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6 results on '"Lewis structure"'

1. The 'Inverted Bonds' Revisited: Analysis of 'In Silico' Models and of [1.1.1]Propellane by Using Orbital Forces

Author

Franck Fuster, François Volatron, Patrick Chaquin, Julia Contreras-García, Rubén Laplaza, University of Zaragoza - Universidad de Zaragoza [Zaragoza], Laboratoire de chimie théorique (LCT), and Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
orbital forces, 010405 organic chemistry, Organic Chemistry, Molecular orbital theory, General Chemistry, inverted bonds, 010402 general chemistry, Antibonding molecular orbital, 01 natural sciences, Catalysis, 0104 chemical sciences, Lewis structure, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Propellane, chemistry.chemical_compound, symbols.namesake, Character (mathematics), chemistry, Chemical physics, symbols, Molecule, Molecular orbital, Bond energy, [1.1.1]propellane, bond energies
Abstract

International audience; This article dwells on the nature of “inverted bonds”, which refer to the σ interaction between two sp hybrids by their smaller lobes, and their presence in [1.1.1]propellane. Firstly, we study H3C−C models of C−C bonds with frozen H‐C‐C angles reproducing the constraints of various degrees of “inversion”. Secondly, the molecular orbital (MO) properties of [1.1.1]propellane and [1.1.1]bicyclopentane are analyzed with the help of orbital forces as a criterion of bonding/antibonding character and as a basis to evaluate bond energies. Triplet and cationic states of [1.1.1]propellane species are also considered to confirm the bonding/antibonding character of MOs in the parent molecule. These approaches show an essentially non‐bonding character of the σ central C−C interaction in propellane. Within the MO theory, this bonding is thus only due to π‐type MOs (also called “banana” MOs or “bridge” MOs) and its total energy is evaluated to approximately 50 kcal mol−1. In bicyclopentane, despite a strong σ‐type repulsion, a weak bonding (15–20 kcal mol−1) exists between both central C−C bonds, also due to π‐type interactions, though no bond is present in the Lewis structure. Overall, the so‐called “inverted” bond, as resulting from a σ overlap of the two sp hybrids by their smaller lobes, appears highly questionable.

Published
2020

2. Towards Magnetic Carbo-meric Molecular Materials

Author

Faycal Allouti, Jean-Paul Malrieu, Georges Trinquier, M. Esmail Alikhani, Corentin Poidevin, Remi Chauvin, Christine Lepetit, Laboratoire de chimie de coordination (LCC), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Physicochimie des Processus de Combustion et de l’Atmosphère - UMR 8522 (PC2A), Université de Lille-Centre National de la Recherche Scientifique (CNRS), De la Molécule aux Nanos-objets : Réactivité, Interactions et Spectroscopies (MONARIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Electron pair, Spin polarization, 010405 organic chemistry, Diradical, Chemistry, Organic Chemistry, Aromaticity, General Chemistry, 010402 general chemistry, 01 natural sciences, Catalysis, 0104 chemical sciences, Lewis structure, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Delocalized electron, symbols.namesake, Computational chemistry, Phenylene, symbols, Condensed Matter::Strongly Correlated Electrons, Singlet state, Physics::Chemical Physics, ComputingMilieux_MISCELLANEOUS
Abstract

Numerous studies have underlined the putative diradical character of π-conjugated molecules that can be described by closed-shell Lewis structures, for instance, p-dimethylene p-n phenylenes, or long polyacenes. In the latter compounds, the only way to save the aromaticity of the six-membered rings is to give up the Lewis electron pairing in the singlet biradical ground state. The present work considers the possibility of doing the same by using the basic C2 units of carbo-meric architectures. A series of acyclic and cyclic carbo-meric architectures is studied by using UB3LYP DFT broken-symmetry calculations, including spin decontaminations and subsequent geometry optimization of the singlet diradical. The C2 units are shown to stabilize the singlet biradical by spin delocalization, two of them playing approximately the same role as one radical-insulating 1,4 phenylene moiety. The results are generalized to the investigation of open-shell polyradical singlet states of rigid hydrocarbon structures, the symmetry and rigidity of which can assist cooperativity and self spin polarization effect. Several synthesis targets with challenging magnetic/spin properties are suggested in the carbo-mer series.

Published
2016

3. Surprising electronic structure of the BeH- dimer: a full-configuration-interaction study

Author

Gian Luigi Bendazzoli, Marco Verdicchio, Thierry Leininger, Stefano Evangelisti, Dipartimento di Chimica, Università degli Studi di Perugia (UNIPG), Dipartimento di Chimica Fisica e Inorganica, Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Valence (chemistry), 010304 chemical physics, Chemistry, chemistry.chemical_element, Hydrogen atom, Electronic structure, Configuration interaction, 010402 general chemistry, 7. Clean energy, 01 natural sciences, 0104 chemical sciences, Lewis structure, Electronegativity, Beryllium hydride, symbols.namesake, chemistry.chemical_compound, 0103 physical sciences, Physics::Atomic and Molecular Clusters, symbols, Physics::Atomic Physics, Physics::Chemical Physics, Physical and Theoretical Chemistry, Atomic physics, Beryllium, [CHIM.OTHE]Chemical Sciences/Other
Abstract

International audience; The electronic structure of the beryllium hydride anion, BeH(-), was investigated at valence full-configuration-interaction (FCI) level, using large cc-pV6Z basis sets. It appears that there is a deep change of the wave function nature as a function of the internuclear distance: the ion structure goes from a weakly bonded Be***H(-) complex, at long distance, to a rather strongly bonded system (more than 2 eV) at short distance, having a (:Be-H)(-) Lewis structure. In this case, it is the beryllium atom that formally bears the negative charge, a surprising result in view of the fact that it is the hydrogen atom that has a larger electronegativity. Even more surprisingly, at very short distances the average position of the total electronic charge is close to the beryllium atom but on the opposite side with respect to the hydrogen position.

Published
2013

4. Hückel-Lewis Projection Method: A 'Weights Watcher' for Mesomeric Structures †

Author

Nicolas Goudard, Yannick Carissan, Denis Hagebaum-Reignier, Stéphane Humbel, Institut des Sciences Moléculaires de Marseille (ISM2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Institut de Chimie du CNRS (INC)

Subjects
010405 organic chemistry, Chemistry, Ab initio, Lewis projection, 010402 general chemistry, 01 natural sciences, 3. Good health, 0104 chemical sciences, Lewis structure, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, symbols.namesake, Computational chemistry, symbols, Physical and Theoretical Chemistry, Projection (set theory), Wave function, ComputingMilieux_MISCELLANEOUS
Abstract

A new approach to extract the coefficients and weights of Lewis structures from the Huckel wave function is designed: Huckel-Lewis projection (HL-P). The weights are obtained by projection on overlapping Lewis structures. This straightforward alternative to ab initio approaches is detailed and used on typical cases, including acrolein, allyl radical, pyrrole-like systems, and imidazolylidene. A trust parameter is defined and shown as a guide to retrieve the most important Lewis structures. The emblematic examples of butadiene and benzene are chosen to illustrate the use of this parameter.

Published
2008

5. Maximum probability domains from Quantum Monte Carlo Calculations

Author

Michel Caffarel, Anthony Scemama, Andreas Savin, Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de chimie théorique (LCT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Electron pair, 010304 chemical physics, Chemistry, Quantum Monte Carlo, General Chemistry, 010402 general chemistry, Space (mathematics), 01 natural sciences, Electron localization function, 0104 chemical sciences, Lewis structure, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Computational Mathematics, symbols.namesake, Quantum mechanics, 0103 physical sciences, symbols, Molecular orbital, Wave function, Maxima
Abstract

International audience; Although it would be tempting to associate the Lewis structures to the maxima of the squared wave function |Psi|2, we prefer in this paper the use of domains of the three-dimensional space, which maximize the probability of containing opposite-spin electron pairs. We find for simple systems (CH4, H2O, Ne, N2, C2H2) domains comparable to those obtained with the electron localization function (ELF) or by localizing molecular orbitals. The different domains we define can overlap, and this gives an interesting physical picture of the floppiness of CH5+ and of the symmetric hydrogen bond in FHF-. The presence of multiple solutions has an analogy with resonant structures, as shown in the trans-bent structure of Si2H2. Correlated wave functions were used (MCSCF or Slater-Jastrow) in the Variational Quantum Monte Carlo framework.

Published
2007

6. What Makes the Trifluoride Anion F3- So Special? A Breathing-Orbital Valence Bond ab Initio Study

Author

Philippe C. Hiberty, Benoît Braïda, Laboratoire de chimie théorique (LCT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie Physique D'Orsay (LCPO), and Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Ab initio, Trimer, Electronic structure, 010402 general chemistry, Biochemistry, 01 natural sciences, Catalysis, Dissociation (chemistry), Ion, Lewis structure, symbols.namesake, Colloid and Surface Chemistry, Computational chemistry, Single bond, 010405 organic chemistry, Chemistry, General Chemistry, General Medicine, Bond order, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Modern valence bond theory, Chemical bond, Covalent bond, Chemical physics, symbols, Valence bond theory, Ground state, Generalized valence bond
Abstract

The ground states of the F(3)(-) and H(3)(-) hypercoordinated anions are investigated and analyzed in terms of valence bond structures by means of the breathing-orbital valence bond method. While H(3)(-) is described reasonably well as the interplay of two major Lewis structures, H(2) + H(-) and its mirror image, the description of F(3)(-) requires a further structure, of the type F(*)F(-)F(*), which strongly stabilizes the trimer relative to the dissociation products, and endows the F(3)(-) ground state with a predominant three-electron bond character. It follows that the simple picture that is closest to the true nature of F(3)(-) is a resonating combination of F(2)(-) + F(*) and its mirror image. This peculiarity of the F(3)(-) electronic structure is at the origin of its preferred dissociation channel leading to F(2)(-) + F(*) rather than to the most stable product F(2) + F(-), at high collision energies. The three-electron bond character of F(3)(-) is also the root cause for the failure of the Hartree-Fock and density functional methods for this species, and for its strong tendency to artifactual symmetry-breaking. As an alternative to the Rundle-Pimentel model, the origins of the stability of F(3)(-), as opposed to the instability of H(3)(-), CH(5)(-), and other S(N)2 transition states, are analyzed in the framework of valence bond state correlation diagrams [Shaik, S.; Shurki, A. Angew. Chem., Int. Ed. 1999, 38, 586]. It is found that a fundamental factor of stability for X(3)(-) is the presence of lone pairs on the X fragment. The explanation carries over to other trihalide anions, and to isoelectronic 22-valence electron hypercoordinated anions.

Published
2004

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