Through-Space Interactions in Non-Kekulé Biradicals

Hatanaka, Masashi; Shiba, Ryuichi

doi:10.1246/bcsj.80.1750

Cited by 11 publications

(16 citation statements)

References 20 publications

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“…In short, since simultaneous occupancy of two electrons with parallel spin in the same atomic orbital is forbidden by the Pauli principle, resultant reduction of Coulomb repulsion leads to parallel-spin preference in PNBCOs. This situation resembles that in nondisjoint biradicals 22 and one-dimensional non-Kekulé polymers, 1 in which the squared amplitudes of the PNBMO or PNBCO represent anti-parallel-spin instabilities.…”

Section: Theoreticalmentioning

confidence: 77%

“…1,22 The last expression in eq 26 makes it possible to obtain schematic representation of PNBCO by simple product between the coefficients on the same atomic site in the ð 1 ; 2 Þ-th and ð 1 þ 1; 2 Þ-th cells. approximation was applied, each PNBCO contained only ionic terms.…”

Section: Theoreticalmentioning

confidence: 99%

“…[19][20][21] Through-space interactions in nondisjoint systems also have been pointed out as another ferromagnetic interaction. 22 Similarly, possible organic ferromagnets based on non-Kekulé polymers have infinite NBMOs to form nonbonding crystal orbitals (NBCOs) which are nondisjoint. 1 Recently, ferromagnetic interactions in non-Kekulé systems have been interpreted in view of anti-parallel-spin instabilities in the product of NBMOs or NBCOs.…”

mentioning

confidence: 99%

“…1 Recently, ferromagnetic interactions in non-Kekulé systems have been interpreted in view of anti-parallel-spin instabilities in the product of NBMOs or NBCOs. 1,22 That is, triplet preference in non-Kekulé biradicals has been attributed to singlet instabilities in the product of NBMOs (PNBMO). 22 Moreover, ferromagnetic interactions in one-dimensional non-Kekulé polymers have been attributed to anti-parallel-spin instabilities in the products of NBCOs (PNBCO), 1 which is an extended concept of PNBMO.…”

mentioning

confidence: 99%

“…1 In one-dimensional non-Kekulé polymers, the former results from the squared amplitude of the same atomic site in PNBCO, and the latter results from antibonding-through-space interactions between second-nearest-neighbor carbon atomic sites in PNBCO. 1,22 However, in one-dimensional non-Kekulé polymers, defects in the polymers often destroy spin-coupling paths. 10 In order to overcome such a difficulty, two-dimensional non-Kekulé polymers with multiple spin-coupling paths have been suggested.…”

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confidence: 99%

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Ferromagnetic Interactions in Non-Kekulé Polymers. II

Hatanaka¹,

Shiba²

2008

Bulletin of the Chemical Society of Japan

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Ferromagnetic interactions in two-dimensional non-Kekulé polymers were theoretically analyzed under periodic boundary conditions. We constructed two-dimensional Wannier functions in the non-bonding crystal orbitals (NBCOs), and PNBCO (product of NBCO) were their products. Ferromagnetic interactions were attributed to anti-parallel-spin instabilities in PNBCO, similar to one-dimensional non-Kekulé polymers. The instabilities consisted of on-site terms and through-space terms. The former resulted from the squared amplitude of the same atomic site in PNBCO, and the latter resulted from antibonding-through-space interactions between second-nearest-neighbor carbon atomic sites in PNBCO.There has been increasing interest in organic ferromagnets. Mataga theoretically proposed possible organic ferromagnets based on molecular orbital methods. 2 The theory is based on topological degeneracy 3 of non-bonding molecular orbitals (NBMOs) characteristic of non-Kekulé systems. In particular, m-phenylene (1) in Figure 1 has been regarded as a robust ferromagnetic coupler in organic ferromagnets.2,3 The carbon atomic sites can be divided into two groups, that is, so-called starred atoms and unstarred atoms. 4 They can be chosen so as to be not adjacent each other. Then, the spin-quantum number of non-Kekulé systems predicted by Hund's rule becomes ðN c À 2TÞ=2, where N c and T are the number of carbon atoms and classical double bonds, respectively. 4 Ovchinnikov also proposed possible organic ferromagnets based on non-Kekulé polymers in view of valence bond theory. 5 The spin-quantum number of non-Kekulé systems predicted by Ovchinnikov is jn A À n Aþ j=2, where n A and n Aþ are identical to the number of starred and unstarred atoms, respectively. 5 This theory has been related to the spin-polarization concept in non-Kekulé systems.6 Tyutyulkov and co-workers also have designed many non-Kekulé polymers based on band theory. 7-9 A typical one-dimensional non-Kekulé polymer, poly(m-phenylene) (2), is shown in Figure 1. High-spin states of polymers and oligomers based on m-phenylene skeletons have been theoretically well established. 7,8,[10][11][12] Thus, non-Kekulé chain polymers, including poly(m-phenylene), have been promising candidates for organic ferromagnets. Recent, heteroatom-containing systems have also been investigated due to their stabilities. [13][14][15][16] Non-Kekulé chain polymers are extended systems of nonKekulé molecules. High-spin non-Kekulé molecules have ''nondisjoint'' NBMOs 17,18 which span common atoms. The ferromagnetic spin alignment in non-Kekulé systems essentially results from an exchange integral between nondisjoint NBMOs.19-21 Through-space interactions in nondisjoint systems also have been pointed out as another ferromagnetic interaction. 22 Similarly, possible organic ferromagnets based on non-Kekulé polymers have infinite NBMOs to form nonbonding crystal orbitals (NBCOs) which are nondisjoint. Recently, ferromagnetic interactions in non-Kekulé systems have been interpreted in view of anti-paral...

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Section: Theoreticalmentioning

confidence: 77%

Section: Theoreticalmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Ferromagnetic Interactions in Non-Kekulé Polymers. II

Hatanaka¹,

Shiba²

2008

Bulletin of the Chemical Society of Japan

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Dendralene auf dem Vormarsch: kreuzkonjugierte Oligoene ermöglichen den schnellen Aufbau molekularer Komplexität

Hopf

Sherburn

2012

Angewandte Chemie

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Vor 27 Jahren veröffentlichte H. Hopf den bisher einzigen umfassenden Übersichtsartikel zu verzweigten Oligoenen mit dem Titel “Dendralene – eine vernachlässigte Gruppe hochungesättigter Kohlenwasserstoffe”. Die Dendralene werden heutzutage nicht mehr vernachlässigt. Die Forschung zu Synthese, Eigenschaften und Anwendungen der Dendralene hat in jüngster Zeit viele neue Impulse erhalten, und der vorliegende Aufsatz fasst die bedeutenden Ergebnisse der letzten Jahre zusammen. Von grundlegend wichtigen Eigenschaften (der ersten Demonstration von alternierendem Verhalten seit den Annulenen) bis zu unvergleichbaren, molekulare Komplexität erzeugenden, chemischen Transformationen: Die als Dendralene bekannte Klasse der Oligoene ist erwachsen geworden! Die verschiedenen Synthesewege zu acyclischen und cyclischen Dendralenen werden analysiert und klassifiziert. Die leistungsfähigste Umwandlung der Dendralene – die Dien‐transmissive Diels‐Alder‐Reaktion (DTDA‐Reaktion) – wird in einer detaillierten Übersicht vorgestellt.

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Dendralenes Branch Out: Cross‐Conjugated Oligoenes Allow the Rapid Generation of Molecular Complexity

2012

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Twenty-seven years ago, H. Hopf published the only previous comprehensive review on branched oligoenes that had the title "Dendralenes: A Neglected Family of Hydrocarbons". The dendralenes are no longer neglected. Research into the synthesis, properties, and applications of dendralenes is rapidly gaining momentum and this Review summarizes important recent findings. From significant fundamental properties (the first demonstration of alternating behavior since the annulenes) through to unparalleled complexity-generating synthetic transformations, this fundamental oligoene family is coming of age. Effective synthetic approaches to cyclic and acyclic dendralene systems are analyzed and classified. The most powerful synthetic transformations of the dendralenes, diene-transmissive Diels-Alder reactions, are surveyed in detail.

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Through-Space Interactions in Non-Kekulé Biradicals

Cited by 11 publications

References 20 publications

Ferromagnetic Interactions in Non-Kekulé Polymers. II

Ferromagnetic Interactions in Non-Kekulé Polymers. II

Dendralene auf dem Vormarsch: kreuzkonjugierte Oligoene ermöglichen den schnellen Aufbau molekularer Komplexität

Dendralenes Branch Out: Cross‐Conjugated Oligoenes Allow the Rapid Generation of Molecular Complexity

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