Ultrafast photo-induced ligand solvolysis of cis-[Ru(bipyridine)(2)(nicotinamide)(2)](2+): experimental and theoretical insight into its photoactivation mechanism

Simon E. Greenough, Gareth M. Roberts*, Nichola A. Smith, Michael D. Horbury, Russell G. McKinlay, Justyna M. Zurek, Martin J. Paterson, Peter J. Sadler, Vasilios G. Stavros

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)
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Abstract

Mechanistic insight into the photo-induced solvent substitution reaction of cis-Pu(bipyridine)(2)(nicotinamide)(2)](2+) (1) is presented. Complex 1 is a photoactive species, designed to display high cytotoxicity following irradiation, for potential use in photodynamic therapy (photochemotherapy). In Ru(m) complexes of this type, efficient population of a dissociative triplet metal-centred ((MC)-M-3) 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 [Ru(bipyridine)(2)(nicotinamide)(H2O)](2+) (2). Following irradiation of 1, a thorough kinetic picture is derived from ultrafast UV/Vis transient absorption spectroscopy measurements, using a 'target analysis' approach, and provides both timescales and quantum yields for the key processes involved. We show that photoactivation of 1 to 2 occurs with a quantum yield >0.36, all within a timeframe of 400 ps. Characterization of the excited states involved, particularly the nature of the PCI and how it undergoes a geometry relaxation to accommodate the water ligand, which is a keystone in the efficiency of the photoactivation of 1, is accomplished through state-of-the-art computation including complete active space self-consistent field methods and time-dependent density functional theory. Importantly, the conclusions here provide a detailed understanding of the initial stages involved in this photoactivation and the foundation required for designing more efficacious photochemotherapy drugs of this type.

Original languageEnglish
Pages (from-to)19141-19155
Number of pages15
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number36
DOIs
Publication statusPublished - 2014

Keywords

  • RUTHENIUM POLYPYRIDYL COMPLEXES
  • DENSITY-FUNCTIONAL THEORY
  • EXCITED-STATE EVOLUTION
  • LIGHT-EMITTING DEVICES
  • PHOTOSUBSTITUTION REACTIONS
  • PHOTOCHEMICAL DISSOCIATION
  • CONICAL INTERSECTIONS
  • PHOTODYNAMIC THERAPY
  • FEMTOSECOND DYNAMICS
  • RELAXATION DYNAMICS

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