5
$\begingroup$

I am looking for an easy to calculate model system in which I could see a ligand metal charge transfer. Basically I am looking for a model complex, that might have the metal/ligand in different oxidation states: $\ce{ M^{III}(Lig)}$ versus $\ce{M^{II}(Lig^{\bullet +})}$ or $\ce{M^{IV}(Lig^{\bullet -})}$. I am calling it a charge transfer since I am not sure how else to call it.
I am also quite aware, that the description of these systems is necessarily a multireference case, so ordinary DFT methods will fail. (At least broken symmetry is necessary.)

In principle I was thinking about an iron heme complex that might exhibit that feature.
iron(II)heme vs iron(III)heme.-
However, I have the feeling, that this kind of system is already pretty demanding to calculate the electronic structure. Since I would like to use it as an exercise and for a tutorial achieving alternative occupations I would prefer a much simpler case. It should eventually treated with broken symmetry DFT and CAS/MR methods.

Does anyone know of such a system or would suggest one. It does not have to be a real one. Purely hypothetical is just as fine.

$\endgroup$
3
$\begingroup$

AFAIK, permanganate ion is colored because of intense line, corresponding to oxygene-manganese charge transfer. This is noted in wikipedia article on charge-transer complex, but, unfortunately, without quote, and I'm unable to come with one right now

Edit: Aha. Here there is a MO diagram on $\ce{MnO4-}$ ion and extensive discussion of (mis)understanding of its spectra, including statement I made above.

$\endgroup$
  • $\begingroup$ Well that certainly looks very promising and thank you very much for the reference. I will definitely have a deeper look into it next week - I am at home now and have no access to the paper, but the abstract sounds like a system worth considering. $\endgroup$ – Martin - マーチン Dec 6 '14 at 8:11
0
$\begingroup$

you can try $\ce{Cu^{2+}--Cys}$ vs $\ce{Cu^+--Cys}$, much smaller and it is a model of $\ce{Cu-S}$ clusters in eg $\ce{Cu}$-binding proteins

I'm interested in these systems too, maybe we can share information?

Goedele

$\endgroup$
  • $\begingroup$ Thank you very much for the suggestion. I will have a closer look at that. It might be suitable for my purpose, since it is organometallic chemistry. You state that it is used as a model for copper binding proteins, do you have any reference for that statement? I would like to read up more about that. $\endgroup$ – Martin - マーチン Dec 6 '14 at 8:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.