| 1. |
- Bonn, Annabell G., et al.
(författare)
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Photoinduced Electron Transfer in an Anthraquinone-[Ru(bpy)(3)](2+)-Oligotriarylamine-[Ru(bpy)(3)](2+)-Anthraquinone Pentad
- 2016
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 55:6, s. 2894-2899
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Tidskriftsartikel (refereegranskat)abstract
- A molecular pentad comprised of a central multielectron donor and two flanking photosensitizer-acceptor moieties was prepared in order to explore the possibility of accumulating two positive charges at the central donor, using visible light as an energy input. Photoinduced charge accumulation in purely molecular systems without sacrificial reagents is challenging, because of the multitude of energy-wasting reaction pathways that are accessible after excitation with two photons. As expected, the main photoproduct in our pentad is a simple electron hole pair, and it is tricky to identify the desired two-electron oxidation product on top of the stronger signal resulting from one-electron oxidation.
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| 2. |
- Dongare, Prateek, et al.
(författare)
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Analysis of Hydrogen-Bonding Effects on Excited-State Proton-Coupled Electron Transfer from a Series of Phenols to a Re(I) Polypyridyl Complex
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 121:23, s. 12569-12576
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Tidskriftsartikel (refereegranskat)abstract
- In the present study of proton-coupled electron transfer (PCET) reactions, the excited-state of a fac-[(CO)(3)Re-I(bpy)(4,4'-bpy)](+) (bpy = 2,2'-bipyridine and 4,4'-bpy = 4,4'-bipyridine) complex was reductively quenched by a series of phenols. A variation of substituents on the phenols substantially alters their pK(a) and E degrees values and provides an opportunity to study photoinduced PCET as a function of their redox properties. Analyses of absorption spectral changes indicate that the phenols form a weak hydrogen bond with the pyridinic nitrogen of the 4,4'-bpy ligand in the ground-state, and ground-state association, constant (K-A) values were determined. This H-bonded adduct quenches the excited Re complex by PCET from the phenol, to form the reduced and,protonated Re complex. The KA values-obtained aid quantitative evaluation of the rate constant for the PCET reaction in the H-bonded, adduct. Thus, photophysical studies and Mechanistic analysis indicate that the reaction occurs via a concerted mechanistic pathway, for the unsubstituted phenol and phenols with electron-withdrawing subtituents. Furthermore; the magnitude of the quenching varies systematically with the proton-coupled potentials of the phenols and not their hydrogen-bonding strength (as reflected in K-A). This study is one of the first detailed analyses of intermolecular H-bonding between a self-assembling metal complex and a series of substituted phenols in an effort to study their relationship with the kinetic parameters in a photoinduced CPET reaction.
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