Photophysical properties of novel lanthanide (Tb3+, Dy3+, Eu3+) complexes with long chain para-carboxyphenol ester p-L-benzoate (L = dodecanoyloxy, myristoyloxy, palmitoyloxy and stearoyloxy)

In this paper, a series of 12 binary luminescent lanthanide coordination compounds with long chain p-carboxyphenol ester were assembled. Both elemental analysis and infrared spectroscopy allowed to determine the complexes formula: LnL3, where Ln = Tb, Dy, Eu; L = p-dodecanoyloxybenzoate (12-OBA), p-myristoyloxybenzoate (14-OBA), p-palmitoyloxybenzoate (16-OBA) and p-stearoyloxybenzoate (18-OBA), respectively. The photophysical properties of these complexes were studied in detail with various of spectroscopies such as ultraviolet–visible absorption spectra, low temperature phosphorescence spectra and fluorescent spectra. The ultraviolet–visible absorption spectra showed that some bands shift with the different chain length of p-carboxyphenol ester. From the low temperature phosphorescent emission, the triplet state energies for these four ligands were determined to be around 24,242 cm−1 (12-OBA), 24,612 cm−1 (14-OBA), 24,084 cm−1 (16-OBA) and 24,125 cm−1 (18-OBA), respectively, suggesting they are suitable for the sensitization of the above lanthanide ions, especially for Tb3+ and Dy3+. The fluorescence excitation and emission spectra for these lanthanide complexes of the four ligands take agreement with the above predict from energy match.