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Open AccessArticle

Interplay of Semicoordination and π-Hole Bonding: The Case of Cocrystals of Group 10 (Ni, Pd, Pt) Dithiocarbonate Complexes with 1,4-Diiodotetrafluorobenzene

by Marina A. Stozharova, Vitaly V. Suslonov, Rosa M. Gomila, Antonio Frontera and Anastasiya A. Eliseeva

Int. J. Mol. Sci. 2026, 27(8), 3668; https://doi.org/10.3390/ijms27083668 - 20 Apr 2026

Viewed by 502

Abstract

A series of Group 10 metal dithiocarbonate complexes [M(S₂COⁱPr)₂] (M = Ni 1, Pd 2, Pt 3) was prepared following procedures from the literature and cocrystallized with the ditopic σ/π-hole donor 1,4-diiodotetrafluorobenzene. Single-crystal X-ray [...] Read more.

A series of Group 10 metal dithiocarbonate complexes [M(S₂COⁱPr)₂] (M = Ni 1, Pd 2, Pt 3) was prepared following procedures from the literature and cocrystallized with the ditopic σ/π-hole donor 1,4-diiodotetrafluorobenzene. Single-crystal X-ray diffraction revealed a consistent I···S halogen bonding motif alongside a remarkable diversity in metal-involving interactions across the Ni–Pd–Pt triad. While nickel(II) exhibits strong electrophilic M···S semicoordination, the palladium(II) center displays ambiphilic behavior, and platinum(II) acts exclusively as a nucleophile via π-hole···M bonding. Comprehensive density functional theory studies, including molecular electrostatic potential (MEP) mapping, quantum theory of atoms in molecules/noncovalent interaction plot analyses, and energy decomposition analysis, were used to quantify this competitive balance. The results demonstrate that the increasing nucleophilicity from Ni to Pt, supported by shifting MEP minima and stronger π-hole stabilization energies, dictates the preference for nucleophilic over electrophilic metal-centered contact. Full article

(This article belongs to the Special Issue 25th Anniversary of IJMS: Advances in Physical Chemistry and Chemical Physics)

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78 pages, 14439 KB

Open AccessReview

Molecular Electrostatic Surface Potential: A Predictive Framework for Noncovalent Interactions and Adsorption Characteristics in Molecular Entities

by Pradeep R. Varadwaj, Helder M. Marques, Arpita Varadwaj, Ireneusz Grabowski and Koichi Yamashita

Int. J. Mol. Sci. 2026, 27(8), 3352; https://doi.org/10.3390/ijms27083352 - 8 Apr 2026

Viewed by 1332

Abstract

The molecular electrostatic surface potential (MESP) has become a key theoretical tool for probing reactivity in chemical systems. It reveals electrophilic and nucleophilic regions on molecular surfaces, underpinning the understanding of noncovalent interactions such as hydrogen, triel, tetrel, pnictogen, chalcogen, halogen, matere, and [...] Read more.

The molecular electrostatic surface potential (MESP) has become a key theoretical tool for probing reactivity in chemical systems. It reveals electrophilic and nucleophilic regions on molecular surfaces, underpinning the understanding of noncovalent interactions such as hydrogen, triel, tetrel, pnictogen, chalcogen, halogen, matere, and aerogen bonding, among many others. These interactions, driven by Coulombic attraction, govern aggregation in molecular and supramolecular systems across solid, liquid, and gas phases. MESP applications span crystal engineering, polymers, biology, catalysis, photovoltaics, and drug discovery. While limitations exist—such as the arbitrariness in defining isodensity surfaces—its impact on advancing both theoretical and applied chemical research is substantial. This review outlines the conceptual foundations of MESP and highlights its broad relevance across the chemical sciences. Full article

(This article belongs to the Special Issue 25th Anniversary of IJMS: Advances in Physical Chemistry and Chemical Physics)

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19 pages, 4273 KB

Open AccessArticle

First-Principles Modeling of Nitazoxanide Analogues as Prospective PFOR-Targeted Antibacterials

by Huda Alqahtani, Islam Gomaa, Ahmed Refaat, M. S. A. Mansour, Raiedhah A. Alsaiari and Moustafa A. Rizk

Int. J. Mol. Sci. 2025, 26(23), 11578; https://doi.org/10.3390/ijms262311578 - 28 Nov 2025

Cited by 1 | Viewed by 851

Abstract

Pyruvate:ferredoxin oxidoreductase (PFOR) is a key Achilles’ heel in anaerobic pathogens. We integrate electronic-structure calculations (DFT), cheminformatic QSAR metrics, and residue-resolved docking to distill a concise “recognition code” and translate it into practical design rules. Using nitazoxanide (Nita; ΔG_(bind) ≈ −10.0 kcal·mol [...] Read more.

Pyruvate:ferredoxin oxidoreductase (PFOR) is a key Achilles’ heel in anaerobic pathogens. We integrate electronic-structure calculations (DFT), cheminformatic QSAR metrics, and residue-resolved docking to distill a concise “recognition code” and translate it into practical design rules. Using nitazoxanide (Nita; ΔG_(bind) ≈ −10.0 kcal·mol⁻¹) as a well-established reference, productive binding requires a conserved triad: a hydrogen-bond donor addressing Thr-997 and Cys-840, a π–π stack with Phe-869, and a recurrent π–σ contact to Thr-997 that orients the scaffold. Deacetylation to tizoxanide unmasks the phenolic donor and raises local electrophilicity, yet it also slightly loosens pocket packing (−9.6 kcal·mol⁻¹). Strategic halogenation introduces a σ-hole interaction near Pro-29, tightening pose geometry without disrupting the donor network; the lead analogue yields −10.1 kcal·mol⁻¹, and two others match the reference by preserving the triad and hydrophobic belt. The result is a minimal, testable recipe—retain the phenolic donor, enforce Thr-997/Cys-840 and Phe-869, and add a calibrated halogen σ-hole—offering falsifiable predictions to surpass nitazoxanide and guiding synthesis and biophysical validation in targeted PFOR inhibition. Full article

(This article belongs to the Special Issue Cheminformatics in Drug Discovery and Green Synthesis)

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17 pages, 1865 KB

Open AccessArticle

Halogens On, H-Bonds Off—Insights into Structure Control of Dihalogenated Imidazole Derivatives

by Luca Mensing, Marcus Layh and Marian Hebenbrock

Crystals 2025, 15(11), 1000; https://doi.org/10.3390/cryst15111000 - 20 Nov 2025

Viewed by 959

Abstract

Halogen bonds play an important role in the targeted generation of solid-state structures, with polyhalogenated compounds enabling the simultaneous formation of various interactions. In this manuscript, we investigate the interactions of dihalogenated compounds in the solid state. Unlike investigated in previous studies, the [...] Read more.

Halogen bonds play an important role in the targeted generation of solid-state structures, with polyhalogenated compounds enabling the simultaneous formation of various interactions. In this manuscript, we investigate the interactions of dihalogenated compounds in the solid state. Unlike investigated in previous studies, the introduction of protective groups in these compounds prevents the formation of dominant hydrogen bonds. The structures of diiodo imidazole derivatives are compared with the analogous dibromo compounds. A total of four different protective groups (two benzylic and two oxycarbonyl protective groups) are introduced and the respective compounds are characterized by X-ray crystallography. The significance of the protective groups for the solid-state structure can be distinguished on the basis of the additional donor atoms and functional groups. It can be seen that the iodo compounds in particular are capable of forming halogen bonds and that additional structural motifs can be generated by suitable protective groups. Full article

(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals (2nd Edition))

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18 pages, 1005 KB

Open AccessPerspective

The Next Frontier in the Study of Noncovalent Bonding: Transition Metals

by Steve Scheiner

Molecules 2025, 30(17), 3643; https://doi.org/10.3390/molecules30173643 - 7 Sep 2025

Cited by 11 | Viewed by 1900

Abstract

As work continues unabated in the study of noncovalent bonding, particularly σ-hole bonds, new challenges have emerged as the participation of transition metals in interactions of this sort is fast becoming appreciated. While there are certain similarities with the halogen, chalcogen, etc, bonds, [...] Read more.

As work continues unabated in the study of noncovalent bonding, particularly σ-hole bonds, new challenges have emerged as the participation of transition metals in interactions of this sort is fast becoming appreciated. While there are certain similarities with the halogen, chalcogen, etc, bonds, in which the main group elements participate, there are certain unique properties of these metal atoms that must be analyzed before a complete understanding can be attained. As one example, these atoms tend to act simultaneously as both electron donors and acceptors, a synergistic action that amplifies the overall bond strength. Ideas are expressed in this paper to hopefully guide future work in this exciting new arena. Full article

(This article belongs to the Section Physical Chemistry)

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15 pages, 2825 KB

Open AccessArticle

Metal-Involving Bifurcated Halogen Bonding with Iodide and Platinum(II) Center

by Mariya A. Kryukova, Margarita B. Kostareva, Anna M. Cheranyova, Marina A. Khazanova, Anton V. Rozhkov and Daniil M. Ivanov

Int. J. Mol. Sci. 2025, 26(10), 4555; https://doi.org/10.3390/ijms26104555 - 9 May 2025

Cited by 6 | Viewed by 1368

Abstract

The cocrystallization of trans-[PtI₂(NCR)₂] (R = NMe₂1, NEt₂2, Ph 3, o-ClC₆H₄4) with iodine and iodoform gave the crystalline adducts 1∙4I₂, 2∙2CHI₃ [...] Read more.

The cocrystallization of trans-[PtI₂(NCR)₂] (R = NMe₂1, NEt₂2, Ph 3, o-ClC₆H₄4) with iodine and iodoform gave the crystalline adducts 1∙4I₂, 2∙2CHI₃, 3∙2CHI₃, and 4∙4I₂, whose structures were studied by single-crystal X-ray diffractometry (XRD). In the structures, apart from the rather predictable C–H⋯I hydrogen bonds (HBs) and I–I⋯I or C–I⋯I halogen bonds (XBs) with the iodide ligands, we identified bifurcated I–I⋯(I–Pt) and C–I⋯(I–Pt) metal-involving XBs, where the platinum center and iodide ligands function as simultaneous XB acceptors toward σ-holes of I atoms in I₂ or CHI₃. Appropriate density functional theory (DFT) calculations (PBE-D3/jorge-DZP-DKH with plane waves in the GAPW method) performed with periodic boundary conditions confirmed the existence of the bifurcated metal-involving I–I⋯(I–Pt) and C–I⋯(I–Pt) interactions and their noncovalent nature. Full article

(This article belongs to the Section Materials Science)

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17 pages, 5659 KB

Open AccessArticle

Supramolecular Organization of Diaryliodonium Dicyanoargentates(I) Provided by Iodine(III)–Cyanide Halogen Bonding

by Irina S. Aliyarova, Anastasiia V. Koziakova, Daniil M. Ivanov, Natalia S. Soldatova and Pavel S. Postnikov

Inorganics 2025, 13(5), 157; https://doi.org/10.3390/inorganics13050157 - 9 May 2025

Cited by 6 | Viewed by 1997

Abstract

Three diaryliodonium dicyanoargentates(I), [MesIAr][Ag(CN)₂] (Ar = Ph 1, Mes 2, 4-MeC₆H₄ 3; Mes = 2,4,6-Me₃C₆H₂), were prepared by anion metathesis. The X-ray structural analyses for these crystals revealed [...] Read more.

Three diaryliodonium dicyanoargentates(I), [MesIAr][Ag(CN)₂] (Ar = Ph 1, Mes 2, 4-MeC₆H₄ 3; Mes = 2,4,6-Me₃C₆H₂), were prepared by anion metathesis. The X-ray structural analyses for these crystals revealed C–I^III∙∙∙N≡C halogen bonds (abbreviated as XB) between I atoms of diaryliodonium cations and N atoms of cyano groups, which provide different supramolecular organization. The noncovalent nature of these interactions was studied by density functional theory (DFT) calculations and topological analysis of the electron density distribution in the framework of the quantum theory of atoms in molecules (QTAIM) at the PBE-D3/jorge-DZP-DKH level of theory both in gas phase and crystal models. The philicities of partners in these contacts were confirmed by electron localization function (ELF) projections, electron density/electrostatic potential (ED/ESP) profiles, and Hirshfeld surfaces analysis. An analysis of the available crystallographic data from the literature allows us to find other examples of σ-hole interactions including the dicyanoargentate(I) anion, and the C–X∙∙∙N≡C (X = Br, I, Te) bonding were also confirmed theoretically. Full article

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28 pages, 6488 KB

Open AccessArticle

Decrypting the Unusual Structure and σ-Hole Interactions of the XC(NO₂)₃ (X=F, Cl, Br, and I) Compounds Using Quasi-Atomic Orbitals

by Emilie B. Guidez

Molecules 2025, 30(9), 1986; https://doi.org/10.3390/molecules30091986 - 29 Apr 2025

Cited by 1 | Viewed by 1328

Abstract

This work reports the quasi-atomic orbital analysis of the XC(NO₂)₃ (X=F, Cl, Br, and I) compounds and shows that the interactions between the C-N σ bonds and the lone electron pairs on the halogen atom and oxygen atoms of the [...] Read more.

This work reports the quasi-atomic orbital analysis of the XC(NO₂)₃ (X=F, Cl, Br, and I) compounds and shows that the interactions between the C-N σ bonds and the lone electron pairs on the halogen atom and oxygen atoms of the nitro groups may contribute to the unusually short C-X distances observed. While the presence of a σ-hole on the halogen atom of the XC(NO₂)₃ compound may not be obvious from the electron density distribution, an analysis of the intermolecular forces of the NH₃--XC(NO₂)₃ complexes suggests a σ -hole interaction between the nitrogen lone pair and halogen atom X (X=Cl, Br, and I) in the linear N--X-C configuration, where electrostatics and exchange forces dominate. The linear N--X-C bond in these systems is shown to have a noticeable covalent character, which is captured in the polarization energy term. Complexation with the ammonia nucleophile is shown to affect the electronic structure of the entire compounds, notably the oxygen/halogen lone electron pairs interactions with the C-N σ bonds. Full article

(This article belongs to the Special Issue Fundamental Aspects of Chemical Bonding—2nd Edition)

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16 pages, 5488 KB

Open AccessArticle

Unraveling the Strength and Nature of Se∙∙∙O Chalcogen Bonds: A Comparative Study of SeF₂ and SeF₄ Interactions with Oxygen-Bearing Lewis Bases

by Renhua Chen, Fengying Lei, Deze Jin, Ke Peng, Qingyu Liu, Yeshuang Zhong, Liang Hong, Xiaolong Li, Zhu Zeng and Tao Lu

Molecules 2024, 29(23), 5739; https://doi.org/10.3390/molecules29235739 - 5 Dec 2024

Cited by 2 | Viewed by 1983

Abstract

Chalcogen bonds (ChBs) involving selenium have attracted substantial scholarly interest in past years owing to their fundamental roles in various chemical and biological fields. However, the effect of the valency state of the electron-deficient selenium atom on the characteristics of such ChBs remains [...] Read more.

Chalcogen bonds (ChBs) involving selenium have attracted substantial scholarly interest in past years owing to their fundamental roles in various chemical and biological fields. However, the effect of the valency state of the electron-deficient selenium atom on the characteristics of such ChBs remains unexplored. Herein, we comparatively studied the σ-hole-type Se∙∙∙O ChBs between SeF₂/SeF₄ and a series of oxygen-bearing Lewis bases, including water, methanol, dimethyl ether, ethylene oxide, formaldehyde, acetaldehyde, acetone, and formic acid, using ab initio computations. The interaction energies of these chalcogen-bonded heterodimers vary from −5.25 to −11.16 kcal/mol. SeF₂ participates in a shorter and stronger ChB than SeF₄ for all the examined heterodimers. Such Se∙∙∙O ChBs are closed-shell interactions, exhibiting some covalent character for all the examined heterodimers, except for SeF₄∙∙∙water. Most of these chalcogen-bonded heterodimers are predominantly stabilized through orbital interactions between the lone pair of the O atom in Lewis bases and the σ*(Se–F) antibonding orbitals of Lewis acids. The back-transfer of charge from the lone pair of selenium into the σ* or π* antibonding orbitals of Lewis bases is also observed for all systems. Energy decomposition analysis reveals that the electrostatic component significantly stabilizes the targeted heterodimers, while the induction and dispersion contributions cannot be ignored. Full article

(This article belongs to the Section Computational and Theoretical Chemistry)

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17 pages, 7579 KB

Open AccessArticle

Diverse Cyclization Pathways Between Nitriles with Active α-Methylene Group and Ambiphilic 2-Pyridylselenyl Reagents Enabled by Reversible Covalent Bonding

by Alexey A. Artemjev, Alexander A. Sapronov, Alexey S. Kubasov, Alexander S. Peregudov, Alexander S. Novikov, Anton R. Egorov, Victor N. Khrustalev, Alexander V. Borisov, Zhanna V. Matsulevich, Namiq G. Shikhaliyev, Valentine G. Nenajdenko, Rosa M. Gomila, Antonio Frontera, Andreii S. Kritchenkov and Alexander G. Tskhovrebov

Int. J. Mol. Sci. 2024, 25(23), 12798; https://doi.org/10.3390/ijms252312798 - 28 Nov 2024

Cited by 10 | Viewed by 2679

Abstract

Herein, we describe a novel coupling between ambiphilic 2-pyridylselenyl reagents and nitriles featuring an active α-methylene group. Depending on the solvent employed, this reaction can yield two distinct types of cationic pyridinium-fused selenium-containing heterocycles, 1,3-selenazolium or 1,2,4-selenadiazolium salts, in high yields. This is [...] Read more.

Herein, we describe a novel coupling between ambiphilic 2-pyridylselenyl reagents and nitriles featuring an active α-methylene group. Depending on the solvent employed, this reaction can yield two distinct types of cationic pyridinium-fused selenium-containing heterocycles, 1,3-selenazolium or 1,2,4-selenadiazolium salts, in high yields. This is in contrast to what we observed before for other nitriles. Notably, the formation of selenadiazolium is reversible, gradually converting into the more thermodynamically stable selenazolium product in solution. Our findings reveal, for the first time, the reversible nature of 1,3-dipolar cyclization between the CN triple bond and 2-pyridylselenyl reagents. Nitrile substitution experiments in the adducts confirmed the dynamic nature of this cyclization, indicating potential applications in dynamic covalent chemistry. DFT calculations revealed the mechanistic pathways for new cyclizations, suggesting a concerted [3 + 2] cycloaddition for the formation of selenadiazolium rings and a stepwise mechanism involving a ketenimine intermediate for the formation of selenazolium rings. Natural bond orbital analysis confirmed the involvement of σ-hole interactions and lone pair to σ* electron donation in these processes. Additionally, theoretical investigations of σ-hole interactions were performed, focusing on the selenium-centered contacts within the new compounds. Full article

(This article belongs to the Special Issue Noncovalent Interactions and Applications in Materials and Catalysis)

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13 pages, 2587 KB

Open AccessArticle

Unconventional C—Hlg···H–C (Hlg = Cl, Br, and I) Interactions Involving Organic Halides: A Theoretical Study

by Sergi Burguera and Antonio Bauzá

Molecules 2024, 29(23), 5606; https://doi.org/10.3390/molecules29235606 - 27 Nov 2024

Viewed by 1196

Abstract

In this study, unconventional C—Hlg···H–C (Hlg = Cl, Br, and I) interactions involving sp, sp², and sp³ organic halides were investigated at the RI-MP2/aug-cc-pVQZ level of theory. Energy Decomposition Analyses (EDA) and Natural Bonding Orbital (NBO) studies showed that these [...] Read more.

In this study, unconventional C—Hlg···H–C (Hlg = Cl, Br, and I) interactions involving sp, sp², and sp³ organic halides were investigated at the RI-MP2/aug-cc-pVQZ level of theory. Energy Decomposition Analyses (EDA) and Natural Bonding Orbital (NBO) studies showed that these intermolecular contacts are mainly supported by orbital and dispersion contributions, which counteracted the unfavorable/slightly favorable electrostatics due to the halogen–hydrogen σ-hole facing. In addition, the Bader’s Quantum Theory of Atoms in Molecules (QTAIM) and the Noncovalent Interaction plot (NCIplot) visual index methodologies were used to further characterize the interactions discussed herein. We expect that the results reported herein will be useful in the fields of supramolecular chemistry, crystal engineering, and rational drug design, where the fine tuning of noncovalent interactions is crucial to achieve molecular recognition or a specific solid-state architecture. Full article

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23 pages, 6068 KB

Open AccessArticle

Chalcogen Noncovalent Interactions between Diazines and Sulfur Oxides in Supramolecular Circular Chains

by Emna Rahali, Zahra Noori, Youssef Arfaoui and Jordi Poater

Int. J. Mol. Sci. 2024, 25(13), 7497; https://doi.org/10.3390/ijms25137497 - 8 Jul 2024

Cited by 4 | Viewed by 1895

Abstract

The noncovalent chalcogen interaction between SO₂/SO₃ and diazines was studied through a dispersion-corrected DFT Kohn–Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking [...] Read more.

The noncovalent chalcogen interaction between SO₂/SO₃ and diazines was studied through a dispersion-corrected DFT Kohn–Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking the capability of diazine molecules to detect SO₂/SO₃ compounds within the atmosphere. Trends in the interaction energies with the increasing number of molecules are mainly determined by the Pauli steric repulsion involved in these σ-hole/π-hole interactions. But more importantly, despite the assumed electrostatic nature of the involved interactions, the covalent component also plays a determinant role in its strength in the involved chalcogen bonds. Noticeably, π-hole interactions are supported by the charge transfer from diazines to SO₂/SO₃ molecules. Interaction energies in these supramolecular complexes are not only determined by the S···N bond lengths but attractive electrostatic and orbital interactions also determine the trends. These results should allow us to establish the fundamental characteristics of chalcogen bonding based on its strength and nature, which is of relevance for the capture of sulfur oxides. Full article

(This article belongs to the Special Issue Noncovalent Interactions and Applications in Materials and Catalysis)

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15 pages, 2340 KB

Open AccessArticle

Using Hybrid PDI-Fe₃O₄ Nanoparticles for Capturing Aliphatic Alcohols: Halogen Bonding vs. Lone Pair–π Interactions

by María de las Nieves Piña, Alberto León, Antonio Frontera, Jeroni Morey and Antonio Bauzá

Int. J. Mol. Sci. 2024, 25(12), 6436; https://doi.org/10.3390/ijms25126436 - 11 Jun 2024

Viewed by 1436

Abstract

In this study, Fe₃O₄ nanoparticles (FeNPs) decorated with halogenated perylene diimides (PDIs) have been used for capturing VOCs (volatile organic compounds) through noncovalent binding. Concretely, we have used tetrachlorinated/brominated PDIs as well as a nonhalogenated PDI as a reference system. [...] Read more.

In this study, Fe₃O₄ nanoparticles (FeNPs) decorated with halogenated perylene diimides (PDIs) have been used for capturing VOCs (volatile organic compounds) through noncovalent binding. Concretely, we have used tetrachlorinated/brominated PDIs as well as a nonhalogenated PDI as a reference system. On the other hand, methanol, ethanol, propanol, and butanol were used as VOCs. Experimental studies along with theoretical calculations (the BP86-D3/def2-TZVPP level of theory) pointed to two possible and likely competitive binding modes (lone pair–π through the π-acidic surface of the PDI and a halogen bond via the σ-holes at the Cl/Br atoms). More in detail, thermal desorption (TD) experiments showed an increase in the VOC retention capacity upon increasing the length of the alkyl chain, suggesting a preference for the interaction with the PDI aromatic surface. In addition, the tetrachlorinated derivative showed larger VOC retention times compared to the tetrabrominated analog. These results were complemented by several state-of-the-art computational tools, such as the electrostatic surface potential analysis, the Quantum Theory of Atoms in Molecules (QTAIM), as well as the noncovalent interaction plot (NCIplot) visual index, which were helpful to rationalize the role of each interaction in the VOC···PDI recognition phenomena. Full article

(This article belongs to the Collection Feature Papers in Molecular Nanoscience)

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26 pages, 16372 KB

Open AccessArticle

Halogen Bond via an Electrophilic π-Hole on Halogen in Molecules: Does It Exist?

by Pradeep R. Varadwaj

Int. J. Mol. Sci. 2024, 25(9), 4587; https://doi.org/10.3390/ijms25094587 - 23 Apr 2024

Cited by 14 | Viewed by 3350

Abstract

This study reveals a new non-covalent interaction called a π-hole halogen bond, which is directional and potentially non-linear compared to its sister analog (σ-hole halogen bond). A π-hole is shown here to be observed on the surface of halogen in halogenated molecules, which [...] Read more.

This study reveals a new non-covalent interaction called a π-hole halogen bond, which is directional and potentially non-linear compared to its sister analog (σ-hole halogen bond). A π-hole is shown here to be observed on the surface of halogen in halogenated molecules, which can be tempered to display the aptness to form a π-hole halogen bond with a series of electron density-rich sites (Lewis bases) hosted individually by 32 other partner molecules. The [MP2/aug-cc-pVTZ] level characteristics of the π-hole halogen bonds in 33 binary complexes obtained from the charge density approaches (quantum theory of intramolecular atoms, molecular electrostatic surface potential, independent gradient model (IGM-δg^inter)), intermolecular geometries and energies, and second-order hyperconjugative charge transfer analyses are discussed, which are similar to other non-covalent interactions. That a π-hole can be observed on halogen in halogenated molecules is substantiated by experimentally reported crystals documented in the Cambridge Crystal Structure Database. The importance of the π-hole halogen bond in the design and growth of chemical systems in synthetic chemistry, crystallography, and crystal engineering is yet to be fully explicated. Full article

(This article belongs to the Special Issue Noncovalent Interactions: New Developments in Experiment and Theory)

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14 pages, 2268 KB

Open AccessArticle

Triel Bonds between BH₃/C₅H₄BX and M(MDA)₂ (X = H, CN, F, CH₃, NH₂; M = Ni, Pd, Pt, MDA = Enolated Malondialdehyde) and Group 10 Transition Metal Electron Donors

by Xin Wang, Zhihao Niu, Sean A. C. McDowell and Qingzhong Li

Molecules 2024, 29(7), 1602; https://doi.org/10.3390/molecules29071602 - 3 Apr 2024

Cited by 6 | Viewed by 2063

Abstract

A systematic theoretical study was conducted on the triel bonds (TrB) within the BH₃∙∙∙M(MDA)₂ and C₅H₄BX∙∙∙M(MDA)₂ (M = Ni, Pd, Pt, X = H, CN, F, CH₃, NH₂, MDA = enolated [...] Read more.

A systematic theoretical study was conducted on the triel bonds (TrB) within the BH₃∙∙∙M(MDA)₂ and C₅H₄BX∙∙∙M(MDA)₂ (M = Ni, Pd, Pt, X = H, CN, F, CH₃, NH₂, MDA = enolated malondialdehyde) complexes, with BH₃ and C₅H₄BX acting as the electron acceptors and the square-coordinated M(MDA)₂ acting as the electron donor. The interaction energies of these systems range between −4.71 and −33.18 kcal/mol. The larger the transition metal center M, the greater the enhancement of the TrB, with σ–hole TrBs found to be stronger than π–hole TrBs. In the σ–hole TrB complex, an electron-withdrawing substituent on the C opposite to the B atom enhances the TrB, while an electron-donating substituent has little effect on the strength of TrB in the Pd and Pt complexes but enhances the TrB in the Ni-containing complexes. The van der Waals interaction plays an important role in stabilizing these binary systems, and its contribution diminishes with increasing M size. The orbital effect within these systems is largely due to charge transfer from the d_z² orbital of M into the empty p_z orbital of B. Full article

(This article belongs to the Special Issue Multiconfigurational and DFT Methods Applied to Chemical Systems—2nd Edition)

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