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The Role of Exchange Energy in Modeling Core-Electron Binding Energies of Strongly Polar Bonds

by Feng Wang and Delano P. Chong

Molecules 2025, 30(13), 2887; https://doi.org/10.3390/molecules30132887 - 7 Jul 2025

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Accurate determination of carbon core-electron binding energies (C1s CEBEs) is crucial for X-ray photoelectron spectroscopy (XPS) assignments and predictive computational modeling. This study evaluates density functional theory (DFT)-based methods for calculating C1s core-electron binding energies (CEBEs), comparing three functionals—PW86x-PW91c (DFTpw), mPW1PW, and PBE50—across 68 C1s cases in small hydrocarbons and halogenated molecules (alkyl halides), using the delta self-consistent field ΔSCF (or ΔDFT) method developed by one of the authors over the past decade. The PW86x-PW91c functional achieves a root mean square deviation (RMSD) of 0.1735 eV, with improved accuracy for polar C-X bonds (X=O, F) using mPW1PW and PBE50, reducing the average absolute deviation (AAD) to ~0.132 eV. The study emphasizes the role of Hartree–Fock (HF) exchange in refining CEBE predictions and highlights the synergy between theoretical and experimental approaches. These insights lay the groundwork for machine learning (ML)-driven spectral analysis, advancing materials characterization, and catalysis through more reliable automated XPS assignments. Full article

(This article belongs to the Topic Theoretical, Quantum and Computational Chemistry—2nd Edition)

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18 pages, 5941 KB

Open AccessArticle

Crystal Structure and Solid-State Packing of 4-Chloro-5H-1,2,3-dithiazol-5-one and 4-Chloro-5H-1,2,3-dithiazole-5-thione

by Christos P. Constantinides, Maria Koyioni, Fadwat Bazzi, Maria Manoli, Daniel B. Lawson and Panayiotis A. Koutentis

Molecules 2021, 26(19), 5875; https://doi.org/10.3390/molecules26195875 - 28 Sep 2021

Cited by 3 | Viewed by 2511

Abstract

The crystal structure and solid-state packing of 4-chloro-5H-1,2,3-dithiazol-5-one and two polymorphs of 4-chloro-5H-1,2,3-dithiazole-5-thione were analyzed and compared to structural data of similar systems. These five-membered S,N-rich heterocycles are planar with considerable bond localization. All three structures demonstrate tight solid-state packing without voids which is attributed to a rich network of short intermolecular electrostatic contacts. These include S^δ+…N^δ−, S^δ+…O^δ−, S^δ+…Cl^δ− and S^δ+…S^δ− interactions that are well within the sum of their van der Waals radii (∑_VDW). B3LYP, BLYP, M06, mPW1PW, PBE and MP2 were employed to calculate their intramolecular geometrical parameters, the Fukui condensed functions to probe their reactivity, the bond order, Bird Index and NICS(1) to establish their aromaticity. Full article

(This article belongs to the Special Issue Polysulfur- and Sulfur-Nitrogen Heterocycles)

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19 pages, 2499 KB

Open AccessArticle

DFT Protocol for EPR Prediction of Paramagnetic Cu(II) Complexes and Application to Protein Binding Sites

by Giuseppe Sciortino, Giuseppe Lubinu, Jean-Didier Maréchal and Eugenio Garribba

Magnetochemistry 2018, 4(4), 55; https://doi.org/10.3390/magnetochemistry4040055 - 3 Dec 2018

Cited by 37 | Viewed by 8926

Abstract

With the aim to provide a general protocol to interpret electron paramagnetic resonance (EPR) spectra of paramagnetic copper(II) coordination compounds, density functional theory (DFT) calculations of spin Hamiltonian parameters g and A for fourteen Cu(II) complexes with different charges, donor sets, and geometry were carried out using ORCA software. The performance of eleven functionals was tested, and on the basis of the mean absolute percent deviation (MAPD) and standard deviation (SD), the ranking of the functionals for A_z is: B3LYP > B3PW91 ~ B3P86 > PBE0 > CAM-B3LYP > TPSSh > BH and HLYP > B2PLYP > MPW1PW91 > ω-B97x-D >> M06; and for g_z is: PBE0 > BH and HLYP > B2PLYP > ω-B97x-D > B3PW91~B3LYP~B3P86 > CAM-B3LYP > TPSSh~MPW1PW91 >> M06. With B3LYP the MAPD with respect to

A_{z}^{\exp t l}

is 8.6% with a SD of 4.2%, while with PBE0 the MAPD with respect to

g_{z}^{\exp t l}

is 2.9% with a SD of 1.1%. The results of the validation confirm the fundamental role of the second order spin-orbit contribution to A_z. The computational procedure was applied to predict the values of g_z and A_z of the adducts formed by Cu(II) with albumin and two fragments of prion protein, 106–126 and 180–193. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Late Professor Samiran Mitra)

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