Restricted Rotation Involving the Tetrahedral Carbon. LXIV. Barriers to Rotation of <i>s</i>-Alkyl Groups in 9-<i>s</i>-Alkyl-8,13-difluoro-1,4-dimethyl- and 1,2,3,4-tetrachloro-triptycenes

Ōki, Michinori; Nishino, Masami; Kaieda, Kazuihiro; Nakashima, Takafumi; Toyota, Shinji

doi:10.1246/bcsj.74.357

Cited by 5 publications

(3 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have found, through molecular modeling and experimental studies, that modified triptycene-derived compounds can be used to directly measure the strength of arene−arene interactions in the parallel-displaced configuration in organic solvents. Oki and co-workers pioneered the use of the triptycene molecular system in the study of weak molecular interactions. , No work related to π-stacking, however, has been reported using this system. The conformational equilibrium between the symmetrical anti form and the chiral syn forms in the triptycene molecular system ( 1 , Figure ) can be measured by low-temperature NMR spectroscopy by taking advantage of the slow rotation of the C9-benzyl carbon−carbon bond in compound 1 .…”

Section: Resultsmentioning

confidence: 99%

The Strength of Parallel-Displaced Arene−Arene Interactions in Chloroform

2005

View full text Add to dashboard Cite

[reaction: see text] Triptycene-derived compounds have been prepared to serve as conformational equilibrium reporters for direct measurements of arene-arene interactions in the parallel-displaced orientation. A series of such compounds bearing arenes with different substituents were synthesized, and the ratios of the syn and anti conformers were determined by variable-temperature NMR spectroscopy. The syn conformer allows attached arenes to interact with each other while the anti conformer does not. The free energies derived from the syn/anti ratios in chloroform range from slightly positive (0.2 kcal/mol) to considerably negative (-0.98 kcal mol) values. The interactions between the arenes bearing electron-donating groups (EDG) are either negligible or slightly repulsive, while the interactions between arenes bearing electron-withdrawing groups (EWG) are attractive. Intermediate free energy values are obtained for those compounds bearing arenes with one EDG and one EWG.

show abstract

Section: Resultsmentioning

confidence: 99%

The Strength of Parallel-Displaced Arene−Arene Interactions in Chloroform

2005

View full text Add to dashboard Cite

show abstract

“…For Trip(Me)−PIM, our results suggest that the methyl group undergoes reorientation, but that the reorientation is significantly more hindered than is typical for methyl groups in organic solids. Solution state NMR studies on triptycenes substituted with an isopropyl group at the bridgehead show that the activation energy for rotation about the C−CH(CH 3 ) 2 bond is in excess of 75 kJ mol −1 . − Hence, it can be concluded that ethyl and isopropyl side-chains are unable to alter their conformation in order to occupy free volume and can be considered as part of the rigid framework of the PIM, whereas longer n- alkyl side-chains have sufficient conformational freedom to fill the free volume.…”

Section: Discussionmentioning

confidence: 99%

Triptycene-Based Polymers of Intrinsic Microporosity: Organic Materials That Can Be Tailored for Gas Adsorption

et al. 2010

View full text Add to dashboard Cite

We report the synthesis and properties of network polymers of intrinsic microporosity (network−PIMs) derived from triptycene monomers that possess alkyl groups attached to their bridgehead positions. Gas adsorption can be controlled by the length and branching of the alkyl chains so that the apparent BET surface area of the materials can be tuned within the range 618−1760 m2 g−1. Shorter (e.g., methyl) or branched (e.g., isopropyl) alkyl chains provide the materials of greatest microporosity, whereas longer alkyl chains appear to block the microporosity created by the rigid organic framework. The enhanced microporosity, in comparison to other PIMs, originates from the macromolecular shape of the framework, as dictated by the triptycene units, which helps to reduce intermolecular contact between the extended planar struts of the rigid framework and thus reduces the efficiency of packing within the solid. The hydrogen adsorption capacities of the triptycene-based PIMs with either methyl or isopropyl substituents are among the highest for purely organic materials at low or moderate presures (1.83% by mass at 1 bar/77K; 3.4% by mass at 18 bar/77 K). The impressive hydrogen adsorption capacity of these materials is related to a high concentration of subnanometre micropores, as verified by Horvath−Kawazoe analysis of low-pressure nitrogen adsorption data.

show abstract

“…Returning to the opposite end of the folding molecule spectrum, minimal synthetic folding systems, such as the 'torsion balance' molecules developed by Oki and Wilcox have been extensively used for the study of non-covalent interactions. [52][53][54][55] Both of these systems have been exploited by other investigators. [56][57][58][59] Distinct foldamer signals in NMR spectra indicate that folding is a two-state event on the NMR timescale.…”

Section: Folding Moleculesmentioning

confidence: 99%