Deflected spin transmission from radical substituent to Corannulene’s curved surface: Density functional theory calculations

Fukui, Kozo; Nishida, Shinsuke; Kobayashi, Tadahiro; Sato, Kazunobu; Shiomi, Daisuke; Takui, Takeji; Nakasuji, Kazuhiro

doi:10.1016/j.poly.2005.03.069

Cited by 10 publications

(3 citation statements)

References 20 publications

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“…25 Especially in the BS singlet state (Figure 3 a), rings A, B, and C of corannulene have a large amount of spin density, and rings D and E a relatively small amount. Thus, the unbalanced spin‐delocalized nature, that is, spin‐rich (rings A–C) and spin‐poor regions (rings D and E) on the curved π‐conjugated system of corannulene, is generated in the diradical system 2 as well as in the monoradical system 1 7c,d. The origin of this unique nature is the topological effect arising from the nonalternant π conjugation of the corannulene system, which is illustrated by the canonical resonance structures 26.…”

Section: Methodsmentioning

confidence: 99%

Three‐Dimensional Intramolecular Exchange Interaction in a Curved and Nonalternant π‐Conjugated System: Corannulene with Two Phenoxyl Radicals

et al. 2010

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In recent years, curved p-conjugated molecules such as fullerenes and carbon nanotubes have attracted much attention not only in chemistry but also in materials science. [1] Their intra/intermolecular interactions within/between threedimensional (3D) curved p-electron networks play intrinsically vital roles in their unique properties and functionalities. Among them, intramolecular magnetic interaction between electronic spins on a curved p surface was extensively studied for ionic species of C 60 such as C 60 2À and C 60 3À .[2] Their electronic structures are greatly influenced by not only the dynamic spin polarization of electrons but also the negative charges on the spherical p-conjugated system and the countercation.Thus, we have focused on neutral diradical systems, which are known to be the most useful probes for studying intramolecular magnetic interactions in organic molecules. [3] While many neutral diradical derivatives relevant to planar pconjugated systems have so far been investigated, studies on curved p-conjugated neutral diradicals are limited to a single C 60 -based system in which [60]fullerene is linked to two nitroxide radicals.[4] However, their intramolecular exchange interaction J through the C 60 skeleton was very weak (j Jk À1 B j < 0.1 K)[4b] because of the small spin delocalization onto the C 60 p network from the nitroxide radicals with spin-localized nature on the NO moieties. Therefore, in order to evaluate an intramolecular exchange interaction in a curved p-conjugated system in a quantitative manner, synthesis and isolation of a stable neutral diradical derivative with extensively spindelocalized nature on its curved p-conjugated system have been the focus of current attention in molecular magnetism and open-shell chemistry. [2,5] Recently, we studied corannulene [6] -based stable neutral monoradical systems, [7] such as a phenoxyl radical derivative 1[7d] with highly spin-delocalized nature on the intrinsically 3D bowl-shaped and nonalternant p-conjugated network. These studies inspired us to propose a 3D intramolecular exchange interaction in this class of curved p radicals: in terms of geometry, they are intermediate between a planar p radical such as a phenalenyl system [8] and a tetrahedral s radical. We have now, for the first time, synthesized and isolated a corannulene-based neutral diradical, namely, 2, which has two phenoxyl radical moieties, as air-stable crystals. Due to its highly spin-delocalized nature, 2 shows strong intramolecular exchange interaction (Jk À1 B = À405 AE 2 K) through the 3D corannulene p-electron network. Bond-length analyses and DFT calculations showed that 2 has contributions from diradical canonical forms a-g and closed KekulØ structure d (Scheme 1). Furthermore, in the crystalline state the presence of three crystallographically independent diradical molecules with different curvature enabled us to study the relationship between the curvature of the corannulene p skeleton and the

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Section: Methodsmentioning

confidence: 99%

Three‐Dimensional Intramolecular Exchange Interaction in a Curved and Nonalternant π‐Conjugated System: Corannulene with Two Phenoxyl Radicals

et al. 2010

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“…DFT calculations of 1 based on the crystal structure also showed extensive spin delocalization onto the corannulene moiety from the phenoxyl moiety ( Figure 2), [15] as revealed by comparing the sum of the absolute spin density on the corannulene moiety of 1 (0.553) [16] with those of verdazyl (0.241) [17] and iminonitroxide (0.175) [17] derivatives of corannulene. This trend of the spin delocalization depending on radical moieties is attributable to the topological nature of the substituted position in the corannulene moiety, that is, the positive sign of the spin density at the carbon atom attached to the corannulene skeleton (C4 in Figure 1 and Figure 2).…”

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confidence: 99%

Curved Aromaticity of a Corannulene‐Based Neutral Radical: Crystal Structure and 3 D Unbalanced Delocalization of Spin

et al. 2008

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“…This result agrees well with works by other groups on similar systems. 34,35 We found that a π -bond is formed between atoms 20 and 21, which decreases the bond length 20-21 to 1.40Å (1.42Å in A0N). Bond 22-23 is also a π -bond type which explains its contraction by 0.14Å, compared to A0N.…”

Section: Systems Incorporating 3 N Atomsmentioning

confidence: 82%

Effects of N doping on the electronic properties of a small carbon atomic chain with distinctsp2terminations: A first-principles study

et al. 2011

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Carbon nanostructures consisting of corannulene/coronene-like pieces connected by atomic chains and doped with nitrogen atoms have been addressed by carrying out first-principles calculations within the framework of the spin-polarized density functional theory. Our results show that the conformation, charge distributions, and spin states are significantly influenced by the nitrogen incorporation in comparison to these characteristics of similar pure carbon structures. Higher concentration of incorporated nitrogen leads to a smaller highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap and different conductive states near the Fermi level. In turn the different location of the N-incorporation sites allows switching on and off of the π -electron magnetism in these systems. We found that the rotational deformation of the terminations with respect to the carbon chain depends on the number and the location of the incorporated N atoms. The most stable N-doped structures exhibit a relative rotation of the terminations of approximately 90 degrees. These findings indicate that by controllable N doping one can tune the conducting channel of carbon chains connected to sp 2 terminations; thus obtaining low band-gap nano-units.

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Deflected spin transmission from radical substituent to Corannulene’s curved surface: Density functional theory calculations

Cited by 10 publications

References 20 publications

Three‐Dimensional Intramolecular Exchange Interaction in a Curved and Nonalternant π‐Conjugated System: Corannulene with Two Phenoxyl Radicals

Three‐Dimensional Intramolecular Exchange Interaction in a Curved and Nonalternant π‐Conjugated System: Corannulene with Two Phenoxyl Radicals

Curved Aromaticity of a Corannulene‐Based Neutral Radical: Crystal Structure and 3 D Unbalanced Delocalization of Spin

Effects of N doping on the electronic properties of a small carbon atomic chain with distinctsp2terminations: A first-principles study

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