Near-infrared (NIR) luminescent metallopolymers based on Ln4(Salen)4 nanoclusters (Ln = Nd or Yb)

Abstract

A series of novel Wolf Type II Ln³⁺-containing metallopolymers PNBE-co-Ln₄(Salen)₄ (Ln = La, Nd, Yb, Er or Gd) are obtained from the controlled ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and the homoleptic tetranuclear [Ln₄(L)₂(HL)₂Cl₂(μ₃-OH)₂]·2Cl (Ln₄(Salen)₄, Ln = La, 1; Nd, 2; Ln = Yb, 3; Ln = Er, 4; Ln = Gd, 5) self-assembled from the diallyl-modified flexible hexadentate Salen-type Schiff-base ligand H₂L (N,N′-bis(5-allyl-3-methoxysalicylidene)cyclohexane-1,2-diamine) with LnCl₃·6H₂O. The results of their photophysical properties show that the strong and characteristic near-infrared (NIR) luminescent Ln³⁺-centered emissions for PNBE-co-Ln₄(Salen)₄ (Ln = Nd, 2; Yb, 3) are retained with relatively higher intrinsic quantum yields than the corresponding monomers in solution, and the concentration self-quenching of Ln³⁺-based materials could be effectively prevented in both solution and solid states.