Spectroscopic study on the photophysical properties of novel lanthanide complexes with long chain mono-L phthalate (L = hexadecyl, octadecyl and eicosyl)

Abstract

Ortho-phthalic anhydride was modified with long chain alcohol (1-hexadecanol, 1-octadecanol and 1-eicosanol) to their corresponding mono-L phthalate (L = hexadecyl, octadecyl and eicosyl), i.e. monohexadecyl phthalate (16-Phth), monooctadecyl phthalate (18-Phth), and monoeicosyl phthalate (20-Phth), respectively. Nine novel lanthanide (Eu 3+, Tb 3+ and Dy 3+) complexes with these three mono-L phthalate ligands were synthesized and characterized by elemental analysis and IR spectra. The photophysical properties of these complexes were studied in detail with various spectroscopes such as ultraviolet–visible absorption spectra, low temperature phosphorescence spectra and fluorescent spectra. The ultraviolet–visible absorption spectra show some band shifts with the different chain-length of phthalate monoester and homologous lanthanide complexes. From the low temperature phosphorescent emission, the triplet state energies for these three ligands were determined to be around 22,650 cm −1 (16-Phth), 23,095 cm −1 (18-Phth) and 22,400 cm −1 (20-Phth), respectively, suggesting they are suitable for the sensitization of the luminescence of Eu 3+, Tb 3+ and Dy 3+. The fluorescence excitation and emission spectra for these lanthanides complexes of the three ligands take agreement with the above predict from energy match.