Series of Highly Luminescent Macrocyclic Sm(III) Complexes: Functional Group Modifications Together with Luminescence Performances in Solid-State, Solution, and Doped Poly(methylmethacrylate) Film

Here,
we report our trials to regulate the luminescence performance
of the macrocyclic samarium­(III) complex and prepare four excellent
luminescent Sm­(III) complex-doped poly­(methylmethacrylate) (PMMA)
composites. Four 23-membered [1 + 1] Schiff-base macrocyclic mononuclear
Sm­(III) complexes, Sm-2a–Sm-2d, originating from dialdehydes
with different pendant arms and 1,2-bis­(2-aminoethoxy)­ethane, have
been constructed by the template method. Crystal structures reveal
that every Sm­(III) ion with the coordination geometry of a distorted
bicapped square antiprism is capsulated by the macrocyclic cavity
environment forming the “lasso-type” protection. Relative
photophysical properties of macrocyclic Sm­(III) complexes are carefully
investigated in solid-state, methanol solution, and doped PMMA film,
and all these show characteristic emissions of the Sm­(III) ion associated
with satisfactory lifetimes and quantum yields in all media, which
could be comparable to reported outstanding examples. Especially,
the luminescence performance for this type of Sm­(III) complex could
be regulated in the solid state by the use of different functional
groups in the pendant arm while it is not achieved in solution and
the doped PMMA composite. High emitting and air-stable plastic materials
could be obtained when these Sm­(III) complexes are doped in PMMA with
0.1 wt % mixing ratio, and the corresponding maximum lifetime and
quantum yield are 61.2 μs and 0.63% in the case of complex Sm-2a, respectively. We believe that
these highly luminescent “lasso-type” Sm­(III) complexes
and doped PMMA composites are valuable references in the design of
luminescent lanthanide­(III) hybrid materials.