From: 2023-03-15 11:00 to 12:00
Place: Lecturehall KC:G
Contact: petter [dot] persson [at] teokem [dot] lu [dot] se

A joint Chemical Physics/ Theoretical Chemistry seminar by Professor Paul O.P. Elliott, University of Huddersfield, United Kingdom.

Title: Detection of Ru(II) & Os(II) photodechelated species and vibrationally coherent population of a Ru(II) ³MC state by ultrafast transient absorption spectroscopy

Abstract: Metal-centred (MC) states are of the utmost relevance to transition metal photophysics as parasitic excited states responsible for deactivation of emissive metal-to-ligand charge transfer (MLCT) states and in mediating photochemical ligand release reactivity. Often very short-lived and spectroscopically dark, direct study of these MC state is problematic. We have designed a series of hexatriazole-based group 8 metal complexes to explore the excited state potential energy surface ³MC region landscape. We have previously reported the complexes [M(ttzm)₂]²⁺ (ttzm = p-anisolyltris(1,2,3-triazol-4-yl)methane; M = Fe, Ru, Os) but report here transient absorption studies. Whilst the Fe(II) complex exhibits typical formation of ⁵MC state (t = 3.3 ns), the Ru(II) & Os(II) analogues both undergo dechelation on the ps timescale to yield (pseudo)pentacoodinate species which reform the ground state on the ns to ms timescale (M = Ru, t = 44 ns; M = Os, t = 7 ms). Interestingly, the complex [Ru(btz)₃]²⁺ (btz = 4,4’-bi-1,2,3-triazolyl) exhibits a Frank-Condon T₁ state of ³MC state character. Upon excitation, oscillations are observed up to 2 ps (n = 156 cm^-1) for a coherent wave packet as the initially formed and highly compressed ³MC state undergoes geometric relaxation before returning to the ground state (t = 42 ps). These results represent a rare example of accessible Os(II) ³MC states and the first, to our knowledge, example of observed vibrationally coherent Ru(II) ³MC state population.

Lecturehall KC:G