Luminescence

The spectacular luminescent behaviour of tandem terpyridyl platinum( II ) acetylide complexes.

CAS-Croucher Joint Labs

The CAS-Croucher Funding Scheme for Joint Laboratories is the outcome of an agreement between The Chinese Academy of Sciences (CAS) and the Croucher Foundati...

Luminescent platinum (II) complexes

With an increasing demand for energy coupled with dwindling resources worldwide, scientists are looking for innovative ways of sourcing alternative energy.

The key point is to have the molecule absorb the light energy. So the light will absorb the light proton and get more energy. Normally speaking, when the molecule [is] exposed to sunlight, it gets warm.

Professor CHE Chi-Ming

Electronically excited transition metal complexes are highly energetic and chemically reactive with properties and reactivity distinctly different from their ground state. Understanding the properties and their ability to manipulate the reactivity of electronically excited state species are crucial in the design of new catalysts for light-induced multi-electron transfer reactions and functional molecular materials with useful applications.

In a University of Hong Kong-Chinese Academy of Sciences Joint Laboratory collaboration supported by the Croucher Foundation Funding Scheme, scientists Dr Che Chi-ming at the University of Hong Kong and Dr Tung Chen-ho of the Chinese Academy of Sciences, have been working on developing New Molecular Materials with practical applications.

So far they have designed and prepared new classes of highly robust luminescent platinum(II) complexes containing rigid ligand scaffolds for photo-induced multi-electron transfer catalysis and/or for the construction of novel supramolecular systems containing organic ligands with extended ?-conjugations. Their main objectives are: to prepare highly robust platinum(II) complexes with long-lived and emissive metal-to-ligand charge transfer excited state in solutions at room temperature; to use photochemically active platinum(II) complexes to address fundamental issues related to energy-solving problems, for example, in the design of molecular photo-catalysts for light-induced multi-electron transfer catalysis; to explore the applications of platinum(II) photochemistry in light, such as in the photochemical organic oxidations using air as the terminal oxidant, and to develop new classes of platinum(II) compounds that can be used in molecular electronics and luminescent signalling studies.

Their short to medium term goal is to develop highly robust phosphorescent platinum(II) complexes for light-induced multi-electron transfer catalysis, that will have useful properties for applications in optoelectronics.

To date the collaboration has made contributions in developing applications for phosphorescent transition metal complexes, particularly phosphorescent platinum (II) and copper (I) complexes (HKU-Technical Institute of Physics and Chemistry). The team demonstrated that phosphorescent platinum (II) complexes offer an entry to new classes of novel functional molecular materials with unique spectroscopic, photophysical and semi-conducting properties. They also found that inexpensive copper (I) complexes can be used as building blocks for the self-assembly formation of nano-structured materials.

The collaboration has been extended to develop functional inorganic-organic hybrid materials for energy research (HKU-Institute of Chemistry) and phosphorescent platinum (II) complexes for practical high performance Organic Light-Emitting Diodes (HKU-Beijing Aglaia Technology & Development Co Ltd).

Central to the team’s photochemistry research is the design of photoactive materials for solar cell applications and photo-catalysed conversion of CO2 into fuels. Solar energy is seen as a source of clean energy and Che’s team are looking for alternative ways to absorb and control that energy. One way is the application of the principles of photosynthesis to trap solar energy.

“The key point is to have the molecule absorb the light energy- so the light will absorb the light proton and get more energy. Normally speaking, when the molecule [is] exposed to sunlight, it gets warm,” explains Che.

But, Che goes on, that'’s not always good as the molecule in this state is unstable and very hot so it is difficult to control. So far they have managed to create molecules that stores energy for one millisecond. “The ultimate aim would be creating one that stores energy for one whole second. Currently the team are working with gold and platinum, but these are expensive. “The long term programme is to walk away from the expensive metals and go to the earth abundant metals; iron, nickel, tungsten and copper.