Ring Currents in a Proposed System Containing Planar Hexacoordinate Carbon, CB62−

Havenith, Remco W. A.; Fowler, Patrick W.; Steiner, Erich

doi:10.1002/1521-3765(20020301)8:5<1068::aid-chem1068>3.0.co;2-z

Cited by 47 publications

(57 citation statements)

References 12 publications

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“…[12][13][14]16,17,[26][27][28]43,[45][46][47][48] Further, the calculation of highly anionic species often results in technical problems as convergence failures. Therefore, we studied closed-shell clusters with an increasing number of Li + counterions, starting from Al 4 2-, Al 4 Li -, Al 4 Li 2 , Al 4 Li 3 -, and Al 4 Li 4 .…”

Section: Resultsmentioning

confidence: 99%

Structure and Electron Delocalization in Al₄^2- and Al₄^4-

Islas

Heine

Merino

2007

J. Chem. Theory Comput.

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Structure, dynamics, and electron delocalization of Al4(2-) and Al4(4-) based clusters are investigated. Gradient-corrected Density-Functional Born-Oppenheimer Molecular Dynamics simulations indicate that Al4(2-) based clusters have a rigid planar Al framework, while the Al4(4-) based moieties show large distortions from planarity. The induced magnetic field analysis of these species indicates that both systems have diatropic σ-systems, while the π-system is diatropic for Al4(2-) and paratropic for Al4(4-). The total magnetic response is diatropic for Al4(2-), while Al4(4-) is "bitropic": it has typical antiaromatic long-range cones, while the magnetic field in the Al4(4-) ring plane is similar to that of aromatic annulenes.

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Section: Resultsmentioning

confidence: 99%

Structure and Electron Delocalization in Al₄^2- and Al₄^4-

Islas

Heine

Merino

2007

J. Chem. Theory Comput.

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“…Notably, a series of hypercoordinate planar carbon species with boron ligands have been proposed 13–15. 16a,c,e Although none of these species is the global minimum on the potential‐energy surfaces, it has been suggested that they may be viable experimentally.…”

Section: Comparison Of the Experimental Vdes Of Cb7− To The Calculatementioning

confidence: 99%

“…16a,c,e Although none of these species is the global minimum on the potential‐energy surfaces, it has been suggested that they may be viable experimentally. The two proposed hexa‐ and heptacoordinate carbon species are D 6 h CB 6 2− 13a,b,d, 14c, 15 and D 7 h CB 7 − ,13b, 14c respectively. The CB 7 − species is isoelectronic to B 8 2− , which we have shown previously to have a global‐minimum D 7 h structure with a heptacoordinate boron atom 17–20.…”

Section: Comparison Of the Experimental Vdes Of Cb7− To The Calculatementioning

confidence: 99%

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

et al. 2007

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In organic chemistry, saturated carbon is known to bond to four ligands tetrahedrally, as first recognized independently by J. H. vant Hoff and J. A. Le Bel in 1874. However, after the proposal by Hoffmann and co-workers of tetracoordinate planar carbon in 1970, [1] extensive experimental and theoretical efforts were made to search for so-called anti-vant Hoff/ anti-Le Bel molecules (for recent reviews, see references [2][3][4]). In particular, the first experimental and theoretical realization of pentaatomic planar-coordinated carbon species in 1999 and 2000, [5][6][7][8] which confirmed earlier theoretical predictions, [9,10] has stimulated renewed interest in designing new tetracoordinate [11,12] and even hypercoordinate planar carbon molecules. [13][14][15][16] Notably, a series of hypercoordinate planar carbon species with boron ligands have been proposed. [13-15, 16a,c,e] Although none of these species is the global minimum on the potentialenergy surfaces, it has been suggested that they may be viable experimentally. The two proposed hexa-and heptacoordinate carbon species are D 6h CB 6 2À [13a,b,d, 14c, 15] and D 7h CB 7 À , [13b, 14c] respectively. The CB 7 À species is isoelectronic to B 8 2À , which we have shown previously to have a global-minimum D 7h structure with a heptacoordinate boron atom. [17][18][19][20] The D 7h CB 7 À can be viewed as replacing the central B À ion in B 82À by a C atom. Herein we report serendipitous experimental observation of CB 7 À . It was investigated by photoelectron spectroscopy (PES) and ab initio calculations, which showed that the observed species is a C 2v CB 7 À ion in which the C atom replaces a B À ion at the rim of the D 7h B 8 2À molecular wheel.The experiment was performed with a laser-vaporization cluster source and a magnetic-bottle photoelectron spectrometer (see Experimental Section).[21] We recently modified our cluster source by adding a 10-cm-long and 0.3-cm-diameter stainless steel tube to enhance cluster cooling.[22] We were using boron clusters, which we have previously investigated extensively, [17][18][19][20][23][24][25][26][27][28] to test the new cluster-source conditions. A 10 B-enriched disk target containing a small amount of Au was used as the laser-vaporization target.[23] Under certain conditions, when the vaporization laser was not perfectly aligned, we noted that in addition to the pure boron clusters we were also able to produce clusters containing one or two carbon atoms, as shown in Figure 1. The carbon most likely originated from impingement of the slightly misaligned vaporization laser beam on the stainless steel tubing. The trace amount of carbon contamination was ideal to produce boron clusters doped with only one or two carbon atoms, and the beam condition was stable and reproducible.The peak of the CB 7 À cluster is particularly intense with abundance as strong as those of the nearby pure B x À clusters (Figure 1). Its photoelectron spectra at two detachment laser wavelengths are shown in Figure 2. The 193-nm spectrum rev...

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“…CB 6 2− ist das erste Beispiel eines aromatischen Moleküls mit sechs π‐Elektronen und einem zentralen hexakoordinierten Atom. Seine Aromatizität wurde durch stark negative NICS‐Werte über dem Ring und den diamagnetischen π‐Ringstrom, der vom Zentralatom ungestört im Molekül kreist, bestätigt 73…”

Section: Planar Hexa‐ Und Höher Koordinierter Kohlenstoffunclassified

Vier Jahrzehnte Chemie der planar hyperkoordinierten Verbindungen

et al. 2015

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Planar vierfach koordinierter Kohlenstoff (ptC) wurde seit 1874 für über ein Jahrhundert als unplausibel angesehen. Danach konnten jedoch Beispiele rechnerisch vorhergesagt und experimentell realisiert werden. Sowohl elektronische als auch mechanische Effekte (z. B. in kleinen Ringen und Käfigen) stabilisieren diese ungewöhnlichen Bindungsanordnungen. Konzepte basierend auf den Bindungsmotiven des planaren Methans/planaren Methandikations können erweitert werden, um planar hyperkoordinierte Strukturen anderer chemischer Elemente zu entwerfen. Zahlreiche Konfigurationen von verschiedenen Zentralatomen (Haupt‐ und Übergangsmetallelementen) in einer Ebene mit Koordinationszahlen von bis zu zehn werden diskutiert. Die Evolution von solchen planaren Konfigurationen aus kleinen Molekülen zu Clustern, nanoskopischen Spezies bis hin zu Festkörpern wird aufgezeigt. Für einige experimentell hergestellte planare Materialien wurden außergewöhnliche elektrische und magnetische Eigenschaften nachgewiesen.

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Ring Currents in a Proposed System Containing Planar Hexacoordinate Carbon, CB62−

Cited by 47 publications

References 12 publications

Structure and Electron Delocalization in Al₄^2- and Al₄^4-

Structure and Electron Delocalization in Al₄^2- and Al₄^4-

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

Vier Jahrzehnte Chemie der planar hyperkoordinierten Verbindungen

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Ring Currents in a Proposed System Containing Planar Hexacoordinate Carbon, CB62−

Cited by 47 publications

References 12 publications

Structure and Electron Delocalization in Al42- and Al44-

Structure and Electron Delocalization in Al42- and Al44-

CB7−: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

Vier Jahrzehnte Chemie der planar hyperkoordinierten Verbindungen

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Structure and Electron Delocalization in Al₄^2- and Al₄^4-

Structure and Electron Delocalization in Al₄^2- and Al₄^4-

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon