Recent research work from Prof. Wei Lu’s research group from the Department of Chemistry has revealed that phosphorescence of long-lived triplet excited states of organometallic complexes in aerated dimethyl sulfoxide (DMSO) solutions can be activated by controlled photo-irradiation. These results provided a novel non-contact approach towards manipulating phosphors under air.

Prof. Wei Lu’s research group

Long-lived photo-excited triplet states in fluid solutions are usually quenched by molecular oxygen through energy transfer. The sensitized singlet oxygen is a reactive species that could further damage covalent structures of the luminophores. In this context, oxygen are mandatorily removed prior to any measurements on phosphorescence emission spectra, lifetimes, and quantum yields in solutions at ambient temperatures. Repeated cycles of freeze-pump-thaw and bubbling with an inert gas, such as argon and nitrogen, are two major methods applied to deprive oxygen out from fluid solutions. Otherwise, a supramolecular matrix should be added to the solution to isolate the phosphors from oxygen quenching.

Latest results from Prof. Lu’s group reported that phosphorescence of a series of Au(I) arylethynyl complexes dissolved in aerated DMSO, which has been completely quenched by molecular oxygen, can be repeatedly switched-on at ambient temperature through controlled photo-irradiation. A trace amount of oxidation product of DMSO by the sensitized singlet oxygen has been detected, and hence a photochemical depletion of molecular oxygen in the local micro-environment is proposed for the photo-activated processes. An optical-writing and oxygen-erasing prototype based on the photo-activated phosphorescence has been demonstrated with a DMSO gel containing Au(I) arylethynyl complexes.

With Au(I) arylethynyl complexes and via photo-activation, fully developed phosphorescence can be measured in aerated DMSO solutions and technically utilized in aerated gels. The results provides a novel and non-contact approach for manipulating phosphorescence of metal-organic complexes. The pivotal factors for photo-activation include an appropriate solvent system that can sarcrifice for photo-oxidation to consume the sensitized singlet oxygen. It would be intriguing to answer the question whether their method can be generalized to any other photo-functional systems involving long-lived triplet excited states.

This work has been accomplished by Dr. Shigang Wan of Prof. Lu’s group at South University of Science and Technology of China and published on the journal of Angew. Chem. Int. Ed.. This work was supported by National Natural Science Foundation of China (21571096), National Key Basic Research Program of China (973 Program 2013CB834803), and Science and Technology Innovation Commission of Shenzhen Municipality (JCYJ20160301114634613).

Link to the published article:

Shigang Wan and Wei Lu,* Angew. Chem. Int. Ed. 2017, 56, 1784–1788.

http://onlinelibrary.wiley.com/doi/10.1002/anie.201610762/full