Unveiling ultrafast dynamics in bridged bimetallic complexes using optical and X-ray transient absorption spectroscopies

Abstract

In photosynthetic systems employing multiple transition metal centers, the properties of charge-transfer states are tuned by the coupling between metal centers.

Femtosecond Extreme Ultraviolet Spectroscopy of an Iridium Photocatalyst Reveals Oxidation State and Ligand Field Specific Dynamics

“…This reduction in the blueshift is consistent with density functional theory calculations showing that approximately half of the excess charge on the Ir is lost as the 3 MLCT state relaxes from its Franck–Condon geometry (Table S2). We note that similar core-level shifts were observed in transient L-edge XANES of iridium and osmium complexes. ,,,− …”

“…Finally, we note that in the MLCT state the core → e g 1 transition could create either a singlet or a triplet e g 2 state, resulting in a splitting of the core → e g absorption peaks. In practice, this splitting is small enough that it is not observed in either this work or in transient L-edge XANES of Ir and Os complexes. ,,,− …”

Effect of electronic structure of energy transfer in bimetallic Ru(ii)/Os(ii) complexes

“…Notably, changes in emission intensity are evident when Ru(II) or Os(II) are coordinated with Ru(II) monometallic complexes to form the corresponding Ru(II)/Ru(II), Ru(II)/Os(II), and Os(II)/Ru(II) dinuclear complexes. [8][9][10][11][12] Herein, photoinduced electron and energy transfer of Os(II)/Ru(II) dinuclear complexes with a covalent linkage are discussed with a comparison of the emission intensities and lifetimes of monometallic Ru(II) and bimetallic Ru(II)/Ru(II) and Os(II)/Ru(II) complexes. 13 The bridging ligand plays a significant role in the interaction between the metal units of the Os(II)/Ru(II) complexes.…”

Femtosecond extreme ultraviolet spectroscopy of an iridium photocatalyst reveals oxidation state and ligand field specific dynamics

“…In practice, this splitting is small enough that it is not observed in either this work or in transient L-edge XANES of Ir and Os complexes. 61,66,67,[73][74][75][76][77] The effective oxidation state change from Ir(III) to Ir(IV) lowers the energy of the core orbitals, which will result in a blueshift of the core → e g transitions. For the N 6,7 edge, this shift manifests as the derivative-shaped features between 63 and 74 eV.…”

“…We note that similar corelevel shifts were observed in transient L-edge XANES of iridium and osmium complexes. 61,66,67,[73][74][75][76][77] A different explanation must be invoked for the ~16 ps loss of intensity of the core → t 2g hole features, as these are induced absorption features that are not present in the ground state. Given the breadth of the absorption and the noise in the spectrum, the intensity of these peaks are not expected to be sensitive to the small core-level shifts that led to large changes in the derivative-shape core → e g peaks.…”