I have calculated HOMO and LUMO energies for an anthraquinone derivative and the values are -9.029 eV and -6.826 eV and the HOMO-LUMO gap is found to be 2.203 eV. In some articles, I found that charge transfer in a molecule can be studied using HOMO-LUMO analysis. Anyone please explain how we can understand charge transfer from calculated values of HOMO and LUMO energies.
Dear renjith,
The HOMO-LUMO analysis cannot provide any information about charge transfer (CT). Indeed, you should center on the corresponding transition state structure (TS). In other word, when two interacting fragments are considered in the TS, CT is meaningful. You can easily perform a NPA (natural population analysis) for the optimized TS to obtain sum of atomic charges in one of TS fragments. Assume that the sum of atomic charges to be -0.23e. This negative value clearly indicates that the CT of 0.23 takes place from other fragment toward the fragment you considered.
Sincerely,
Saeed
Dear renjith,
The HOMO-LUMO analysis cannot provide any information about charge transfer (CT). Indeed, you should center on the corresponding transition state structure (TS). In other word, when two interacting fragments are considered in the TS, CT is meaningful. You can easily perform a NPA (natural population analysis) for the optimized TS to obtain sum of atomic charges in one of TS fragments. Assume that the sum of atomic charges to be -0.23e. This negative value clearly indicates that the CT of 0.23 takes place from other fragment toward the fragment you considered.
Sincerely,
Saeed
Hi,
I agree with Saeedreza. For more information about calculation of the global electron density transfer see https://dl.dropboxusercontent.com/u/37677442/tut-4-gedt-v2-en.pdf
It may be helpful - DOI: 10.1021/ja512089e J. Am. Chem. Soc. 2015, 137, 150−153.
Article Carbene-Dichlorosilylene Stabilized Phosphinidenes Exhibitin...
I would assume that what was meant in the papers was simply that one can estimate charge transfer behavior from the relative shapes/positions of the HOMO and LUMO. If the two span different regions of the molecule, then excitation of a HOMO electron into the LUMO would constitute a spatial transfer of charge. It's not the most rigorous way to approach the problem, but it provides qualitative information for minimal effort.
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