Oxygen quenching of the excited MLCT state of ruthenium (II) bipyridyl heteroleptic complexes and singlet oxygen thereby produced

Document Type : Original Article

Authors

1 Department of Chemistry, Faculty of Science, Ain Shams University, 11566 Abbassia, Cairo, Egypt.

2 Department of Chemistry, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, and Institute of Basic and Applied Sciences, Egypt-Japan University of Science and Technology, Egypt.

Abstract

Photophysical properties of some heteroleptic bipyridyl ruthenium (II) complexes are investigated.  The lifetimes of the excited triplet metal to ligand charge transfer states, 3MLCT, of the complex ions are about 0.60±0.05 ms with two exceptions where the lifetimes drop to 2.4 ns for [Ru(bpy)2(dmp)]2+, dmp=2,9-dimethyl-1,10-phenanthroline and 1.50 ms for [Ru(bpy)2(dpp)]2+, dpp=4,7-diphenyl-1,10-phenanthroline. The rate constants, kq, for quenching in acetonitrile of the 3MLCT states of these ruthenium complex ions by molecular oxygen, O2(3Sg-), and the variations in the efficiency, fDT, with which excited singlet oxygen, O2*(1Dg), is thereby produced are reported. The quenching rate constants are in the range 1.5- 2.2 x 109 dm3 mol-1 s-1 and efficiencies of singlet oxygen production are in the range 0.55- 0.85. The inverse correlation kq and fDT is not observed for the current set of complexes.

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