Synthesis and molecular structure of [7]circulene

Yamamoto, Kōji; Harada, Tadao; Okamoto, Yoshio; Chikamatsu, Hiroaki; Nakazaki, Masao; Kai, Yasushi; NAKAO, T.; Tanaka, Mitsuya; Harada, Shigeharu; Kasai, Nobutami

doi:10.1021/ja00219a036

Cited by 196 publications

(103 citation statements)

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“…A nearby saddle-shaped structure of C 2 symmetry, 3b, lies ca. 35 kJ mol À1 [14] lower in energy and compares closely with the experimental structure obtained from low-temperature X-ray measurements [8], although the precise position of the minimum is difficult to establish because of the extremely low energy of the corrugating modes [14]. The geometry of 3 was optimised at the RHF/ 6-31G** level under the constraints of D 7h and C 2 symmetry, respectively, using GAMESS-UK [17].…”

Section: Structure Of [7]circulene 3a-bmentioning

confidence: 79%

“…In Table 2 the computed CTOCD-PZ2 [19,20] 13 C ðd C Þ and 1 H ðd H Þ NMR chemical shifts for planar 3a and saddle-shaped 3b are presented and compared with available experimental values [8,13]. In agreement with the shallow corrugation potential for 3b ( [14] and see Section 2) and the observation that 3b in solution possesses a timeaveraged planar D 7h structure, even at À90°C, a better fit between theory and experiment is obtained using the symmetry-averaged d C values rather than those computed for the D 7h struc- Fig.…”

Section: Global and Local Magnetic Properties Of 3a And 3bmentioning

confidence: 99%

“…In this Letter we report new current density maps and integrated magnetic properties for [7]circulene (3) [8], a compound which differs from its homologues 1 and 2 by its complex dynamics. Whilst 2 has a D 6h structure both in solution and in the solid state [9], 1 is bowl-shaped in the solid state [10] but has a time-averaged planar D 5h structure in solution (as established by temperature-dependent 1 H NMR) due to rapid bowl-to-bowl interconversion [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Whilst 2 has a D 6h structure both in solution and in the solid state [9], 1 is bowl-shaped in the solid state [10] but has a time-averaged planar D 5h structure in solution (as established by temperature-dependent 1 H NMR) due to rapid bowl-to-bowl interconversion [11,12]. In contrast, 3 has a saddle-shaped structure of C 2 symmetry (3b) in the solid state [8] and a time-averaged planar structure of D 7h symmetry (3a) in solution (with one 1 H and three 13 C NMR resonances), which is not frozen out even at À90°C [13] (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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A simple model for counter-rotating ring currents in [n]circulenes

Acocella

Havenith

Steiner

et al. 2002

Chemical Physics Letters

100

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Ab initio current density maps for [7]circulene computed using the ipsocentric CTOCD-DZ/6-31G**//RHF/6-31G** method show that in both planar [3a (D 7h Þ] and non-planar, saddle-shaped [3b (C 2 Þ] geometries this molecule sustains similar counter-rotating rim (diatropic) and hub (strongly paratropic) currents. A survey of the orbital contributions to the current density reveals that 3 like corannulene (1) is a 4d + 4p system with just eight magnetically active and 20 magnetically inactive p electrons. The graph-theoretical H€ u uckel-London model describes the ring-current patterns of [n]circulenes in terms of a coupling strength (the ratio of radial and tangential resonance integrals) that charts the variation from the decoupled con-rotating currents of the [n]annulene-within-an-[m]annulene model to the fully coupled counter-rotating currents of the real [n]circulene. Ó

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Section: Structure Of [7]circulene 3a-bmentioning

confidence: 79%

Section: Global and Local Magnetic Properties Of 3a And 3bmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A simple model for counter-rotating ring currents in [n]circulenes

Acocella

Havenith

Steiner

et al. 2002

Chemical Physics Letters

100

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“…The bromination of compound 96 under standard bromination conditions [25][290] [306] afforded the product 97 in 38% yield, while 45% of the over brominated product was also isolated. The biphenyl 96 was therefore only treated with NBS (without radical starter) in carbon tetrachloride under an inert argon atmosphere.…”

Section: The Variable Biphenyl Intermediatesmentioning

confidence: 99%

Shape‐Switchable Azo‐Macrocycles

et al. 2009

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The synthesis of four shape‐switchable macrocycles comprising different peripheral substituents is described. The macrocycles 1–4 consist of m‐terphenyl semicircles interlinked by two azo joints. These macrocycles were assembled from nitro‐functionalized m‐terphenyl moieties through reductive dimerization. The semicircles were assembled through Suzuki cross‐coupling reactions. The molecular weights of the macrocycles were determined by vapour pressure osmometry, because mass spectrometry failed in the cases of 2 and 3. The E → Z photoisomerization reactions were analysed by UV/Vis spectroscopy complemented by 1H NMR studies. A very slow thermal back‐reaction indicated considerable stabilization of the Z isomer. The reduced efficiency of the thermal back‐reaction probably arises from the reduced degree of freedom due to the mechanical interlinking of the two azo groups. The photostationary state consisted of all‐Z (85 %) and all‐E isomers (15 %). The E → Z transformation induced by irradiation displayed simple exponential kinetics, which indicates pairwise switching of the two azo groups in a macrocycle, at least on the timescale under investigation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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