Highly Efficient Ultrafast Electron Injection from the Singlet MLCT Excited State of Copper(I) Diimine Complexes to TiO₂ Nanoparticles

Abstract

Cu‐Komplex als Photosensibilisator: Die Dynamik eines photoinduzierten Ladungstransfers von einem Kupfer(I)‐Diimin‐Komplex auf TiO2‐Nanopartikel wurde mit einer Kombination aus mehreren zeitauflösenden Spektroskopiemethoden untersucht. Ein effizienter und sehr schneller Elektronentransfer aus dem MLCT‐Singulettzustand resultiert aus einer Verzerrung der tetraedrischen Koordinationsumgebung und den sperrigen Gruppen an den Liganden.

Photoinduced Structural Dynamics of Molecular Systems Mapped by Time-Resolved X-ray Methods

“…Indeed, upon transfer of an electron to the ligand, a significant structural change from a tetrahedral geometry to a flat one occurs (Figure 10a). Chen and co-workers [172][173][174] investigated the structure of the MLCT states of such complexes, in particular ([CuI(dmp)2] + (dmp=2,9-dimethyl-1,10-phenanthroline)), by ps XAS. Upon 400 nm photoexcitation, one reaches the S2 state, which decays on an ultrafast time scale to the S1 state 172,[175][176][177] followed by relaxation to the T1 state.…”

“…As far as metal-based sensitizers are concerned, several groups have investigated the change of oxidation state of the metal upon MLCT excitation of the dye and injection into the substrate. 166,174 but the fate of the electron in the substrate was not investigated. The first study of the electron injection with element-selective probing of both the sensitizer and the substrate was carried out by the Chergui group on Ruthenium dyes adsorbed on anatase TiO2 nanoparticles (NPs) and compared with the results of band gap excitation of bare NPs.…”

New insight into metalloporphyrin excited state structures and axial ligand binding from X-ray transient absorption spectroscopic studies

“…In carbmonoxy Mb, the low spin Fe(II) is bound in a pseudo octahedral configuration by the porphyrin nitrogens, an axial histidine (His 93), and CO, a strong field ligand [82,83]. On excitation of the porphyrin Soret or Q bands, a hole in the porphyrin orbital is generated that leads to a subsequent metal to ligand charge transfer and photolysis [82].…”

“…A preliminary study by the Chergui group [90,91] With an energy range covering both the XANES and EXAFS portions of the iron K-edge, we were able to investigate both electronic changes in the Mb metal center, such as the rearrangement of the d-level energies and occupancy, and minute structural changes in the iron heme [83]. The deoxy, carbon monoxy, and metmyoglobin (oxidized Fe(III) heme) have progressively higher energy edge energies due to the decreasing electron density on iron, allowing the dynamics of photolysis and recombination to be monitored at Fe edge (Fig.…”

“…In an effort to understand the influence of the protein on determining heme structural dynamics following photolysis, we have conducted parallel XTA studies of photo-initiated CO dissociation in both Mb [83] and its active site cofactor, iron protoporphyrin IX (FePP) [87].…”