Electronic and Molecular Structure of Photoexcited [Ru^II(bpy)₃]²⁺Probed by Picosecond X-ray Absorption Spectroscopy

Abstract

L(2,3) X-ray absorption spectra of aqueous [Ru(II)(bpy)3]2+ have been recorded in its ground and excited states, 50 ps after short pulse laser excitation. Significant changes in both the XANES (X-ray Near-Edge Absorption Structure) and the EXAFS (Extended X-ray Absorption Fine Structure) regions of the excited state complex are detected. The XANES line shapes have been quantitatively simulated using a crystal field multiplet code in trigonal symmetry. In addition, spectral changes in the EXAFS region of both ground and excited states are analyzed in order to extract structural parameters of their corresponding molecular structures. We obtain a Ru-N bond contraction by approximately 0.03 angstroms in the excited-state complex, as compared to the ground-state compound. This contraction results from electrostatic and polarization contributions, limited by steric constraints on the bpy ligands.

Synchrotron ultrafast techniques for photoactive transition metal complexes

“…They extended the capabilities of the previously developed fitting procedure MXAN [161] (based on a full multiple-scattering analysis [151]) to deal directly with differential XANES data. The method was successfully tested for the analysis of ps L 3 -edge XANES of [Ru(bpy) 3 ] 2+ in water solution, excited by a 400 nm ultrashort laser pulse [148,162].…”

“…For instance, the MLCT state structure of [Cu(dmp)] 2+ in acetonitrile [149,246,247] and the structural changes resulting from an intramolecular electron-transfer process in [Ru(bpy) 3 ] 2+ [148,162] were elucidated. Furthermore, TR-XAS spectroscopy has been employed to study the structural distortions in the triplet ESs of two binuclear Pt-complexes, i.e.…”

“…producing vacancies in the 3d z2 orbitals, resulting in a substantial increase of the axial-ligated photoproduct concentration. The triplet 3 MLCT electronic and molecular structure of the prototypic complex [Ru(bpy) 3 ] 2+ has been successfully probed by Chergui and co-workers [162] by TR-XAS at the L 2 -and L 3 Ru-edges. Excitation of the visible MLCT band of [Ru(bpy) 3 ] 2+ leads, after efficient intersystem crossing, to the formation of the 3 MLCT state, which then decays to the GS non-radiatively through several ESs (among which a metal-centred state) and radiatively with a luminescence lifetime of ca 600 ns, as shown in figure 10a, left-hand panel.…”

Electronic structure of Fe- vs. Ru-based dye molecules

“…4 and 7-11. For three-dimensional complexes, the electronic structure [12][13][14][15][16][17] and charge transfer [18][19][20][21][22][23][24] have been investigated using many spectroscopic [25][26][27][28][29][30][31] and theoretical [32][33][34][35][36][37][38][39][40] methods.…”

New Developments in Charge Transfer Multiplet Calculations: Projection Operators, Mixed-Spin States and π-Bonding

“…In contrast a diverse range of systems shows a small leading peak at the L 2 edge, which can be explained from the combined action of 3d(4d) spin-orbit coupling and a trigonal distortion. Systems that show this effect include Fe III (tacn) 2 , Fe III (CN) 6 [3], Ru III (bpy) 2 [4], but also oxides including the low spin Co IV system Na x CoO 2 [5].…”