NTO and hole-electron analysis of an ICT-containing molecule

mulutas

Hello everyone, I'm conducting excited-state analyses of a molecule I believe has an ICT mechanism using Gaussian 16. Furthermore, as far as I know, ICT occurs in the excited state, not the ground state. Please correct me if I'm wrong. My goal is to determine whether intramolecular charge transfer (ICT) occurs in the molecule. To do this, I first optimized the S0 geometry and ran a td-dft using it (please let me know if there's anything wrong with my work so far). Then, I extracted the NTO orbitals as specified on the Gaussian16 website. I'm very confused about what to do next. I also extracted hole-particle images using the fchk file I obtained from the NTO analysis. These images clearly show electron movements. The hole is in the donor region, and the particle is delocalized and evenly distributed throughout the molecule. What do you think I can interpret?

wal

Based on your description, it seems that the system has already demonstrated the occurrence of ICT. You may try using Multiwfn's IFCT analysis to quantitatively determine how much charge is transferred between fragments during excitation.

sobereva

Note that NTO is not always applicable. It is very often that there is no dominant NTO pair. I strongly suggest using hole-electron analysis in Multiwfn, see Section 4.18.1 of Multiwfn manual for illustrative example. In addition, as mentioned by wal, IFCT of Multiwfn can easily quantify amount of charge transfer, see Section 4.18.8 of Multiwfn maunal for example.