X-ray transient absorption structural characterization of the 3MLCT triplet excited state of cis-[Ru(bpy)2(py)2]2+

Abstract

The excited state dynamics and structure of the photochemically active complex cis-[Ru(bpy)2(py)2](2+) have been investigated using optical transient absorption (OTA) and X-ray transient absorption (XTA) spectroscopy, and density functional theory (DFT). Upon light-excitation in aqueous solution cis-[Ru(bpy)2(py)2](2+) undergoes ultrafast dissociation of one pyridine ligand to form cis-[Ru(bpy)2(py)(H2O)](2+). OTA measurements highlighted the presence of two major time components of 1700 ps and 130 ps through which the system decays to the ground-state and evolves towards the photoproduct. XTA data were acquired after 150 ps, 500 ps, and 3000 ps from laser excitation (λexc = 351 nm) and provided the transient structure of the (3)MLCT state corresponding to the longer time component in the OTA experiment. In excellent agreement with DFT, XTA shows that the (3)MLCT geometry is characterized by an elongation of the dissociating Ru-N(py) bond and a shortening of the trans Ru-N(bpy) bond with respect to the ground state. Conversely, calculations show that the (3)MC state has a highly distorted structure with Ru-N(py) bonds between 2.77-3.05 Å.

Redox-active and DNA-binding coordination complexes of clotrimazole

“…In the case of 3 and 7, their X-ray structures were previously solved [17] and the calculated geometries display a good agreement with them, although bond distances and angles are somewhat overestimated by calculations as demonstrated previously for other systems [33].…”

Combatting AMR: photoactivatable ruthenium(ii)-isoniazid complex exhibits rapid selective antimycobacterial activity

“…This technique has previously provided a detailed understanding of the pathways involved in photoactivation of this type of Ru II complex. 21,22 Efficient population of a dissociative triplet metal-centered ( 3 MC) state is key to generating high quantum yields of a penta-coordinate intermediate (PCI) species, which in turn may form the target species: a mono-aqua photoproduct. We showed that photoactivation of cis -[Ru(bpy) 2 (NA) 2 ] 2+ to cis -[Ru(bpy) 2 (NA) (H 2 O)] 2+ (NA = nicotinamide) occurs with a quantum yield ≥0.36, all within a timeframe of ∼400 ps.…”

Synchrotron ultrafast techniques for photoactive transition metal complexes

“…We determined the 3 MLCT ES structure of cis-[Ru(bpy) 2 (py) 2 ] 2+ and complemented our previous TR-XSS characterization with a 100 ps resolution TR-EXAFS experiment performed at the 11-ID-D beamline of the APS (see §4d) [283].…”