Visualisation of counter-rotating ring currents in kekulene

Steiner, Erich; Fowler, Patrick W.; Jenneskens, Leonardus W.; Acocella, Angela

doi:10.1039/b009763m

Cited by 71 publications

(89 citation statements)

References 15 publications

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“…Previous ab initio calculations at the RHF level using various basis sets on both 3a (D 7h Þ and 3b (C 2 Þ have indicated that 3 is a floppy molecule with a notoriously shallow corrugation potential [14] (see also [15]). We show here that [7]circulene (3), despite its floppiness, sustains the same global pattern of counter-rotating currents as corannulene (1) and coronene (2), and we provide a graph-theoretical model that accounts for this behaviour of [n]circulenes in general (see also [16]). The simple model gives a one-parameter continuum of descriptions from the [n]annulenewithin-an- [m]annulene to the strongly coupled [n]circulenes.…”

Section: Introductionmentioning

confidence: 62%

“…The similarity of the ab initio current density maps of [n]circulenes for n ¼ 5 (1), 6 (2) [6], 7, and 18 (kekulene, [16]), is rationalised by a simple, purely graph-theoretical model, based on H€ u uckelLondon theory. The general pattern of circulation in an [n]circulene is described by a one-parameter model that gives a continuum description from the fully decoupled con-rotating currents of the [n]annulene-within-an- [m]annulene to the more physically realistic fully coupled counter-rotating currents of the real [n]circulene.…”

Section: Discussionmentioning

confidence: 95%

“…The advantages of the CTOCD-DZ method for current density and the CTOCD-PZ2 (paramagnetic zero) variant for integrated magnetic properties have been well rehearsed in the literature [6,16,19,20]. For planar 3a the r-, p-and total (r + pÞ current densities induced by a unit magnetic field acting along the principal axis are plotted in a plane 1 a 0 above that of the central ring (that is, close to the maximum p density and where current flow is effectively parallel to the molecular plane [21]).…”

Section: Magnetic Propertiesmentioning

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: Introductionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 95%

Section: Magnetic Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

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

Acocella

Havenith

Steiner

et al. 2002

Chemical Physics Letters

100

View full text Add to dashboard Cite

show abstract

“…(The only circumstances in recent work where a different assumption about ring areas needs to be made are in the case of structures with 'holes', such as kekulene [6,22,[30][31][32][33] and the p-coronenes. [13,14] ) Lillington et al [1] have pointed out that 1 is indeed planar (with C4h symmetry) and so also is 2, in a transitional form (with D4h symmetry); in reality, however, 2 is bowlshaped in its equilibrium conformation, with symmetry C4v.…”

Section: Calculationsmentioning

confidence: 99%

Comparisons of π-Electron Ring-Current and Bond-Current Patterns Calculated by Topological (‘HLPM’) and Ab Initio (‘Ipso-Centric’) Formalisms for Two Isomeric Conjugated Hydrocarbons, Corazulene and Cornaphthalene

Dickens¹,

Mallion²

2015

Croat. Chem. Acta

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Abstract:The π-electron ring-currents and bond-currents associated with the isomeric structures corazulene (1) and cornaphthalene (2) are calculated by means of the rudimentary topological Hückel-London-Pople-McWeeny (HLPM) method (which is entirely equivalent to the recently named 'graph-theoretical CD-HL' approach).These currents are compared with analogous quantities computed by Lillington et al. by use of the more-sophisticated ipso-centric ab initio approach. The simple HLPM method is seen to exhibit a remarkable ability to reproduce complex patterns of current in large polycyclic hydrocarbons -the successful prediction of which, ostensibly, might naïvely be expected to be the preserve only of more sophisticated, and much less intuitive, ab initio calculations. This conclusion is entirely consistent with findings from contemporary work on other structures by the present, and other, authors.

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“…Also the Clar structures of circumcoronene (32) and kekulene (33) are supported by BV(ELF π )s and ΔBV(ELF π )s as the A and D (32) and A (33) hexagons host -sextets. Kekulene, synthesized by Staab and Diederich in 1978 [81], was earlier suggested to be a benzenoid rather than a superaromatic annulenoid hydrocarbon according to graph theory, NICS, and current-density map calculations [82][83][84]. From the ELF  results one can note that both the inner [18]annulene and the outer [30]annulene paths have large variations in BV(ELF  ) suggesting poor overall -delocalization along these circuits.…”

Section: Polybenzenoids 31-34mentioning

confidence: 99%

On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the π-Contribution to the Electron Localization Function

et al. 2010

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Abstract:The degree of -electron (de)localization and aromaticity of a series of polybenzenoid hydrocarbons (PBHs) has been analyzed through the π-contribution to the electron localization function (ELF π ), calculated at the B3LYP/6-311G(d,p) hybrid density functional theory level. The extent of -electron delocalization in the various hexagons of a PBH was determined through analysis of the bifurcation values of the ELF  basins (BV(ELF  )), the spans in the bifurcation values in each hexagon (ΔBV(ELF π )), and the ring-closure bifurcation values of the ELF π (RCBV(ELF π )). These computed results were compared to the qualitative description of local aromaticities of the different hexagons in terms of Clar structures with -sextets. Benzene, [18]annulene, and thirty two PBHs were analyzed at their equilibrium geometries, and benzene and triphenylene were also analyzed at bond length distorted structures. In general, the description of PBHs in terms of Clar valence structures is supported by the ELF  properties, although there are exceptions. For PBHs at their equilibrium geometries there is a clear sigmoidal relationship between the CC bond lengths and the amount of -electron (de)localization at these bonds, however, this relationship is lost for bond distorted geometries. In the latter cases, we specifically examined benzene in D 3h symmetric "1,3,5-cyclohexatriene" structures and triphenylene in eight different structures. From the distorted benzenes and triphenylenes it becomes clear OPEN ACCESSSymmetry 2010, 2 1654 that there is a distinct tendency for the -electron network to retain delocalization (aromaticity). The ELF  analysis thus reveals an antidistortive rather than a distortive behavior of the -electrons in these investigated compounds.

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Visualisation of counter-rotating ring currents in kekulene

Cited by 71 publications

References 15 publications

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

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

Comparisons of π-Electron Ring-Current and Bond-Current Patterns Calculated by Topological (‘HLPM’) and Ab Initio (‘Ipso-Centric’) Formalisms for Two Isomeric Conjugated Hydrocarbons, Corazulene and Cornaphthalene

On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the π-Contribution to the Electron Localization Function

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