@article { ISI:000175227600037,
	title = {Self-assembled, helically stacked anionic aggregates of 2,5,8,11-tetra-tert-butylcycloocta[1,2,3,4-def,5,6,7,8-d\&$\#$39;e\&$\#$39;f\&$\#$39;]bisbiphenylene, stabilized by electrostatic interactions},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {17},
	year = {2002},
	note = {[["fid":"23985","view_mode":"default","type":"media","attributes":"style":"width: 597px; height: 250px;","alt":"7. Helical supramolecular tetramer held by electrostatic interactions","title":"7. Helical supramolecular tetramer held by electrostatic interactions","class":"media-element file-default "]]},
	month = {MAY 1},
	pages = {4685-4692},
	publisher = {AMER CHEMICAL SOC},
	type = {Article},
	address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
	abstract = {Tetraanions of alkyl-substituted derivatives of cycloocta[1,2,3,4-def,5,6,7,8-d{\textquoteright}e{\textquoteright}f{\textquoteright}]bisbiphenylene (BPD) and their counter lithium cations self-assemble to form helically stacked assemblies, including a dimer, a trimer, and a tetramer. NMR self-diffusion measurements and unprecedented magnetic shielding effects for the sandwiched lithium cations support their aggregated nature. The D2-tetramer assembly is fully characterized by NMR spectroscopy, providing unequivocal evidence for a helix of four tetraanionic BPD layers with an estimated relative twist angle of about 45degrees and interlayer spacing of ca. 4 Angstrom. The barrier for racemization through the in-plane inter-deck rotation is DG200(double dagger) = 9.5 +/- 0.2 kcal mol-1 in the dimer compared to \&gt;15 kcal mol-1 in the tetramer.},
	issn = {0002-7863},
	doi = {10.1021/ja012140u},
	author = {Shenhar, R and Wang, H and Hoffman, RE and Frish, L and Avram, L. and Willner, I. and Rajca, A and Rabinovitz, M}
}
