Ball-, Bowl-, and Belt-Shaped Conjugated Systems and Their Complexing Abilities:  Exploration of the Concave−Convex π−π Interaction

Kawase, Takeshi; Kurata, Hiroyuki

doi:10.1021/cr0509657

Cited by 564 publications

(417 citation statements)

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“…These esthetically appealing structures have unique physical properties, and offer the possibility of creating novel supramolecular complexes. [12][13][14] The [n]CPs with five and six arene rings were synthesized in 1993, 15 whereas synthesis was attempted already in 1934 by Parekh and Guha. 16 The term nanohoops was coined by Jasti and co-workers, who in 2008 synthesized [9]CP, [12]CP, and [18]CP and studied their UV-vis spectra.…”

Section: Introductionmentioning

confidence: 99%

“…[12][13][14] The [n]CPs with five and six arene rings were synthesized in 1993, 15 whereas synthesis was attempted already in 1934 by Parekh and Guha. 16 The term nanohoops was coined by Jasti and co-workers, who in 2008 synthesized [9]CP, [12]CP, and [18]CP and studied their UV-vis spectra. 17 The selective synthesis of [12]CP has subsequently been reported in 2009 by Itami's group.…”

Section: Introductionmentioning

confidence: 99%

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Magnetically Induced Currents in [n]Cycloparaphenylenes, n = 6−11

2010

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We report calculations of the gauge-independent magnetically induced current densities in [n]cycloparaphenylenes ([n]CP), n = 6-11. In addition to the neutral [n]CPs, the dianion of [6]CP and the current densities of the corresponding metal complexes Li 2 [6]CP and Mg[6]CP are also investigated. By the ring current criterion, the [6]CP with 4n π electrons has a slight antiaromatic character, while [7]CP has (4n þ 2) π electrons and is weakly aromatic with a ring current susceptibility strength that is about 25% of the ring current of benzene. The larger neutral [n]CPs, n = 8-11, do not sustain any net ring current around the nanohoop and are essentially nonaromatic. The weak paramagnetic ring current susceptibility of [6]CP flows along a 4n π pathway on either edge of the phenylene rings. For the dianions, the ring current susceptibility strengths are 24-35 nA/T diatropic and thus the addition of two electrons induces an electron delocalization and an aromatic character of the nanohoops. The dilithium complex of [6]CP with (4n þ 2) π electrons is aromatic with a net ring current strength of 28 nA/T or 2.4 times the ring current strength of benzene, involving all 62 π electrons in the current pathway. The 1 H NMR chemical shieldings and the nucleus-independent chemical shifts correlate with the strengths of the magnetically induced currents. The aromatic [n]cycloparaphenylenes have a quinoid structure, whereas the weakly aromatic or nonaromatic ones are benzoidic.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetically Induced Currents in [n]Cycloparaphenylenes, n = 6−11

2010

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“…2,5,10 In addition, the cavity of CPPs offers a unique opportunity in supramolecular chemistry to study concave convex ³³ interactions and fabricate hierarchically ordered ³ materials. 11,12 Despite their simple structure, however, the synthesis of CPPs was only recently achieved by three groups including our own despite intensive efforts that spanned more than half a century.…”

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confidence: 99%

Selective Synthesis of [6]-, [8]-, and [10]Cycloparaphenylenes

et al. 2013

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The selective synthesis of [6]-, [8]-, and [10]cycloparaphenylenes (CPPs) was achieved by a new synthetic route involving Ni(0)-mediated coupling of bis(para-haloaryl)dinuclear arylplatinum complexes and the reductive elimination of the complexes. Importantly, the highly strained [6]CPP was prepared in good overall yield.Cycloparaphenylenes (CPPs; Figure 1a), being hoop-shaped ³-conjugated molecules consisting of para-linked phenylene rings, have recently gained much attention from a variety of disciplines, which, besides their structural beauty, is mostly associated with the topologically unique array of ³-orbitals. 15Since CPPs are the smallest structural units of armchair carbon nanotubes (CNTs; Figure 1b), their application in electronic and optoelectronic devices 69 and their use as a seed compound for the synthesis of structurally uniform CNTs have been suggested. 2,5,10 In addition, the cavity of CPPs offers a unique opportunity in supramolecular chemistry to study concave convex ³³ interactions and fabricate hierarchically ordered ³ materials.11,12 Despite their simple structure, however, the synthesis of CPPs was only recently achieved by three groups including our own despite intensive efforts that spanned more than half a century.Bertozzi and Jasti were the first to synthesize [9]-, [12]-, and [18]CPPs utilizing cis-cyclohexa-2,5-diene-1,4-diyl as the key precursor (Scheme 1a). 13 The subsequent extension of this synthetic strategy by Jasti realized the selective synthesis of a series of [6] 12 Isobe applied our method to the synthesis of the shortest sidewall segments of helical CNTs. 32,33 Very recently, we reported the selective synthesis of [10]CPP through an Lshaped cis-substituted bis(para-haloaryl)platinum complex. 34Theoretical studies by our group have suggested that, 31 in sharp contrast to linear oligoparaphenylenes, the gap between the highest-occupied and lowest-unoccupied molecular orbital (HOMOLUMO gap) of CPPs becomes narrower as the number of phenylene rings decreases, which is due to increasing and decreasing HOMO and LUMO energies, respectively. As a result, compared to larger CPPs, CPPs of small ring size should display a range of intriguing properties, including a higher redox activity. Unfortunately, despite recent developments, the synthesis of small CPPs still poses serious synthetic difficulties; the

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“…[16] Recent theoretical and experimental studies on fullerene complexes predicted that the strong host-guest interactions are largely the result of dispersion force and are enhanced by weak electrostatic interactions. [17,18] A number of studies proposed that the electrostatic difference between 5:6 and 6:6 ring fusions play an important role in the electrostatic interaction. [19] Herein we have shown, however, that the K a value of 4'1 is almost comparable to that of 2'C 60 .…”

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confidence: 99%