Near-Infrared Luminescent PMMA-Supported Metallopolymers Based on Zn–Nd Schiff-Base Complexes

On the
basis of self-assembly from the divinylphenyl-modified Salen-type
Schiff-base ligands H2L1 (N,N′-bis­(5-(3′-vinylphenyl)-3-methoxy-salicylidene)­ethylene-1,2-diamine)
or H2L2 (N,N′-bis­(5-(3′-vinylphenyl)-3-methoxy-salicylidene)­phenylene-1,2-diamine)
with Zn­(OAc)2·2H2O and Ln­(NO3)3·6H2O in the presence of pyridine (Py),
two series of heterobinuclear Zn–Ln complexes [Zn­(Ln)­(Py)­Ln­(NO3)3] (n = 1, Ln = La, 1; Ln = Nd, 2; or Ln = Gd, 3 and n = 2, Ln = La, 4; Ln
= Nd, 5; or Ln = Gd, 6) are obtained, respectively.
Further, through the physical doping and the controlled copolymerization
with methyl methacrylate (MMA), two kinds of PMMA-supported hybrid
materials, doped PMMA/[Zn­(Ln)­(Py)­Ln­(NO3)3] and Wolf Type
II Zn2+–Ln3+-containing metallopolymers Poly­(MMA-co-[Zn­(Ln)­(Py)­Ln­(NO3)3]), are obtained, respectively.
The result of their solid photophysical properties shows the strong and characteristic near-infrared
(NIR) luminescent Nd3+-centered emissions for both PMMA/[Zn­(Ln)­(Py)­Nd­(NO3)3] and Poly­(MMA-co-[Zn­(Ln)­(Py)­Nd­(NO3)3]), where ethylene-linked hybrid materials endow relatively
higher intrinsic quantum yields due to the sensitization from both 1LC and 3LC of the chromorphore than those from
only 1LC in phenylene-linked hybrid materials, and the
concentration self-quenching of Nd3+-based NIR luminescence
could be effectively prevented for the copolymerized hybrid materials
in comparison with the doped hybrid materials.