The ultrafast relaxation of aqueous iron(II)−tris(bipyridine) upon excitation into the singlet metal-to-ligand charge-transfer band (1MLCT) has been characterized by femtosecond fluorescence up-conversion and transient absorption (TA) studies. The fluorescence experiment shows a very short-lived broad 1MLCT emission band at ∼600 nm, which decays in ≤20 fs, and a weak emission at ∼660 nm, which we attribute to the 3MLCT, populated by intersystem crossing (ISC) from the 1MLCT state. The TA studies show a short-lived (<150 fs) excited-state absorption (ESA) below 400 nm, and a longer-lived one above 550 nm, along with the ground-state bleach (GSB). We identify the short-lived ESA as being due to the 3MLCT state. The long-lived ESA decay and the GSB recovery occur on the time scale of the lowest excited high-spin quintet state 5T2 lifetime. A singular value decomposition and a global analysis of the TA data, based on a sequential relaxation model, reveal three characteristic time scales:  120 fs, 960 fs, and ...

Ultrafast Nonadiabatic Dynamics of [FeII(bpy)3]2+ in Solution

http://www.nccr-must.ch/libraries.files/Light-induced_spin_crossover_in_FeII-based_complexes_The_full_photocycle_unraveled_by_ultrafast_optical_and_X-ray_spectroscopies_Nov2011.pdf

Light-induced spin crossover in Fe(II)-based complexes: The full photocycle unraveled by ultrafast optical and X-ray spectroscopies

In this contribution, we highlight the state of the art in the determination of structures with ultrafast electrons and X-rays. We provide our perspectives and reflections on the principles, techniques and methods, and on applications from different disciplines, with some focus on physical, chemical and biological structures. Although this article is not a survey of all the work done with these techniques, it provides a comprehensive referencing to current research.

Electron and X‐Ray Methods of Ultrafast Structural Dynamics: Advances and Applications

Tryptophan is commonly used to study protein structure and dynamics, such as protein folding, as a donor in fluorescence resonant energy transfer (FRET) studies. By using ultra-broadband ultrafast two-dimensional (2D) spectroscopy in the ultraviolet (UV) and transient absorption in the visible range, we have disentangled the excited state decay pathways of the tryptophan amino acid residues in ferric myoglobins (MbCN and metMb). Whereas the more distant tryptophan (Trp7) relaxes by energy transfer to the heme, Trp14 excitation predominantly decays by electron transfer to the heme. The excited Trp14→heme electron transfer occurs in

http://science.sciencemag.org/content/sci/339/6127/1586.full.pdf

Ultrafast tryptophan-to-heme electron transfer in myoglobins revealed by UV 2D spectroscopy.

This perspective presents some recent results concerning ultrafast intramolecular relaxation processes in metal-based molecular complexes. Ultrafast electronic/vibrational relaxation at sub-vibrational time scales, ultrafast intersystem crossing processes and ultrafast structure changes are discussed, stressing the questions that still need to be solved in order to arrive at a rationale that describes these processes. We will also discuss some new techniques, based on core-level spectroscopies that can provide new insights into the ultrafast intramolecular relaxation in these systems.

Alejandro Gonzalez-Gonzalez

Papers

Time-resolved visible and infrared study of the Cyano complexes of Myoglobin and of Hemoglobin I from Lucina pectinata