5‐Dehydro‐1,3‐quinodimethane: A Hydrocarbon with an Open‐Shell Doublet Ground State

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

doi:10.1002/ange.200352990

Cited by 4 publications

(4 citation statements)

References 27 publications

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“…23 Similarly, 5-dehydro-1,3quinodimethane (DMX) is a triradical with an openshell 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. 41,42 The dominant product of electron attachment to DMX is a rare triplet carbanion. 43 Topologically different isomers of DMX II and III with nondisjoint NBMOs have high-spin (quartet) ground states ( Figure 3).…”

Section: Prototypical Casesmentioning

confidence: 99%

Theory and practice of uncommon molecular electronic configurations

Gryn’ova

Coote

Corminbœuf

2015

WIREs Comput Mol Sci

102

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: Prototypical Casesmentioning

confidence: 99%

Theory and practice of uncommon molecular electronic configurations

Gryn’ova

Coote

Corminbœuf

2015

WIREs Comput Mol Sci

102

112

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“…Yet, there is growing theoretical and experimental evidence for its violation in quantum dots 2 , transition metal complexes 3,4 and even fully organic molecules 5 . Moreover, a limited number of recent publications report non-aufbau occupation of molecular orbitals in open-shell molecules (i.e., radicals), where the molecular orbital accommodating the unpaired electron (the singly-occupied molecular orbital, or SOMO) is no longer energetically the highest occupied one (HOMO).…”

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confidence: 99%

Switching radical stability by pH-induced orbital conversion

et al. 2013

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In most radicals the singly occupied molecular orbital (SOMO) is the highest-energy occupied molecular orbital (HOMO); however, in a small number of reported compounds this is not the case. In the present work we expand significantly the scope of this phenomenon, known as SOMO-HOMO energy-level conversion, by showing that it occurs in virtually any distonic radical anion that contains a sufficiently stabilized radical (aminoxyl, peroxyl, aminyl) non-π-conjugated with a negative charge (carboxylate, phosphate, sulfate). Moreover, regular orbital order is restored on protonation of the anionic fragment, and hence the orbital configuration can be switched by pH. Most importantly, our theoretical and experimental results reveal a dramatically higher radical stability and proton acidity of such distonic radical anions. Changing radical stability by 3-4 orders of magnitude using pH-induced orbital conversion opens a variety of attractive industrial applications, including pH-switchable nitroxide-mediated polymerization, and it might be exploited in nature. AbstractIn most radicals the singly-occupied molecular orbital (SOMO) is the highest-energy occupied one

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“…In addition, reaction of fluoride with disilanes causes cleavage of SiOSi bonds to produce silyl anions [15,16]. Lastly, a variation of fluoride-induced desilylation involving the reaction of trimethylsilyl substituted anions has also been used to prepare open-shell anions of biradicals, triradicals, and beyond [9,[17][18][19][20][21][22].…”

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confidence: 99%

Fluorotrimethylsilane affinities of anionic nucleophiles: A study of fluoride-induced desilylation

Krouse

Wenthold

2005

J. Am. Soc. Mass Spectrom.

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In this study, preparation and decomposition of five novel pentavalent fluorosiliconates, RSi(CH 3 ) 3 F Ϫ (R ϭ CH 3 CH 2 O, CF 3 CH 2 O, (CH 3 ) 2 CHO, (CH 3 ) 3 SiO, and (CH 3 ) 3 SiNH) is used to investigate the process of fluoride-induced desilylation. The siliconates were characterized by collision-induced dissociation and energy-resolved mass spectrometry. Decomposition of RSi(CH 3 ) 3 F Ϫ leads to loss of the nucleophile R Ϫ and FSi(CH 3 ) 3 , except in the case of (CH 3 ) 3 SiNHSi(CH 3 ) 3 F Ϫ , where HF loss is also observed. Ion affinities for FSi(CH 3 ) 3 have been measured for all five nucleophiles, and compare well with computational predictions. The observed trend of the bond dissociation energies resembles the trend of ⌬H acid values for the corresponding conjugate acids, RH. Additionally, this data has been incorporated with existing thermochemistry to derive fluoride affinities for four of the silanes (R ϭ CH 3 CH 2 O, (CH 3 ) 2 CHO, (CH 3 ) 3 SiO, and (CH 3 ) 3 SiNH). We use the fluoride affinity of the silanes and the FSi(CH 3 ) 3 affinity of the departing nucleophilic anion to assess the feasibility of fluorideinduced desilylation of the silanes examined in this work. (J Am Soc Mass Spectrom 2005, 16, 697-707)

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5‐Dehydro‐1,3‐quinodimethane: A Hydrocarbon with an Open‐Shell Doublet Ground State

Cited by 4 publications

References 27 publications

Theory and practice of uncommon molecular electronic configurations

Theory and practice of uncommon molecular electronic configurations

Switching radical stability by pH-induced orbital conversion

Fluorotrimethylsilane affinities of anionic nucleophiles: A study of fluoride-induced desilylation

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