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sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

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Determination of pure CT state of D-A complex

Recently a Multiwfn user asked a question

How to identify the pure charge transfer (CT) states between donor-acceptor molecule by NTO analysis?

It is reported by M. -Y Li et al. (attached herewith) that the NTO analysis has been performed to examine the electronic excitation characteristics comprehensively to gain the pure CT states.

I think my reply is also useful for some other Multiwfn users, therefore I paste my reply here

If after forming NTO analysis for an excited state, you find there is a single NTO-pair having contribution almost 100% (or at least higher than 85%), and the two NTOs almost purely locate on the donor part and acceptor part, respectively, then you can say this is a pure CT state.

In my opinion, a much better way is performing IFCT analysis, see Section 3.21.8 of Multiwfn manual for theory introduction and 4.18.8 for example. You can find two fragment, one corresponds to donor part and another one corresponds to acceptor part. Assume the amount of net charge transfer from donor to acceptor is higher than e.g. 0.85, you can the percentage of CT character of 85%, or you can even identify this is a pure CT state.