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A detailed understanding of the dynamics of photoinduced processes occurring in the electronic excited state is essential in informing the rational design of photoactive transition metal complexes. Here, the rate of intersystem crossing in a Cr(III)-centred spin-flip emitter is directly determined through the use of ultrafast broadband fluorescence upconversion spectroscopy (FLUPS). In this contribution, we combine 1,2,3-triazole-based ligands with a Cr(III) centre and report the solution-stable complex [Cr(btmp)2]3+ (btmp = 2,6-bis(4-phenyl-1,2,3-triazol-1-yl-methyl)pyridine) (13+) which displays near infrared (NIR) luminescence at 760 nm (τ = 13.7 µs, ϕ = 0.1%) in fluid solution. The excited state properties of 13+ are probed in detail through a combination of ultrafast transient absorption (TA) and femtosecond-to-picosecond FLUPS. Although TA spectroscopy allows us to observe the evolution of phosphorescent excited states within the doublet manifold, more significantly and for the first time for a complex of Cr(III), we utilise FLUPS to capture the short-lived fluorescence from initially populated quartet excited states immediately prior to the intersystem crossing process. The decay of fluorescence from the low-lying 4MC state therefore allows us to assign a value of (823 fs)-1 to the rate of intersystem crossing. Importantly, the sensitivity of FLUPS to only luminescent states allows us to disentangle the rate of intersystem crossing from other closely associated excited state events, something which has not been possible in the spectroscopic studies previously reported for luminescent Cr(III) systems.
|Number of pages||12|
|Journal||Journal of the American Chemical Society|
|Early online date||24 May 2023|
|Publication status||E-pub ahead of print - 24 May 2023|
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- 1 Invited talk
Photoactive Triazolyl Coordination Complexes: A Journey from Photochemistry to Sustainable Luminescent Materials
Claire Bakewell (Speaker), Paul Scattergood (Speaker) & Alice Johnson (Speaker)16 Nov 2022
Activity: Talk or presentation types › Invited talk