Dianions and dications derived from bridged [4n + 2]annulenes. Paratropism as a function of ring size, conformation, and configuration

Muellen, K.; Meul, T.; Schade, P.; Schmickler, Hans; Vogel, Emanuel

doi:10.1021/ja00250a038

Cited by 37 publications

(21 citation statements)

References 5 publications

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“…The 1 H NMR resonances of crown ether in 4 and 5 lie in the range of 9.2–6.2 ppm, depending on the concentration used. The paramagnetic shielding in 2 and 3 and paratropic ring current1a, 26 in 4 and 5 make the interpretation of the NMR spectra quite challenging. Our speculation is that the abovementioned dependence of the δ H chemical shifts on concentrations and temperatures may have resulted from various types of metal ion or crown ether binding to corannulene anions existing in solutions.…”

Section: Resultsmentioning

confidence: 99%

How Charging Corannulene with One and Two Electrons Affects Its Geometry and Aggregation with Sodium and Potassium Cations

Zabula

Spisak

Filatov

et al. 2012

Chemistry A European J

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Bowl-shaped mono- and dianions are prepared by reduction of corannulene (C(20)H(10), 1) with sodium and potassium metals in the presence of [18]crown-6 ether. Single-crystal X-ray diffraction studies of two sodium salts, [Na(THF)(2)([18]crown-6)](+)[1(-)] (2a) and [Na([18]crown-6)](+)[1(-)] (2b), reveal the presence of naked corannulene monoanions 1(-) in both cases. In contrast, the potassium adduct, [K([18]crown-6)](+)[1(-)] (3), shows an η(2)-binding of the K(+) ion to the convex face of 1(-). For the first time, corannulene dianions have been isolated as salts with sodium, [Na(2)([18]crown-6)](2+)[1(2-)] (4a) and [Na(THF)(2)([18]crown-6)](+)[Na([18]crown-6)](+)[1(2-)] (4b), and potassium counterions, [K([18]crown-6)](2)(+)[1(2-)] (5). Their structural characterization reveals geometry perturbations upon addition of two electrons to a bowl-shaped polyarene. It also demonstrates η(5)- or η(6)-binding of metals to the curved carbon surface of 1(2-), depending on the crystallization conditions. Both mono- and doubly-charged corannulene bowls show the preferential exo binding of Na(+) and K(+) ions in all investigated compounds. Various types of C-H···π interactions are found in the crystals of 2-5. The UV/Vis, ESR, and (1)H NMR spectroscopic studies of 2-5 indicate different coordination environment of corannulene anions in solution, depending on the metal ion.

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Section: Resultsmentioning

confidence: 99%

How Charging Corannulene with One and Two Electrons Affects Its Geometry and Aggregation with Sodium and Potassium Cations

Zabula

Spisak

Filatov

et al. 2012

Chemistry A European J

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“…[8] However, a Jahn-Teller distortion led to the eventual detection of 1 H-and 13 C-NMR spectra of the dianion. [30] The extreme high-field shifts of the protons (δ ϭ -5.6) are typical of molecules with a paratropic ring current [31] and can be explained by the ''annulene model'', where a cyclopentadienyl anion (6e/5C) is placed in the center of an antiaromatic (16e/15C) annulene perimeter.…”

Section: Corannulene: a Representative Of Curved π-Systemsmentioning

confidence: 99%

π-Conjugated Anions: From Carbon-Rich Anions to Charged Carbon Allotropes

Benshafrut

Shabtai

Rabinovitz³

et al. 2000

Eur. J. Org. Chem.

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“…Mdlen and coworkers reported the synthesis and properties of trans-I5,16- [33] and of syn-I ,6:8,13-diimino[l4]annnlene [34]. Mullen and coworkers, by the same method, studied the kinetics of the reduction of a homologous series of Nukuguwu-type annulenes [35] and various dianions and dications derived from bridged [ 14]annulenes [36].…”

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confidence: 99%