The first example of Tb₃-containing metallopolymer-type hybrid materials with efficient and high color-purity green luminescence

Abstract

In the series of homo-leptic trinuclear complexes {[Ln3(L)4Cl4(MeOH)(H2O)]·Cl} (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3 or Ln = Gd, 4) self-assembled from the allyl-modified benzimidazole-type ligand HL (4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol) and LnCl3·6H2O, a suitable energy level match endows efficient green luminescence (Φ(overall) = 72%) of Tb3-arrayed complex 3. The copolymerization between each of these complex monomers 1-4 and C=C-containing MMA (methyl methacrylate) or NBE (norbornene) shows that degradative chain transfer of the terminal four flexible allyl groups within restrains their radical polymerization with MMA while it does not hinder their effective ring-opening metathesis polymerization (ROMP) with NBE. Thus, two kinds of PMMA-supported doping hybrid materials 1@PMMA, 2@PMMA, 3@PMMA and 4@PMMA and PNBE-supported metallopolymer-type hybrid materials Poly(NBE-1), Poly(NBE-2), Poly(NBE-3) and Poly(NBE-4) are obtained, respectively. Especially for both 3@PMMA and Poly(NBE-3) with high color-purity characteristic green emission of Tb(3+) ions, improved physical properties including significantly enhanced luminescence (Φ(overall) = 76% or 83%) are observed, and covalent-bonding endows a higher-concentration self-quenching as compared to physical doping.