Energy transfer in complexes between a crown ether and various lanthanide salts

• Published in: Journal of photochemistry Vol. 12; no. 1; pp. 31 - 39
• Main Authors: de B. Costa, Sílvia M., Manuela Queimado, M., da Silva, J.J.R.Fraústo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1980
• ISSN: 0047-2670
• DOI: 10.1016/0047-2670(80)85078-7

The spectroscopic properties of complexes between benzo-15-crown-5 and europium and terbium nitrates, thiocyanates and perchlorates were investigated. The ligand fluorescence quantum yield in all the complexes is less than that of the uncomplexed crown ether, and in the complexes with terbium salts this quenching is accompanied by a sensitized emission from the metal ion. An intramolecular energy transfer from the excited singlet of the ligand to the metal ion is suggested to explain the emission from the metal ion. It is proposed that the charge transfer states associated with the lanthanide salts compete with the metal ion for the intramolecular transfer of excitation, and that this is important for the nitrate and thiocyanate complexes.