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Bonfim VSA, Souza CP, de Oliveira DAB, Baptista L, Santos ACF, Fantuzzi F. Deciphering the irradiation induced fragmentation-rearrangement mechanisms in valence ionized CF3CH2F. J Chem Phys 2024; 160:124308. [PMID: 38526111 DOI: 10.1063/5.0188201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/27/2024] [Indexed: 03/26/2024] Open
Abstract
The increasing presence of 1,1,1,2-tetrafluoroethane (CF3CH2F) in the atmosphere has prompted detailed studies into its complex photodissociation behavior. Experiments focusing on CF3CH2F irradiation have unveiled an array of ions, with the persistent observation of the rearrangement product CHF2+ not yet fully understood. In this work, we combine density functional theory, coupled-cluster calculations with a complete basis set formalism, and atom-centered density matrix propagation molecular dynamics to investigate the energetics and dynamics of different potential pathways leading to CHF2+. We found that the two-body dissociation pathway involving an HF rearrangement, which was previously considered complex for CHF2+ formation, is actually straightforward but not likely due to the facile loss of HF. In contrast, our calculations reveal that the H elimination pathway, once thought of as a potential route to CHF2+, is not only comparably disadvantageous from both thermodynamic and kinetic points of view but also does not align with experimental data, particularly the lack of a rebound peak at m/z 101-102. We establish that the formation of CHF2+ is predominantly via the HF elimination channel, a conclusion experimentally corroborated by studies involving the trifluoroethylene cation CF2CHF+, a key intermediate in this process.
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Affiliation(s)
- Víctor S A Bonfim
- School of Chemistry and Forensic Science, University of Kent, Canterbury CT2 7NH, United Kingdom
- Instituto de Física, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, 21941-909 Rio de Janeiro, Brazil
| | - Cauê P Souza
- School of Chemistry and Forensic Science, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - Daniel A B de Oliveira
- Universidade Federal do Norte do Tocantins, Lot. Araguaína Sul, 77826-612 Araguaína, Brazil
| | - Leonardo Baptista
- Departamento de Química e Ambiental, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra km 298, 27537-000 Rio de Janeiro, Brazil
| | - Antônio C F Santos
- Instituto de Física, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, 21941-909 Rio de Janeiro, Brazil
| | - Felipe Fantuzzi
- School of Chemistry and Forensic Science, University of Kent, Canterbury CT2 7NH, United Kingdom
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2
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Seijas LE, Almeida R, Rincón L, Zambrano C, Rodríguez V, Merino G, Torres FJ. Revisiting the bonding of the pentagonal-pyramidal C 6H 62+ and C 6(CH 3) 62+ dications. Phys Chem Chem Phys 2023. [PMID: 38018412 DOI: 10.1039/d3cp04247b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
This work delves into the bonding nature of the pentagonal-pyramidal benzene and hexamethylbenzene dications, C6R62+ (R = H and CH3), which contain a hexacoordinate carbon. The study employs a range of methodologies to analyze a series of scalar fields, including electron density, electron localization function, local momentum representation, and the evaluation of the Coulomb hole through information theory-derived functions. The findings unveil that electron density undergoes transfer from the pentagonal ring to the apical group. As a result, the base of the complex accumulates the positive charge. Moreover, an extended electron density domain emerges between the carbon pentagon and the apical carbon atom. This phenomenon is related to the molecular orbitals with a dipolar character aligned with the principal axis of the molecule. The results also indicate an electron density polarization towards the apical carbon, coupled with an exclusion of electron density surrounding both the apical carbon and the lower portion of the pentagonal ring. These provide valuable insights into the complex bonding nature of hexacoordinate carbon and its implications for organic chemistry.
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Affiliation(s)
- Luis E Seijas
- Escuela de Ingeniería Ciencia y Tecnología, Universidad del Rosario, Bogotá 11171, Colombia
| | - Rafael Almeida
- Laboratorio de Procesos Dinámicos en Química, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101, Venezuela
| | - Luis Rincón
- Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, Ecuador
| | - Cesar Zambrano
- Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, Ecuador
| | - Vladimir Rodríguez
- Departamento de Matemática, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, Ecuador
| | - Gabriel Merino
- Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Física Aplicada, Km. 6 Antigua carretera a Progreso Apdo. Postal 73, Cordemex, 97310 Merida, Mexico
| | - F Javier Torres
- Escuela de Ingeniería Ciencia y Tecnología, Universidad del Rosario, Bogotá 11171, Colombia
- Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, Ecuador
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Long-lived molecular dications: A selected probe for double ionization. ADVANCES IN QUANTUM CHEMISTRY 2022. [DOI: 10.1016/bs.aiq.2022.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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de Sousa DWO, Nascimento MAC. Three-center two-electron bonds from the quantum interference perspective. Phys Chem Chem Phys 2022; 24:15958-15972. [DOI: 10.1039/d2cp00841f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nature of the three-center two-electron (3c2e) chemical bond is investigated by the Interference Energy Analysis (IEA) method and using of a SC(2, 3) (spin coupled wave function with two...
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Guerra C, Kumar S, Aguilar-Galindo F, Díaz-Tendero S, Lozano AI, Mendes M, Limão-Vieira P, García G. Unexpected benzene oxidation in collisions with superoxide anions. Sci Rep 2021; 11:23125. [PMID: 34848760 PMCID: PMC8633363 DOI: 10.1038/s41598-021-02408-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 11/16/2021] [Indexed: 12/02/2022] Open
Abstract
Superoxide anions colliding with benzene molecules at impact energies from 200 to 900 eV are reported for the first time to form massive complexes. With the aid of quantum chemistry calculations, we propose a mechanism in which a sudden double ionization of benzene and the subsequent electrostatic attraction between the dication and the anion form a stable covalently bonded C6H6O2+ molecule, that evolves towards the formation of benzene-diol conformers. These findings lend support to a model presenting a new high energy anion-driven chemistry as an alternative way to form complex molecules.
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Affiliation(s)
- Carlos Guerra
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006, Madrid, Spain
| | - Sarvesh Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
| | - Fernando Aguilar-Galindo
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018, Donostia-San Sebastián, Spain
| | - Sergio Díaz-Tendero
- Departamento de Química, Universidad Autónoma de Madrid, Módulo 13, 28049, Madrid, Spain.
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049, Madrid, Spain.
- Institute for Advanced Research in Chemical Science (IAdChem), Universidad Autónoma de Madrid, 28049, Madrid, Spain.
| | - Ana I Lozano
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
| | - Mónica Mendes
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006, Madrid, Spain.
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
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Nascimento MAC. The Valence-Bond (VB) Model and Its Intimate Relationship to the Symmetric or Permutation Group. Molecules 2021; 26:molecules26154524. [PMID: 34361677 PMCID: PMC8347111 DOI: 10.3390/molecules26154524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/06/2021] [Accepted: 07/10/2021] [Indexed: 11/16/2022] Open
Abstract
VB and molecular orbital (MO) models are normally distinguished by the fact the first looks at molecules as a collection of atoms held together by chemical bonds while the latter adopts the view that each molecule should be regarded as an independent entity built up of electrons and nuclei and characterized by its molecular structure. Nevertheless, there is a much more fundamental difference between these two models which is only revealed when the symmetries of the many-electron Hamiltonian are fully taken into account: while the VB and MO wave functions exhibit the point-group symmetry, whenever present in the many-electron Hamiltonian, only VB wave functions exhibit the permutation symmetry, which is always present in the many-electron Hamiltonian. Practically all the conflicts among the practitioners of the two models can be traced down to the lack of permutation symmetry in the MO wave functions. Moreover, when examined from the permutation group perspective, it becomes clear that the concepts introduced by Pauling to deal with molecules can be equally applied to the study of the atomic structure. In other words, as strange as it may sound, VB can be extended to the study of atoms and, therefore, is a much more general model than MO.
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de Sousa DWO, Nascimento MAC. Substituent Effects on the Quantum Interference of Two-Center One-Electron Bonds: [B 2X 6] - (X = H, F, Cl, CN, OH, CH 3, and OCH 3). J Phys Chem A 2021; 125:4558-4564. [PMID: 34014679 DOI: 10.1021/acs.jpca.1c02771] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interference energy analysis (IEA) provided by the generalized product function energy partitioning (GPF-EP) method was applied to investigate the influence of the neighboring atoms on the nature of the two-center one-electron (2c1e) bonds in the anion dimers of BX3 species (X = H, F, Cl, CN, OH, CH3, and OCH3). The species were studied at the GVB-PP(6/12).SC(1,2)/6-31**G++ level of calculation. The IEA has revealed that there is a balance between two main factors determining the chemical stability of the species. Quantum interference acts as the sole stabilizing effect in the formation of the chemical bonds, particularly as the result of the drop in kinetic energy, and the electronegativity of the substituent has a direct influence on the magnitude of this effect. The quasi-classical energy is responsible for the destabilizing factors, mainly the group bulkiness, and the "electron-withdrawing" effect in the case of the cyano group.
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Wolff W, Perlin A, Oliveira RR, Fantuzzi F, Coutinho LH, de A Ribeiro F, Hilgers G. Production of Long-Lived Benzene Dications from Electron Impact in the 20-2000 eV Energy Range Combined with the Search for Global Minimum Structures. J Phys Chem A 2020; 124:9261-9271. [PMID: 33079556 DOI: 10.1021/acs.jpca.0c07931] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work, we report a systematic search of metastable C6Hn2+ (n = 1-6) dications from electron impact time-of-flight measurements of several benzene derivatives in combination with global minimum search based on the genetic algorithm. Our theoretical calculations reveal that the C6Hn2+ (n < 6) global minimum structures are completely different from that of the benzene dication, featuring linear carbon chains and/or cyclopropenylium moieties. Experimentally, the doubly charged species were investigated for a wide range of electron impact energies, from 20 to 2000 eV, for benzene and several monosubstituted compounds containing either electron-withdrawing or -donating groups. Furthermore, the C6Hn2+ production, evaluated from the yields of the dications with respect to that of the parent ion (or parent dication), was compared to those obtained from charge exchange in the doubly charged 2E spectra and electron impact experiments available in the literature. The yields of the long-lived benzene dications were contrasted to those analogues formed in chlorobenzene. Moreover, the formation of C6Hn2+ species is strongly dependent on the nature of substituent groups, with electron-withdrawing ones favoring the dication formation.
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Affiliation(s)
- Wania Wolff
- Physics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
| | - Amir Perlin
- Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
| | - Ricardo R Oliveira
- Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
| | - Felipe Fantuzzi
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, 97074 Würzburg, Germany
| | - Lucia H Coutinho
- Physics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
| | | | - Gerhard Hilgers
- Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany
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Pozo-Guerron P, Seijas LE, Burgos JL, Rincon L, Torres FJ, Mora JR, Zambrano C, Almeida R. A topological study of the haxacoordinated carbon in the pentagonal-pyramidal benzene and hexamethylbenzene dications. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137912] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Three-center two-electron bonds in the boranes B2H6 and B3H8− from the quantum interference perspective. Theor Chem Acc 2020. [DOI: 10.1007/s00214-020-02654-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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11
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de Sousa DWO, Nascimento MAC. One-electron bonds are not "half-bonds". Phys Chem Chem Phys 2019; 21:13319-13336. [PMID: 31184654 DOI: 10.1039/c9cp02209k] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite the success of the molecular orbital (MO) and valence-bond (VB) models to describe the electronic structure and properties of molecules, neither MO nor VB provides an explanation for the nature of the chemical bond. The first to address this problem was Ruedenberg, who showed that chemical bonds result from quantum interference. He developed a method to calculate the interference contribution to the total electronic energy and density and applied it to molecules containing typical two-centre two-electron (2c-2e) covalent bonds. To test the generality of Ruedenberg's hypothesis, we developed a powerful Interference Energy Analysis (IEA) method to calculate the interference contributions of individual chemical bonds to the total energy of diatomic and polyatomic molecules, and showed that any two-electron bond, despite its polarity, results from quantum interference. Nevertheless, many stable molecules are experimentally known whose chemical structures clearly indicate the existence of two-centre one-electron bonds (2c-1e). Therefore, the question remains if quantum interference will be the dominant effect for these systems. This work describes the extension of the IEA for treating two-centre one-electron bonds, making use of a Generalised Product Function (GPF) built from spin coupled wave functions of N electrons in M orbitals, SC(N,M). Several diatomic and polyatomic molecules were analysed and whenever possible the results were compared with the analogous case of a two-electron bond. The results indicate that interference is the dominant effect for the one-electron bonds, which reinforces the role of quantum interference as the central element in chemical bonding theory.
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Affiliation(s)
- David Wilian Oliveira de Sousa
- Instituto de Química, Universidade Federal do Rio de Janeiro Cidade Universitária, CT Bloco A Sala 412, Rio de Janeiro, RJ 21941-909, Brazil.
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Klein JEMN, Havenith RWA, Knizia G. The Pentagonal-Pyramidal Hexamethylbenzene Dication: Many Shades of Coordination Chemistry at Carbon. Chemistry 2018; 24:12340-12345. [PMID: 29341342 PMCID: PMC6120489 DOI: 10.1002/chem.201705812] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Indexed: 12/15/2022]
Abstract
A recent report on the crystal structure of the pentagonal-pyramidal hexamethylbenzene dication C6 (CH3 )62+ by Malischewski and Seppelt [Angew. Chem. Int. Ed. 2017, 56, 368] confirmed the structural proposal made in the first report of this compound in 1973 by Hogeveen and Kwant [Tetrahedron Lett. 1973, 14, 1665]. The widespread attention that this compound quickly gained led us to reinvestigate its electronic structure. On the basis of intrinsic bond orbital analysis, effective oxidation state analysis, ring current analysis, and comparison with well-established coordination complexes, it is demonstrated that the central carbon atom behaves like a transition metal. The central (apical) carbon atom, although best described as a highly Lewis-acidic carbon atom coordinated with an anionic cyclopentadienyl ligand, is also capable of acting as an electron-pair donor to a formal CH3+ group. The different roles of coordination chemistry are discussed.
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Affiliation(s)
- Johannes E. M. N. Klein
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Science and EngineeringUniversity of GroningenNijenborgh 49747AG GroningenThe Netherlands
| | - Remco W. A. Havenith
- Zernike Institute for Advanced Materials and Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747AG GroningenThe Netherlands
- Ghent Quantum Chemistry Group, Department of Inorganic and Physical ChemistryGhent UniversityKrijgslaan 281 (S3)9000GentBelgium
| | - Gerald Knizia
- Department of ChemistryPennsylvania State University401A Chemistry Bldg; University ParkPA16802USA
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Fantuzzi F, Rudek B, Wolff W, Nascimento MAC. Doubly and Triply Charged Species Formed from Chlorobenzene Reveal Unusual C–Cl Multiple Bonding. J Am Chem Soc 2018. [DOI: 10.1021/jacs.7b12749] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Felipe Fantuzzi
- Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil
| | - Benedikt Rudek
- Physikalisch-Technische Bundesanstalt, Bundesallee
100, 38116 Braunschweig, Germany
| | - Wania Wolff
- Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-972, Brazil
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14
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Hydrogenated Benzene in Circumstellar Environments: Insights into the Photostability of Super-hydrogenated PAHs. ACTA ACUST UNITED AC 2018. [DOI: 10.3847/1538-4357/aaa977] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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15
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Forgy CC, Schlimgen AW, Mazziotti DA. Effects of nitrogenous substituent groups on the benzene dication. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1430386] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- C. C. Forgy
- Department of Chemistry and the James Franck Institute, The University of Chicago, Chicago, IL, USA
| | - A. W. Schlimgen
- Department of Chemistry and the James Franck Institute, The University of Chicago, Chicago, IL, USA
| | - D. A. Mazziotti
- Department of Chemistry and the James Franck Institute, The University of Chicago, Chicago, IL, USA
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Fantuzzi F, Cardozo TM, Nascimento MAC. On the metastability of doubly charged homonuclear diatomics. Phys Chem Chem Phys 2018; 19:19352-19359. [PMID: 28703821 DOI: 10.1039/c7cp02792c] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Generalized valence bond (GVB) and spin-coupled (SC) calculations were used in conjunction with the generalized product function energy partitioning (GPF-EP) method to describe the origin of metastability in doubly charged homonuclear dications. A model to describe the formation of metastable potential wells based on interference and quasi-classical effects is presented. The GPF-EP picture of dications is the result of polarization-aided strong covalent bonding surpassing Coulomb electrostatic repulsion. Important differences in the quasi-classical density profiles of He22+ and Ne22+ reveal the underlying mechanism that could lead to bound or unbound states. Finally, the nature of the chemical bond of N22+, O22+, and F22+ is described. The results suggest that the ground states of the mentioned dications are bounded and that the depth of the potential wells of these exotic species is related to the interference effect, in the same way as in previously studied neutral molecules.
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Affiliation(s)
- Felipe Fantuzzi
- Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil.
| | - Thiago M Cardozo
- Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil.
| | - Marco A C Nascimento
- Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil.
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Sousa DWOD, Nascimento MAC. Are One-Electron Bonds Any Different from Standard Two-Electron Covalent Bonds? Acc Chem Res 2017; 50:2264-2272. [PMID: 28786664 DOI: 10.1021/acs.accounts.7b00260] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The nature of the chemical bond is perhaps the central subject in theoretical chemistry. Our understanding of the behavior of molecules developed amazingly in the last century, mostly with the rise of quantum mechanics (QM) and QM-based theories such as valence bond theory and molecular orbital theory. Such theories are very successful in describing molecular properties, but they are not able to explain the origin of the chemical bond. This problem was first analyzed in the 1960s by Ruedenberg, who showed that covalent bonds are the direct result of quantum interference between one-electron states. The generality of this result and its quantification were made possible through the recent development of the generalized product function energy partitioning (GPF-EP) method by our group, which allows the partitioning of the electronic density and energy into their interference and quasi-classical (noninterference) contributions. Furthermore, with GPF wave functions these effects can be analyzed separately for each bond of a molecule. This interference energy analysis has been applied to a large variety of molecules, including diatomics and polyatomics, molecules with single, double, and triple bonds, molecules with different degrees of polarity, linear or branched molecules, cyclic or acyclic molecules, conjugated molecules, and aromatics, in order to verify the role played by quantum interference. In all cases the conclusion is exactly the same: for each bond in each of the molecules considered, the main contribution to its stability comes from the interference term. Two-center one-electron (2c1e) bonds are the simplest kind of chemical bonds. Yet they are often viewed as odd or unconventional cases of bonding. Are they any different from conventional (2c2e) bonds? If so, what differences can we expect in the nature of (2c1e) bonds relative to electron-pair bonds? In this Account, we extend the GPF-EP method to describe bonds involving N electrons in M orbitals (N < M) and show its application to (2c1e) bonds. As examples we chose the molecules H2+, H3C·CH3+, B2H4-, [Cu·BH3(PH3)3], and an alkali-metal cation dimer, and we evaluated the components of the electronic energy and density, which account for the formation of the bond, and compared the results with those for the respective analogous molecules exhibiting the "conventional" two-electron bond. In all cases, it was verified that interference is the dominant effect for the one-electron bonds. The GPF-EP results clearly indicate that molecules exhibiting (2c1e) bonds should not be considered as special systems, since one- and two-electron bonds result from quantum interference and therefore there is no conceptual difference between them. Moreover, these results show that quantum interference provides a way to unify the chemical bond concept.
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Affiliation(s)
- David Wilian Oliveira de Sousa
- Instituto de Química, Universidade Federal do Rio de Janeiro Cidade Universitária, CT Bloco
A Sala 412, 21941-909 Rio de Janeiro-RJ, Brazil
| | - Marco Antonio Chaer Nascimento
- Instituto de Química, Universidade Federal do Rio de Janeiro Cidade Universitária, CT Bloco
A Sala 412, 21941-909 Rio de Janeiro-RJ, Brazil
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