Luminescent Ir(iii)-Ln(iii) coordination polymers showing slow magnetization relaxation

Abstract

A series of iridium(iii)-lanthanide(iii) bimetallic coordination polymers were successfully obtained by hydrothermal reactions based on the Ir unit [Ir(ppy)2(Hdcbpy)], namely, [Ln{Ir(ppy)2(dcbpy)}2(NO3)(H2O)n]·solvent (Ir2Ln, n = 5, Ln = Gd and Dy; and n = 4, Ln = Er and Yb) and [Ln2(OH){Ir(ppy)2(dcbpy)}4(NO3)(H2O)4]·solvent (Ir4Ln2, Ln = Gd, Dy, Er, and Yb). Compounds Ir2Ln show chain structures in which the lanthanide ions are bridged by the Ir(ppy)2(dcbpy)- ligands through the carboxylate groups. Compounds Ir4Ln2 have double-chain structures, in which the dimers of Yb2(OH) are connected by the Ir(ppy)2(dcbpy)- ligands. Magnetic studies reveal that Ir2Dy and Ir4Dy2 exhibit slow magnetic relaxation behaviour in zero dc field, which is characteristic of single molecule magnets, but Ir2Er, Ir4Yb2, Ir4Er2 and Ir4Yb2 require a field to induce such characteristics. Moreover, since the iridium(iii) moiety can serve as an "antenna"to effectively sensitize the f-f transitions of the lanthanide ions, near-infrared luminescence has been observed for the YbIII and ErIII complexes. As far as we know, this is the first observation of SMM behaviour and NIR luminescence in iridium(iii)-lanthanide(iii) bimetallic coordination polymers.