Conformational Ordering of Apolar, Chiral m-Phenylene Ethynylene Oligomers

Organic Letters

Volumn 2, Issue 11, 2000, Pages 1525-1528

  Brunsveld, Luc ^b   Prince, Ryan B ^c   Meijer, E W ^b   Moore, Jeffrey S ^a  

^a UNIVERSITY OF ILLINOIS AT URBANA CHAMPAIGN   (United States)

^b EINDHOVEN UNIVERSITY OF TECHNOLOGY   (Netherlands)

^c 3M COMPANY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0002191781     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0056877     Document Type: Article

References (22)

1. Reichardt, C. Solvents and Solvent Effects in Organic Chemistry; VCH: New York, 1990.
2. Williams, C.; Bochard, F.; Frisch, H. L. Ann. Rev. Phys. Chem. 1981, 32, 433.
3. (a) Dill, K. A.; Bromberg, S.; Yue, K.; Friebig, K. M.; Yee, D. P.; Thomas, P. D.; Chan, H. S. Protein Sci. 1995, 4, 561-602.
4. (b) Chan, H. S.; Dill, K. A. Macromolecules 1989, 22, 4559-4573.
5. (c) Camacho, C. J.; Thirumalai, D. Phys. Rev. Lett. 1993, 71, 2505-2508.
6. (a) Roy, S.; Ratnaswamy, G.; Boice, J. A.; Fairman, R.; McLendon, G.; Hecht, M. H. J. Am. Chem. Soc. 1997, 119, 5302-5306.
7. (b) Wolynes, P. G. Nat. Struct. Biol. 1997, 4, 871-874.
8. (a) Nelson, J. C.; Saven, J. G.; Moore, J. S.; Wolynes, P. G. Science 1997, 277, 1793.
9. (b) Prince, R. B.; Saven, J. G.; Wolynes, P. G.; Moore, J. S. J. Am. Chem. Soc. 1999, 121, 3114.
10. Prince, R. B.; Brunsveld, L.; Meijer, E. W.; Moore, J. S. Angew. Chem. Int. Ed. 2000, 39, 228.
11. Zhang, J.; Pesak, D. J.; Ludwick, J. J.; Moore, J. S. J. Am. Chem. Soc. 1994, 116, 4227.
12. Schouten, P. G.; van der Pol, J. F.; Zwikker, J. W.; Drenth, W.; Picken, S. J. Mol. Cryst. Liq. Cryst. 1991, 195, 291.
13. The shorter oligomers (1, n = 2, 4, and 6) have been studied and show no solvent dependent conformational transitions. They are present in a random coil conformation under all conditions.
14. It was determined that for 1 (n = 18) in heptane at concentrations above 1 μM, Beer's law was not followed anymore and a decrease of the molar ellipticity and broadening with concomitant blue shift of the absorbance maximum could be observed.
15. The Δ∈ of 1 (n = 18) is constant up to concentrations of ca. 1 μM but significantly increases at higher concentrations.
16. The terms "poor solvent" and "good solvent" are used in the usual polymer chemistry sense. See: Flory, P. J. Principles of Polymer Chemistry; Cornell University Press: Ithaca, 1953; p 424.
17. The onset of the twist sense bias for the polar oligomers 1 lies at a solvent composition of at least 50% chloroform in acetonitrile (dodecamer). whereas this is approximately 10% chloroform in heptane for the apolar oligomers. The folding of the polar oligomers also occurs at solvent compositions that consist of a higher chloroform percentage (70%) than for the apolar oligomers (∼50%).
18. The broadening and blue shift of absorbance maximum that occur at increasing concentration or lower temperatures are typical for an intermolecular aggregation process. See: Cornelissen, J. J. L. M.; Peeters, E.; Janssen, R. A. J.; Meijer, E. W. Acta Polym. 1998, 49, 471.
19. Aggregation via π-π stacking is highly favorable in alkanes, for an example, see: Palmans, A. R. A.; Vekemans, J. A. J. M.; Havinga, E. E.; Meijer, E. W. Angew. Chem., Int. Ed. Engl. 1997, 36, 2648.
20. (a) Langeveld-Voss, B. M. W. Ph.D. Thesis, Eindhoven University of Technology, 1999.
21. (b) Pieterse, K.; Meijer, E. W. Eindhoven University of Technology, unpublished results.
22. The polar oligomers 1 do not show this time dependence, consistent with its behavior being a purely intramolecular phenomenon.