Intramolecular energy transfer models and energy band characteristic of rare-earth complexes with o-phthalic acid

doi:10.1016/j.jlumin.2006.01.208

Journal of Luminescence

Volumes 122–123, January–April 2007, Pages 467-470

https://doi.org/10.1016/j.jlumin.2006.01.208 Get rights and content

Abstract

In this study, ternary and binary europium complexes of o-phthalic acid are synthesized. Their compositions are characterized by element analysis and IR spectra and ascertained to be Eu₂(o-phthalic)₃4(H₂O) and Eu₂(o-phthalic)₃(phen)₂2(H₂O), respectively. The UV–Vis spectrum and photoluminescence spectra are also analyzed. Meanwhile, the energy transfer models have been set up and structure of energy band and optical gap of the ternary complex powder were obtained by the UV–Vis spectrum.

Introduction

Rare-earth complexes of aromatic carboxylic acids with excellent luminescent properties have been studied in recent years [1], [2], [3], which still has lots of deficiency at the brightness and lifetime comparing with β-diketone types. The luminescence properties of many materials can be improved by adding the second ligand.

In order to study the energy transfer process and the effects of ligands on luminescent properties of rare-earth complexes, ternary and binary complexes have been synthesized. The o-phthatic acid was chosen as the first ligand. The 1,10-phenantroline is suitable for energy transfer as the second ligand, which has two nitrogen atoms and more stable structure. Their spectral characteristics and intramolecular energy transfer process was studied.

Section snippets

The preparation of complexes

The binary europium complex was obtained by reaction of aqueous solution of europium ion and ethanol solution of potassium hydrogen phthalate. The mixture was stirred at 60 °C for 2 h. The product was collected, washed and dried. Finally, the white powder of binary complex was obtained. The synthesis route of the ternary complex is as follows: aqueous solution of europium ion was added into the mixed ethanol solution of potassium hydrogen phthalate and 1,10-phenantroline, stirring at 60 °C, and

UV–Vis absorption spectra

The UV–Vis absorption spectra of the binary and ternary complexes and ligands were all measured in the ethanol solvent. The peak wavelengths of UV–Vis absorption spectra are shown in Table 2. The results show that there is little difference between two complexes at UV–Vis spectra after adding the second ligand of 1,10-phenantroline. The absorption peak allocated at 262 nm of the binary and ternary complexes is ascribed to π→π* transition of benzene of o-phthalic acid.

Optical gap of Eu₂(o

Acknowledgments

This work is supported financially by National Basic Research Program of China (2004CB217808), National Natural Science Foundation of China (20271037, 20471041), Major Project of National Natural Science Foundation of China (90306014), Natural Science Foundation of Shanxi (20041066) and Scientific Research Foundation for the Returned Chinese Overseas Scholars of Shanxi (200523).

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