The objective: Although singlet oxygen (the first excited state of ground state oxygen) research has been of great interest to many research groups since the 1960s, little information is available on the photophysical properties of transition metal complexes that sensitize the production of singlet oxygen. Therefore, the goals of this project is to measure the singlet oxygen production of a series of iridium(III) and platinum(II) complexes and to characterize these compounds' properties.
Through time-resolved laser spectroscopy the singlet oxygen quantum yields and quenching rates (rate of singlet oxygen deactivation) of cyclometalated octahedral iridium(III) and square planar platinum(II) complexes were determined.
Many of the complexes tested have high quantum yields (0.4-1.0) and slow quenching rates when compared to most sensitizers.
The relatively high quantum yields of singlet oxygen are attributed to the geometry of the complexes and the electronic conjugation between then ligands and metal center. Singlet oxygen quantum yields also appear to correlate more with the choice of the cyclometalating ligand than the ancillary ligand of the compound.
Singlet oxygen is believed to be the only product formed due to several factors including metal to ligand charge transfer and the unlikely occurrence of electron transfer in our system.
The results augment current understanding of transition metal photosensitizers and show promise for application of similar photosensitizers to photodynamic therapy.
Particularly interesting is that these transition metal complexes can be easily altered to fit its biological application by changing the cyclometalating or ancillary ligands.
This project characterizes a group of metal compounds that generate singlet oxygen.
Science Fair Project done By Henry Fong