstract 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 TbIII 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 µmol 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 TbIII-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 µmol 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.