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Title: Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes

Abstract

9,10,11,20,21,22-hexaphenyltetrabenzo[a,c,l,n]pentacene (2) and a dimethyl derivative (2m) were prepared by the reaction of 1,3-diphenylphenanthro[9,10-c]furan with bisaryne equivalents generated from 1,2,4,5-tetrabromo-3,6-diarylbenzenes in the presence of n-butyllithium, followed by deoxygenation of the double adducts with low-valent titanium. Both are bright red solids with a strong orange fluorescence in solution. The X-ray structures of these compounds show them to be the most highly twisted polycyclic aromatic hydrocarbons known. Compound 2 has an end-to-end twist of 144{sup o}, and the two crystallographically independent molecules of 2m have twists of 138{sup o} and 143{sup o}. Both molecules were resolved by chromatography on chiral supports, and the pure enantiomers have extremely high specific rotations (for 2, [{alpha}]{sub D} = 7400{sup o}; for 2m, 5600{sup o}), but the molecules racemize slowly at room temperature ({Delta}G{sup {double_dagger}}{sub rac} = 24 kcal/mol). Both the experimental geometry and the observed racemization barrier for 2 are in good agreement with computational studies of the molecule at a variety of levels. Attempts to prepare compound 2 by reaction of tetraphenylbenzyne with 9,10,12,13-tetraphenyl-11-oxacyclopenta[b]triphenylene (3, a twisted isobenzofuran) gave no adducts, and attempts to prepare tetradecaphenylpentacene by reaction of hexaphenylisobenzofuran (11) with bisaryne equivalents gave only monoadducts.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930155
Report Number(s):
BNL-80813-2008-JA
Journal ID: ISSN 0002-7863; JACSAT; TRN: US200822%%1206
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 128
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CONDENSED AROMATICS; SYNTHESIS; MOLECULAR STRUCTURE; POLYCYCLIC AROMATIC HYDROCARBONS; RACEMIZATION; RESOLUTION; SHAPE; national synchrotron light source

Citation Formats

Lu,J., Ho, D., Vogelaar, N., Kraml, C., Bernhard, S., Byme, N., Kim, L., and Pascal, Jr., R. Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes. United States: N. p., 2006. Web. doi:10.1021/ja065935f.
Lu,J., Ho, D., Vogelaar, N., Kraml, C., Bernhard, S., Byme, N., Kim, L., & Pascal, Jr., R. Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes. United States. doi:10.1021/ja065935f.
Lu,J., Ho, D., Vogelaar, N., Kraml, C., Bernhard, S., Byme, N., Kim, L., and Pascal, Jr., R. Sun . "Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes". United States. doi:10.1021/ja065935f.
@article{osti_930155,
title = {Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes},
author = {Lu,J. and Ho, D. and Vogelaar, N. and Kraml, C. and Bernhard, S. and Byme, N. and Kim, L. and Pascal, Jr., R.},
abstractNote = {9,10,11,20,21,22-hexaphenyltetrabenzo[a,c,l,n]pentacene (2) and a dimethyl derivative (2m) were prepared by the reaction of 1,3-diphenylphenanthro[9,10-c]furan with bisaryne equivalents generated from 1,2,4,5-tetrabromo-3,6-diarylbenzenes in the presence of n-butyllithium, followed by deoxygenation of the double adducts with low-valent titanium. Both are bright red solids with a strong orange fluorescence in solution. The X-ray structures of these compounds show them to be the most highly twisted polycyclic aromatic hydrocarbons known. Compound 2 has an end-to-end twist of 144{sup o}, and the two crystallographically independent molecules of 2m have twists of 138{sup o} and 143{sup o}. Both molecules were resolved by chromatography on chiral supports, and the pure enantiomers have extremely high specific rotations (for 2, [{alpha}]{sub D} = 7400{sup o}; for 2m, 5600{sup o}), but the molecules racemize slowly at room temperature ({Delta}G{sup {double_dagger}}{sub rac} = 24 kcal/mol). Both the experimental geometry and the observed racemization barrier for 2 are in good agreement with computational studies of the molecule at a variety of levels. Attempts to prepare compound 2 by reaction of tetraphenylbenzyne with 9,10,12,13-tetraphenyl-11-oxacyclopenta[b]triphenylene (3, a twisted isobenzofuran) gave no adducts, and attempts to prepare tetradecaphenylpentacene by reaction of hexaphenylisobenzofuran (11) with bisaryne equivalents gave only monoadducts.},
doi = {10.1021/ja065935f},
journal = {Journal of the American Chemical Society},
number = ,
volume = 128,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
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