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A Series of Supramolecular Complexes for Solar Energy Conversion via Water
Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of
Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors
#MMPMID28817031
White TA
; Knoll JD
; Arachchige SM
; Brewer KJ
Materials (Basel)
2011[Dec]; 5
(1
): 27-46
PMID28817031
show ga
Mixed-metal supramolecular complexes have been designed that photochemically
absorb solar light, undergo photoinitiated electron collection and reduce water
to produce hydrogen fuel using low energy visible light. This manuscript
describes these systems with an analysis of the photophysics of a series of six
supramolecular complexes, [{(TL)?Ru(dpp)}?RhX?](PF?)? with TL = bpy, phen or
Ph?phen with X = Cl or Br. The process of light conversion to a fuel requires a
system to perform a number of complicated steps including the absorption of
light, the generation of charge separation on a molecular level, the reduction by
one and then two electrons and the interaction with the water substrate to
produce hydrogen. The manuscript explores the rate of intramolecular electron
transfer, rate of quenching of the supramolecules by the DMA electron donor, rate
of reduction of the complex by DMA from the ³MLCT excited state, as well as
overall rate of reduction of the complex via visible light excitation. Probing a
series of complexes in detail exploring the variation of rates of important
reactions as a function of sub-unit modification provides insight into the role
of each process in the overall efficiency of water reduction to produce hydrogen.
The kinetic analysis shows that the complexes display different rates of excited
state reactions that vary with TL and halide. The role of the MLCT excited state
is elucidated by this kinetic study which shows that the ³MLCT state and not the
³MMCT is likely that key contributor to the photoreduction of these complexes.
The kinetic analysis of the excited state dynamics and reactions of the complexes
are important as this class of supramolecules behaves as photoinitiated electron
collectors and photocatalysts for the reduction of water to hydrogen.
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