Sandglass-Typed Single Chameleon Luminophore for Water Mapping Measurements: Intramolecular Energy Migrations in the Hydrophilic Tb(III)/Sm(III) Cluster.

Novel hydrophilic and color-changeable single chameleon luminophores composed of Tb(III)/Sm(III) nona-nuclear clusters [Tb x Sm 9- x (Sal-PEG- n ) 16 (μ-OH) 10 ] + (NO 3 ) - ( x = 1, 2, 3, and 9; Sal-PEG- n : salicylate polyethylene glycolmethylester, n = 2 and 4) are reported for water mapping measurements. Their characteristic sandglass structures and aggregates were analyzed using X-ray single crystal analysis and dynamic light scattering (DLS) measurements. The green- and yellow-luminescence of [Tb 3 Sm 6 (Sal-PEG-4) 16 (μ-OH)] + (NO 3 ) - in water were observed at 20 and 50 °C, respectively. The ratio-metric luminescence analysis using green Tb(III) and orange Sm(III) emission bands is a promising candidate for exact temperature distribution measurements in fluid dynamics. The effective temperature-sensing property based on the competitive intramolecular energy transfer processes between Tb(III)-to-ligand and Tb(III)-to-Sm(III) in a non-a-nuclear cluster is explained using temperature-dependent kinetic analyses in the excited state.