In a collaboration between researchers in the Papanikolas Group and the Meyer Group, results of CW and lifetime emission studies have been used to demonstrate facile intra-strand energy transfer in the derivatized polystyrene polymer
[PS-4-CH2CH2NHC(O)-(RuII(4,4'-(CONEt2)2bpy)2)17
(OsII(bpy)2))3](PF6)40 in four rigid media: frozen 5:4 (v:v) propionitrile:butyronitrile solutions at 77 K, polymethyl-methacrylate (PMMA) and polyethylene glycol-dimethacrylate (PEG-DMA) films, and silica xerogel monoliths at room temperature.
Continued rapid energy transfer in rigid media is in contrast to electron transfer which is inhibited. This can be explained by energy transfer theory and is due to a decrease in the energy transfer barrier because of the frozen nature of the medium. The abbreviation used for the polymer defines the chemical link to the polystyrene backbone and gives the extent of loading out of 20 available sites. This was an important observation since one goal of the work with polymers was to use them as light absorbing antenna in artificial photosynthesis applications. As assemblies, the multi-site polymers were massive light absorbers but at isolated, electronically weakly coupled sites. In order to use the excited state energy for energy conversion at a remote site requires facile intra-strand energy migration and transfer on the lifetime of the polymer-bound excited states.
Water oxidation is a key reaction in natural photosynthesis and in many schemes for artificial photosynthesis. Although metal complexes capable of oxidizing water based on Ru, Mn, and Ir are known, a significant question is whether or not dimeric or higher order structures are required for water oxidation. Researchers in the Meyer and Templeton Groups report in JACS on single-site catalytic water oxidation by the monomeric complexes [Ru(tpy)(bpm)(OH2)]2+ and [Ru(tpy)(bpz)(OH2)]2+ (tpy is 2,2':6',2"-terpyridine; bpm is 2,2'-bipyrimidine; bpz is 2,2'-bipyrazine) by a well-defined mechanism involving RuV=O.
These results are important in establishing detailed mechanistic insight into water oxidation at a single ruthenium site and in paving the way toward a family of robust water oxidation catalysts. For more information about Artifical Photosynthesis and other energy solutions for the future, visit Professor Meyer's faculty page.