Hello,
I'm trying to run a DFT simulation with G09W(Gaussian 09) in order to simulate the transition state of single-electron transfer between two organic molecules.
I've done some searching through web, but I couldn't get much info on how to draw the initial guess of such transition state, and which functional+basis set is best for such reaction.
My reaction condition is below
1 anionic organic molecule + 1 neutral organic molecule with halide
-> (single electron transfer from anion to halide molecule) -> 1 halide anion + 2 organic molecules with neutral radical on carbon
would there be any reference paper that I can refer to?
or please let me know if you have any experience of this kind of situation...
thanks :)
It is quite tricky to calculate electron transfer using DFT. Generally, to my knowledge, there are two possible ways: either you can use constrained DFT (CDFT in QChem or NWChem) to directly locate charge on either part of your system, or you can use TD-DFT as charge transfer state will be an excited state with respect to your reference system (in this case you should analyse calculated excited states to deduce which one is your target state)
Dear Eunsoo,
It is difficult to say without knowing the details of your system but depending of what do you want to do, you have several alternatives.
If your initial state is a singlet and your final state is a triplet, you can compute the minimum energy crossing point using the MECP program package of J. Harvey, that works with Gaussian09. You can also estimate the rate of the electron transfer using Marcus Theory (although in your case is not recommended since you have a large reorganization on the system).
The last possibility is to find the transition state on the open-shell singlet electronic state. It is quite tricky, but still posible. We compute a very similar system here (Ni(O) + PhI to form Ni(I)-I Ph·):
http://onlinelibrary.wiley.com/doi/10.1002/chem.201702331/full
You can find in the supporting info of the paper the MECP and Marcus theory references in case you need them.
Best,
Ignacio
Dear Ignacio,
Thank you very much for your kind answer and amazing paper of yours.
Actually I do have few questions about your work
In your paper, the transition state of single electron transfer from Ni(0) to Ar-X, the angle between Ni-X-Ar seems to be somewhere near 120'C.
Is it the optimized angle resulted from the optimization process(berny)? Also, I'm quite curious about your initial guess with the TS(bond angle, distance between reacting atoms & molecules...etc) before the optimization process, and the logic(why) of initial guess structure set-up(If you have also guessed the angle b/w Ni-X-Ar to be 120'C, I want to know why..).
I'm also trying to draw my initial guess structure for TS, which involves single electron transfer, but I'm having hard time deciding the approaching angle, and distance... etc.
Also if I'm trying to optimize the transition state of electron transfer from R-C(-) to R-I, after drawing the transition state like...
R-C- - - I- - - R, should I set the spin state as singlet or triplet before the job submission? It's quite tricky since the initial spin state is singlet(since it's reaction between anion and neutral organic molecule), but the resulted reaction products are I(-), 2R` (radicals), and the whole system will have total triplet spin state.
Once again, thank you very much...
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