Local structure of photoexcited bimetallic complexes refined by quantitative XANES analysis

Computational characterization of competing energy and electron transfer states in bimetallic donor-acceptor systems for photocatalytic conversion

“…saturated hydrocarbon linker groups used as molecular bridges in the common donor-bridge-acceptor (D-B-A) fashion, 55 modeling the donor and acceptor units as decoupled is generally applicable and a very good model to a first approximation, since the weakly bound interaction can be captured as a weak perturbation of the independent D and A states where the D-A interaction strength decays exponentially with D-A separation. This was also clearly seen in our recent study where a non-interacting unbound system (Ru|Co), where each center was relaxed separately, was able to reproduce the excited state landscape of the combined weakly bound (Ru–Co) 10 complex. 12 Thus, in weakly bound systems, a first order approximation of the interplay between structural and electronic factors involved can be constructed from the various mononuclear relaxed excited states.…”

“…Co(III)). Covalently linked bimetallic complexes have been used extensively to experimentally investigate electron transfer properties of donor (D)-acceptor (A) systems 6–7 including studies of bridged Ru(II)-Co(III) systems 8–10 as well as theoretical intermolecular electron transfer studies. 11–12 The complicated excited state dynamics which depend on both structural and electronic effects are frequently further complicated by solvent interactions and/or coupling between the electronic and nuclear processes, making these processes difficult to study.…”

“…Donor-acceptor interactions have been widely studied and range from very weak to very strong, as nicely illustrated in the series of unbound (Ru|Co), weakly bound (Ru–Co), and tightly bound (Ru=Co) supramolecular Ru(II)-Co(III) systems studied by us and others. 10, 12 ET kinetics of many (D|A) unbound systems consisting of two transition metal centers in solution have also been extensively studied as a classic example of Marcus 51 type ET. In linked D-A systems, the chemical nature of the linker group is of key importance, and there have been numerous investigations of D-A interactions with different linker groups from early work by Newton and others.…”

Pump-Flow-Probe X-ray Absorption Spectroscopy as a Tool for Studying Intermediate States of Photocatalytic Systems

“…Figure 5 shows that both methods produce similar difference spectra; a small difference of the width of the first peak is however discernible and could be due to the mixing of intermediates with different concentration ratios in these two spectra. The shape of the spectra is typical for Co reduction (see for example ref 48 and figures S4 and S5 in the SI). The first peak corresponds to the shift of the edge position to lower energy due to the oxidation state change of Co and partially due to the structural changes in the molecule.…”

Supramolecular Hemicage Cobalt Mediators for Dye‐Sensitized Solar Cells

“…[51] Recently,s uch calculations have been used to predict the photoinduced cascade of model Ru-Co systems, accurately reproducing the excited-state landscape, which results in af inal reduced Co II . [52] The Co III singlet, triplet, and quintet as well as the Co II doublet and quartet geometries of each complex were freely optimized using PBE0, which is known to give good agreement to experimental structures, [53][54][55] and at riple-z 6-311G(d,p) basis set with acomplete acetonitrile polarizable continuum model (PCM) in Gaussian G09. [44] Each minimum is characterized by spin, energy,a nd the selected structural parameters, R,w hich characterizes the average Co-ligand bond distances, and Oo ro ctrahedricity factor which is the root mean squared error of the Co-ligand angles (a perfect octahedron is O % 08).…”