Visible-Light Excitable Highly Luminescent Molecular Plastic Materials Derived from Eu3+-Biphenyl Based β-Diketonate Ternary Complex and Poly(methylmethacrylate)

Abstract

In the present work, a β-diketonate ligand, namely, 1-(4′-methoxy-[1,1′-biphenyl]-4-yl)-4,4,4-trifluoro-3-hydroxybut-2-en-1-one (HMeOBPhTFB), which contains a conjugated methoxy-substituted biphenyl unit, as well as a polyfluorinated alkyl group, was synthesized and utilized for the construction of two new Eu3+ complexes [Eu(MeOBPhTFB)3(H2O)(C2H5OH)] 1 and [Eu(MeOBPhTFB)3(TPY)] 2 where TPY denotes 2,2′:6′,2′′- terpyridine. The synthesized compounds are well characterized by various spectroscopic techniques, and their solid-state photophysical properties were investigated. For comparison, Eu3+ complexes {[Eu(BPhTFB)3(H2O)(C2H5OH)] 3 and [Eu(BPhTFB)3(TPY)] 4} were also designed involving an unsubstituted biphenyl based β-diketonate ligand, 1-[1,1′-biphenyl]-4-yl)-4,4,4-trifluoro-3-hydroxybut-2-en-1-one (HBPhTFB). The results disclosed that the methoxy-substituted biphenyl based polyfluorinated Eu3+-β-diketonate complexes significantly red-shifted the excitation maximum to the visible region (λex = 400 nm) with promising solid-state quantum yield (Φoverall = 62% for 2) as compared to simple Eu3+-biphenyl β-diketonate ternary complex (λex = 382 nm for 3 and 4). In the current work, attempts also have been made to isolate luminescent molecular plastic materials by incorporating the unique photophysical properties of the developed visible-light excitable Eu3+-β-diketonate complex (2) with the mechanical, thermal and chemical stability, and flexibility and a film-forming tendency of poly(methylmethacrylate) [PMMA]. The developed molecular plastic materials were characterized and evaluated their photoluminescence properties. Most importantly, the newly constructed polymer films exhibit remarkable quantum yields (75–79%) under blue-light excitation as compared to many of the existing Eu3+ based polymeric materials.