Abstract
Heating a solution of the circular bis-p-phenylene-34-crown-10 and a dumbbell-shaped bipyridinium component, terminated at both ends by 4-R- phenyl-bis(4-tert-butyl-phenyl)methane-based stoppers, affords the corresponding [2]rotaxane when R is equal to H, Me, and Et, following the slippage of the macrocycle over the stoppers of the dumbbell. By contrast, no [2]rotaxane is obtained when R is equal to i-Pr. Computational investigations with the AMBER* force field provide an explanation of this dramatic substitutent effect. The phenomenon was simulated by the passage of the bis- p-phenylene-34-crown-10 macrocycle over four 4-R-phenyl-bis(4-tert-butyl- phenyl)methane model stoppers. For R equal to H, Me, Et, and i-Pr, there are two main energy barriers which have to be surpassed in order to permit the passage of the macrocycle over the bulky stoppers. When R is equal to H or Me, the rate-determining step is the passage of the macrocycle over a t-Bu- C6H4- ring. By contrast, when R is equal to Et or i-Pr, the rate- determining step becomes the passage of the macrocycle over the R-C6H4- ring. However, when R is equal to i-Pr, the resulting energy barrier is more than 21 kcal mol-1 higher than in the case of any of the other stoppers. These results are in good agreement with the experimental observations and provide a quantitative explanation for the rigorous size complementarily requirements between macrocycle and stopper which have been observed experimentally.
| Original language | English |
|---|---|
| Pages (from-to) | 9318-9322 |
| Number of pages | 5 |
| Journal | Journal of the American Chemical Society |
| Volume | 120 |
| Issue number | 36 |
| DOIs | |
| State | Published - Sep 16 1998 |
| Externally published | Yes |
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ASJC Scopus subject areas
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Cite this
The mechanism of the slippage approach to rotaxanes. Origin of the 'all- or-nothing' substituent effect. / Raymo, Francisco; Houk, K. N.; Stoddart, J. Fraser.
In: Journal of the American Chemical Society, Vol. 120, No. 36, 16.09.1998, p. 9318-9322.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The mechanism of the slippage approach to rotaxanes. Origin of the 'all- or-nothing' substituent effect
AU - Raymo, Francisco
AU - Houk, K. N.
AU - Stoddart, J. Fraser
PY - 1998/9/16
Y1 - 1998/9/16
N2 - Heating a solution of the circular bis-p-phenylene-34-crown-10 and a dumbbell-shaped bipyridinium component, terminated at both ends by 4-R- phenyl-bis(4-tert-butyl-phenyl)methane-based stoppers, affords the corresponding [2]rotaxane when R is equal to H, Me, and Et, following the slippage of the macrocycle over the stoppers of the dumbbell. By contrast, no [2]rotaxane is obtained when R is equal to i-Pr. Computational investigations with the AMBER* force field provide an explanation of this dramatic substitutent effect. The phenomenon was simulated by the passage of the bis- p-phenylene-34-crown-10 macrocycle over four 4-R-phenyl-bis(4-tert-butyl- phenyl)methane model stoppers. For R equal to H, Me, Et, and i-Pr, there are two main energy barriers which have to be surpassed in order to permit the passage of the macrocycle over the bulky stoppers. When R is equal to H or Me, the rate-determining step is the passage of the macrocycle over a t-Bu- C6H4- ring. By contrast, when R is equal to Et or i-Pr, the rate- determining step becomes the passage of the macrocycle over the R-C6H4- ring. However, when R is equal to i-Pr, the resulting energy barrier is more than 21 kcal mol-1 higher than in the case of any of the other stoppers. These results are in good agreement with the experimental observations and provide a quantitative explanation for the rigorous size complementarily requirements between macrocycle and stopper which have been observed experimentally.
AB - Heating a solution of the circular bis-p-phenylene-34-crown-10 and a dumbbell-shaped bipyridinium component, terminated at both ends by 4-R- phenyl-bis(4-tert-butyl-phenyl)methane-based stoppers, affords the corresponding [2]rotaxane when R is equal to H, Me, and Et, following the slippage of the macrocycle over the stoppers of the dumbbell. By contrast, no [2]rotaxane is obtained when R is equal to i-Pr. Computational investigations with the AMBER* force field provide an explanation of this dramatic substitutent effect. The phenomenon was simulated by the passage of the bis- p-phenylene-34-crown-10 macrocycle over four 4-R-phenyl-bis(4-tert-butyl- phenyl)methane model stoppers. For R equal to H, Me, Et, and i-Pr, there are two main energy barriers which have to be surpassed in order to permit the passage of the macrocycle over the bulky stoppers. When R is equal to H or Me, the rate-determining step is the passage of the macrocycle over a t-Bu- C6H4- ring. By contrast, when R is equal to Et or i-Pr, the rate- determining step becomes the passage of the macrocycle over the R-C6H4- ring. However, when R is equal to i-Pr, the resulting energy barrier is more than 21 kcal mol-1 higher than in the case of any of the other stoppers. These results are in good agreement with the experimental observations and provide a quantitative explanation for the rigorous size complementarily requirements between macrocycle and stopper which have been observed experimentally.
UR - http://www.scopus.com/inward/record.url?scp=0032538060&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032538060&partnerID=8YFLogxK
U2 - 10.1021/ja9806229
DO - 10.1021/ja9806229
M3 - Article
AN - SCOPUS:0032538060
VL - 120
SP - 9318
EP - 9322
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 36
ER -