A study of the synthesis and properties of [26](1,2,3,4,5,6)cyclophane (superphane)

Sekine, Yasuo; Boekelheide, V.

doi:10.1021/ja00397a032

Cited by 84 publications

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“…69 At the latter pressure, graphite begins to undergo a phase transition: carbon-carbon single bonds begin to form between its planes. 71 the two rings are reported to eclipse perfectly (see Figure 9b). 70 For comparison, the interplanar spacing in graphite is both much longer, 3.354 Å, and less confrontational: the layers do not eclipse.…”

Section: Additional Discussion Of [C 3 H 3 O 3 ] 2 2+mentioning

confidence: 93%

Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Kim¹,

Thi²,

Heo³

et al. 2008

J. Phys. Chem. C

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A single crystal of Ag 12 -A (zeolite LTA) was prepared by the dynamic ion-exchange of Na 12 -A with aqueous 0.05 M AgNO 3 . It was washed with CH 3 OH and allowed to react with a stream of 0.05 M KCl in CH 3 OH at 294 K. The crystal structure of the product |K 2.35 Ag 1.1 (Ag 4 Cl 4 ) 0.45 (C 3 H 3 O 3 ) 1.1 (K 3 Cl) 3.45 (K 3 (OH) 2 ) 0.55 (H 2 O) g3.0 |-[Si 12 Al 12 O 48 ]-LTA (a ) 12.292(1) Å) was determined by single-crystal X-ray diffraction in the cubic space group Pm3 j m at 294 K. It was refined to the final error index, R 1 ) 0.052, based on the 371 reflections for which F o > 4σ(F o ). Ag 4 Cl 4 nanoclusters were found in about 45% of the sodalite cavities. Each Ag 4 Cl 4 cluster (interpenetrating tetrahedra; symmetry T d , Ag-Cl ) 3.105(17) Å) is held in place by the coordination of each of its four Ag + ions to three oxygens of the zeolite framework (Ag-O ) 2.493(5) Å) and by the coordination of each of its four Cl -ions to a K + ion through a 6-ring (Cl-K ) 2.70(3) Å). In each of the remaining 55% of the sodalite cavities, two reduced planar 1,3,5-tripyrylium cations, [(CH) 3 O 3 ] 2 2+ (C-O ) 1.52(3) Å), are found. These parallel eclipsed rings (symmetry D 3d ) have an interplanar distance of only 2.43 Å due to σ double bonding between the rings, the result of four electrons in 12-center bonding π* orbitals, and to polar attraction. Each ring makes three strong hydrogen bonds (CH · · · O ) 2.84(3) Å) to oxygens of the zeolite framework, and a Ag + ion coordinates to the three oxygens of one ring (Ag-O ) 2.68(9) Å). The large cavities are filled with K + , Cl -, Ag + , OH -, and H 2 O; the K 3 Cl 2+ unit predominates. The 1,3,5-tripyrylium ring, isoelectronic with benzene, had not been reported before.

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Section: Additional Discussion Of [C 3 H 3 O 3 ] 2 2+mentioning

confidence: 93%

Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Kim¹,

Thi²,

Heo³

et al. 2008

J. Phys. Chem. C

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“…In all compounds susceptibilities at the C on the rings are much lower than those of the carbon atoms on the side chains. This is due to different hybridization, carbon atoms on the rings have an sp 2 hybridization while carbon atoms on the side chain are sp 3 . This is also indicative of electron delocalization.…”

Section: Magnetic Propertiesmentioning

confidence: 99%

“…It is highly symmetrical, D 6h , and the rings are in a eclipsed conformation, with the planar regular benzene rings separated by 2.624 Å. Photoelectron spectroscopy of this compound has also been reported [3,5]. It was shown that throughspace and through-bond interactions are important to understand the splitting of the benzene molecular orbitals (MOs); the first ionization energy of 7.55 eV is a low value for the [2 n ] cyclophanes.…”

Section: Introductionmentioning

confidence: 97%

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Theoretical description of aromaticity in superphane cages

Mireles

Salcedo

Sansores

et al. 2000

Int. J. Quantum Chem.

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“…Clearly, gas-phase dimerization is the method of choice for converting benzocyclobutenes to dibenzocyclooctadienes. Thus, for example, 4,5-dimethylbenzocyclobutene 12 is readily converted by nitrogen-flow gas-phase pyrolysis at 400'C to 13 in 63% yield (14). (15), identical in all respects with an authentic sample (15) in 10% yield.…”

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confidence: 99%

Gas-phase pyrolytic formation and dimerization of benzocyclobutenes: Synthesis of [2 ₄ ](1,2,4,5) cyclophane

Eaton¹,

Laganis²,

Boekelheide³

1981

Proc. Natl. Acad. Sci. U.S.A.

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Gas-phase pyrolysis of benzocyclobutenes in a nitrogen stream at 450(C is a convenient efficient method for preparing dibenzocyclooctadienes. Application of this method to benzo [1,2;4,5]dicyclobutene gives [24](1,2,4,5)cyclophanedirectly.However, under the same reaction conditions, 3,6-dimethylbenzo- [1,2;4,5]dicyclobutene gives the open [2.2]orthocyclophane derivative, whose structure has been established by x-ray crystallographic analysis of the corresponding iron complex.The thermal conversion of an o-chloromethyltoluene to a benzocyclobutene was first reported by Hart It is common practice in discussing the Diels-Alder and dimerization reactions of benzocyclobutenes to postulate an oxylylene as the reactive intermediate (5,7,8). Flynn and Michl found that o-xylylene, produced by photolysis of 1,4-dihydrophthalazine in a rigid glass at -196TC, has a strong absorption band at 373 nm (9). In an attempt to observe the presence of o-xylylenes in the gas phase, we have measured the UV absorption spectrum of4-methylbenzocyclobutene (7) in a stream of nitrogen at elevated temperatures. At 300 K, the typical solution absorption spectrum of4-methylbenzocyclobutene, centered at 282 nm, was observed. When the temperature in the absorption cell was raised, this band decreased and a new absorption band at 273 nm appeared. At 618 K, the absorption band at 282 nm, assigned to 4-methylbenzocyclobutene, disappeared and there was still no absorption in the region of 373 nm, suggesting the absence of any appreciable concentration of 4-methyl-o-xylylene (8). From a cold finger placed in the stream of exit gases, 4-methylbenzocyclobutene (7) was recovered in high yield. In addition, a small amount of crystals formed in the cooler region ofthe pyrolysis apparatus and these were identified as the mixture of isomers corresponding to the dimer 11 (10).This experiment, of course, does not provide reliable information regarding the dominant species in the gas phase at elevated temperatures other than to rule out 4-methyl-o-xylylene (8). In view of Errede's experiments in attempting to generate o-xylylene at various temperatures (11,12), it is tempting to postulate a thermal equilibrium between 8 and 9 in which, at elevated temperatures, it is the diradical 9 that proceeds to give 10 and 11. RESULTS AND DISCUSSION Appropriate bis(chloromethyl) derivatives undergo pyrolysis to give the corresponding benzo[1,2;4,5]dicyclobutenes. Although earlier reports indicate yields in this case of 24-30% (4, 6), we now find that pyrolysis of 5a on a scale of 30-150 g per run gives 6a in 53% yield, whereas 5b is converted to 6b in 36% yield. 6564The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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A study of the synthesis and properties of [26](1,2,3,4,5,6)cyclophane (superphane)

Cited by 84 publications

References 1 publication

Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Theoretical description of aromaticity in superphane cages

Gas-phase pyrolytic formation and dimerization of benzocyclobutenes: Synthesis of [2 ₄ ](1,2,4,5) cyclophane

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A study of the synthesis and properties of [26](1,2,3,4,5,6)cyclophane (superphane)

Cited by 84 publications

References 1 publication

Single Crystal Structure of Zeolite A (LTA) Containing Ag4Cl4Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Single Crystal Structure of Zeolite A (LTA) Containing Ag4Cl4Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Theoretical description of aromaticity in superphane cages

Gas-phase pyrolytic formation and dimerization of benzocyclobutenes: Synthesis of [2 4 ](1,2,4,5) cyclophane

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Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Single Crystal Structure of Zeolite A (LTA) Containing Ag₄Cl₄Nanoclusters and Reduced 1,3,5-Tripyrylium Dimers with Remarkably Short 2.43 Å Interplanar Spacings

Gas-phase pyrolytic formation and dimerization of benzocyclobutenes: Synthesis of [2 ₄ ](1,2,4,5) cyclophane