The nature of metal-ligand interactions in different metalloporphyrin · · · hydrogen cyanide complexes: Limitations of DFT exchange-correlation functionals.
Year: 2026
Type: preprint
Abstract: The weak intermolecular interaction energies of various metalloporphyrin (MP, M = Cr, Fe, Co, Ni, Zn) and hydrogen cyanide complexes along the axial metal-ligand bond have been computed using different wavefunction-based theoretical level (MP2, CCSD and CCSD(T)). The domain-based local pair natural orbital (DLPNO) method was applied at all three theoretical levels, as well as in the case of the MP2 theory, the spin-component and spin-opposite scaled frameworks were also taken into account. The nature of the interactions was analyzed by decomposing the intermolecular interaction energy into physically meaningful components (Electrostatic, Exchange, Dispersion, Non-dispersion and Perturbative triple) using the local energy decomposition (LED) method in the framework of the CCSD(T) theory. The potential energy curves were also compared with the results obtained using density functional theory ((DFT), considering sets of widely used exchange-correlation (XC) functionals, as well as the r2SCAN functional family. The behavior of DFT functionals is highly heterogeneous. For dispersion-dominant Ni, Zn and Mg cases of the interaction, the functionals underestimate the potential energy curves obtained by the CCSD and CCSD(T) methods. For the less dispersion-dominant Fe and Cr cases, where larger non-dispersion and triple perturbation (T) contributions were obtained, however, they overestimate the reference potential energy curves. This under-and overestimation can be linked to the exact exchange and correlation term used in the XC functional. Employing the MP2based component with a higher weight makes the XC functional’s behavior much more balanced. Overall, it was found that, the CAM-B3LYP, Pr2SCAN69, and our newly defined SCS1-r2SCAN0-2 (or r2SCAN0-2*, where the initail “SOS” form was replaced with “SCS”) functionals showed the most efficient performance.
Source: ChemRxiv
Authors: Alex-Adrian Farcaş, Attila Bende
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213298494