Variational Energy Decomposition Analysis of Charge-Transfer Interactions between Metals and Ligands in Carbonyl Complexes

Jingting Han, Adam Grofe, Jiali Gao

Research output: Contribution to journalArticlepeer-review

Abstract

Variational energy decomposition analyses have been presented to quantify the σ-dative, ligand-to-metal forward charge transfer (CT) and the π-conjugative, metal-to-ligand backward charge delocalization on a series of isolelectronic transition-metal carbonyl complexes M(CO)6, including M = Ti2-, V-, Cr, Mn+, and Fe2+. Although the qualitative features of these energy terms are understood, well-defined quantitative studies have been scarce. Consistent with early findings, electrostatic and Pauli exchange effects play a key role in σ-donation, resulting in blue shifts in ligand vibrational frequency in the complex geometries. Excluding chemical bonding interactions between the CO ligand and the metal fragments in the energy decomposition analysis, we found that loosely bound electrostatic complexes can be formed at a longer metal-to-ligand distance due to the exponential decay of Pauli exchange. In all complexes, the overall binding stabilization can be attributed to CT effects, with opposing trends between σ-donation and π-back bonding that follows an order of Ti2-(4.4) > V1-(2.6) > Cr (1.5) > Mn1+(1.1) > Fe2+(0.5) in π-to-σ CT ratio. These electronic and energetic features are mirrored in the vibrational frequency shifts induced by different factors. The present investigation may help stimulate the use of energy decomposition techniques to understand the structure and activity of metallocatalysts using density functional theory.

Original languageEnglish (US)
Pages (from-to)14060-14071
Number of pages12
JournalInorganic chemistry
Volume60
Issue number18
DOIs
StatePublished - Sep 20 2021

Bibliographical note

Funding Information:
This work was supported in part by the Shenzhen Municipal Science and Technology Innovation Commission (grant KQTD2017-0330155106581) and the National Natural Science Foundation of China (grant no. 21533003). A.G. has been a recipient of an International Postdoctoral Fellowship of China.

Publisher Copyright:
© 2021 American Chemical Society

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