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Topic: Interpreting uv-vis spectra  (Read 171 times)

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Offline Timu

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Interpreting uv-vis spectra
« on: March 11, 2021, 11:06:10 AM »
Hello everyone,
during my last lab course I synthesized cis-[RuCl2(DMSO)4]. Now I need to analyze it's uv-vis spectrum.
I was asked to assign electronic transitions to the absorption bands but since I haven't had my uv-vis lecture yet, I have trouble doing so. The spectrum is attached.

The bands are at 306 nm (ε = 357 L/mol*cm) and 360 nm (ε = 503 L/mol*cm) with CHCl3 as solvent.

I know that the d-configuration is low spin d6 and that three of the DMSO molecules bond via S (π-acceptor) and one via O (δ-donor), the Cl ligands are π-donors. So I think CT's in the form of π :rarrow: d and vice versa should be possible. I have read, though, that CT transitions have values of ε >1000.

d :rarrow: d transitions could occur as well but the example I have seen had lower ε values (below 200), so I am not sure whether they would be visible here.

A third option would be n :rarrow: π/δ transitions.

These are my thoughts, but I'm still not sure which transition fits which band since my ε values don't seem to fit except maybe for n :rarrow: π/δ transitions

Help would be much appreciated.

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