Luminescence enhancement of terbium(III) perchlorate by 2,2′-dipyridyl on bis (benzylsulfinyl)methane complex and luminescence mechanism

A novel ternary complex, Tb2L4 center dot L'center dot(ClO4)(6)center dot 8H(2)O, has been synthesized using bis(benzylsulfinyl) methane as the first ligand L and 2,2'-dipyridyl as the second ligand L'. The ternary complex was characterized by element analysis, molar conductivity, coordination titration analysis, infrared, thermogravimetric-differential scanning calorimetric and ultraviolet spectra. The results indicated that the composition of the complex was Tb2L4 center dot L'center dot(ClO4)(6)center dot 8H(2)O (L = C6H5CH2SOCH2SOCH2C6H5; L' = Dipy). Fourier transform infrared results revealed that the perchlorate group was bonded with the Tb(III) ion by the oxygen atom, and the coordination was bidentate. The fluorescent spectra illustrated that the complex displayed characteristic fluorescence in the solid state. After the introduction of the second ligand, 2,2-dipyridyl, the relative emission intensity and fluorescence lifetime of the ternary complex Tb2L4 center dot L'center dot(ClO4)(6)center dot 8H(2)O were enhanced compared to the binary complex TbL2.5(ClO4)(3)center dot 3H(2)O. This indicated that the presence of both organic ligand bis(benzylsulfinyl) methane and the second ligand 2,2-dipyridyl could sensitize the fluorescence intensity of Tb(III) ion, and introduction of the 2,2-dipyridyl group resulted in an enhancement of the fluorescence of the Tb(III) ternary rare earth complex. The strongest characteristic fluorescence emission intensity of the ternary complex was 9.36 times that of the binary complex. The phosphorescence spectra and fluorescence lifetime of the complex were also measured. Copyright (C) 2014 John Wiley & Sons, Ltd.