Reactivity and Structure of the 5-Dehydro-<i>m</i>-xylylene Anion

Munsch, Tamara E.; Slipchenko, Lyudmila V.; Krylov, Anna I.; Wenthold, Paul G.

doi:10.1021/jo049555t

Cited by 18 publications

(27 citation statements)

References 58 publications

(79 reference statements)

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“…Similarly, 5‐dehydro‐1,3‐quinodimethane (DMX) is a triradical with an open‐shell doublet ground state because it combines parallel spin alignment between two benzylic π‐SOMOs of MX with their antiparallel coupling to a ring σ‐SOMO of α,3‐DHT . The dominant product of electron attachment to DMX is a rare triplet carbanion . Topologically different isomers of DMX II and III with nondisjoint NBMOs have high‐spin (quartet) ground states (Figure ) .…”

Section: Fluctuating Ground‐state Multiplicitymentioning

confidence: 99%

Theory and practice of uncommon molecular electronic configurations

Gryn’ova

Coote

Corminbœuf

2015

WIREs Comput Mol Sci

100

112

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The electronic configuration of the molecule is the foundation of its structure and reactivity. The spin state is one of the key characteristics arising from the ordering of electrons within the molecule's set of orbitals. Organic molecules that have open-shell ground states and interesting physicochemical properties, particularly those influencing their spin alignment, are of immense interest within the up-and-coming field of molecular electronics. In this advanced review, we scrutinize various qualitative rules of orbital occupation and spin alignment, viz., the aufbau principle, Hund's multiplicity rule, and dynamic spin polarization concept, through the prism of quantum mechanics. While such rules hold in selected simple cases, in general the spin state of a system depends on a combination of electronic factors that include Coulomb and Pauli repulsion, nuclear attraction, kinetic energy, orbital relaxation, and static correlation. A number of fascinating chemical systems with spin states that fluctuate between triplet and open-shell singlet, and are responsive to irradiation, pH, and other external stimuli, are highlighted. In addition, we outline a range of organic molecules with intriguing non-aufbau orbital configurations. In such quasi-closed-shell systems, the singly occupied molecular orbital (SOMO) is energetically lower than one or more doubly occupied orbitals. As a result, the SOMO is not affected by electron attachment to or removal from the molecule, and the products of such redox processes are polyradicals. These peculiar species possess attractive conductive and magnetic properties, and a number of them that have already been developed into molecular electronics applications are highlighted in this review. How to cite this article:WIREs Comput Mol Sci 2015Sci , 5:440-459. doi: 10.1002Sci /wcms.1233 INTRODUCTIONT he electronic configuration and state of a molecule characterize the distribution of electrons across the corresponding one-electron wavefunctions, i.e., orbitals. 1 This model description, albeit approximate, is nonetheless indispensable in explaining and predicting molecular geometry and various chemical and physical properties. As orbitals comprise not only the spatial component, but also the spin, they also give rise to such key features as the nature of configuration shell-open or closed-and the multiplicity of the electronic state. While the majority of stable organic molecules have a closed-shell singlet ground state, species with unpaired electrons display unique chemical reactivity and are capable of carrying magnetism and conductivity functionalities. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Although historically the latter have been the domain of metals and, in particular, transition metal complexes, in the recent years the focus has ...

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Section: Fluctuating Ground‐state Multiplicitymentioning

confidence: 99%

Theory and practice of uncommon molecular electronic configurations

Gryn’ova

Coote

Corminbœuf

2015

WIREs Comput Mol Sci

100

112

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“…Currently, the term “distonic” is widely accepted and used to denote ions with formally separated charge and radical sites even if they do not fall into the formal definition. 7 According to the conventional valence bond description, the charge and radical sites are on adjacent atoms in α-distonic ions while they are separated by one and two atoms in β- and γ-distonic ions, respectively. A vast amount of experimental and theoretical studies were dedicated to distonic ions from the 1980’s to 1990’s, which have been previously reviewed separately by Hammerum and Kenttämaa.…”

Section: Introductionmentioning

confidence: 99%

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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“…Interestingly, the p ‐phenylene bridged systems 14 and 15 feature high‐spin ground states, whereas doublet ground states are determined for m ‐phenylene linked triradicals 16 and 17 . Triradicals of this type that avoid the presence of heteroatoms and of complex structural entities are obtained by introducing a σ radical center into m ‐xylylene 1 (or, alternatively, by replacing a m ‐hydrogen atom in diradicals 7–9 by a methylene group), leading to dehydro‐ m ‐xylylenes 18–20 (Chart ) …”

Section: Introductionmentioning

confidence: 99%

“…Triradicals of this type that avoid the presence of heteroatoms and of complex structural entities are obtained by introducing a s radical center into m-xylylene 1 (or, alternatively, by replacing a m-hydrogen atom in diradicals 7-9 by a methylene group), leading to dehydro-m-xylylenes 18-20 (Chart 4). [29,[66][67][68][69][70] Among the three dehydro-m-xylylene (DMX) isomers, 5-DMX 20 has received by far the most attention yet. Wenthold, Krylov, and coworkers determined the heat of formation of 20 to 141AE 5kcal/mol using mass spectrometric methods in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

EPR spectroscopic and computational characterization of the 2‐dehydro‐m‐xylylene and 4‐dehydro‐m‐xylylene triradicals

Neuhaus

Winkler

Sander

2011

J of Physical Organic Chem

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The isomeric 2‐dehydro‐ and 4‐dehydro‐1,3‐benzoquinodimethanes, 18 and 19, were generated by irradiation of the corresponding triiodo compounds in cryogenic argon matrices and characterized by electron paramagnetic resonance spectroscopy. In agreement with multireference computations, both systems possess quartet ground states, whereas in the isomeric 5‐dehydro‐m‐xylylene 20 the 2B2 doublet state lies energetically below the 4B2 state, so that no characteristic quartet signals could be observed for this triradical under similar experimental conditions. The best estimates for the adiabatic doublet–quartet energy splittings (CAS(7,7)‐AQCC/cc‐pVTZ//CAS(9,9)‐RS2c/cc‐pVTZ) of 18–20 are 10.4, 7.7, and −1.3 kcal/mol, respectively. The measured zero‐field splitting parameters of 18 and 19 are discussed in terms of the contributions of carbenoid resonance structures (spin polarization of the π‐system) to the resonance hybrid of the title triradicals. Copyright © 2011 John Wiley & Sons, Ltd.

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Reactivity and Structure of the 5-Dehydro-m-xylylene Anion

Cited by 18 publications

References 58 publications

Theory and practice of uncommon molecular electronic configurations

Theory and practice of uncommon molecular electronic configurations

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

EPR spectroscopic and computational characterization of the 2‐dehydro‐m‐xylylene and 4‐dehydro‐m‐xylylene triradicals

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