Near-infrared luminescent materials: From β-diketonate ytterbium complexes to β-diketonate-ytterbium-complex@PMMA thin film

In view of the potential application of NIR luminescence in biology, a series of four new 3,5-Heptanedione (β-diketonate) ytterbium complexes, e.g. [Yb(L)3(H2O)2] (1), [Yb(L)3(2,2′-bpy)] (2), [Yb(L)3(dpq)] (3) and [Yb(L)3(dppz)] (4) have been designed and isolated. Crystal structures analysis show that all complexes 1-4 exhibit the similar mononuclear structure, in which the central Yb3+ ion is eight-coordinated forming the square-anti-prismatic geometry. NIR luminescence of all complexes 1-4 shows strong characteristic emission of Yb3+ ions. To improve the mechanical and thermal stability, complex 1 was further doped into poly-(methyl methacrylate) (PMMA) for preparing a thin film (1@PMMA). Their thermal stability and NIR luminescence were essentially enhanced in contrast to that for complex 1. This NIR luminescent thin film may be of potential applications in biological dictation and luminescent probe.