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Self-assembled, helically stacked anionic aggregates of 2,5,8,11-tetra-tert-butylcycloocta[1,2,3,4-def,5,6,7,8-d'e'f']bisbiphenylene, stabilized by electrostatic interactions

Citation:

Shenhar, R. ; Wang, H. ; Hoffman, R. E. ; Frish, L. ; Avram, L. ; Willner, I. ; Rajca, A. ; Rabinovitz, M. Self-assembled, helically stacked anionic aggregates of 2,5,8,11-tetra-tert-butylcycloocta[1,2,3,4-def,5,6,7,8-d'e'f']bisbiphenylene, stabilized by electrostatic interactions. Journal of the American Chemical Society 2002, 124, 4685-4692.

Date Published:

MAY 1

Abstract:

Tetraanions of alkyl-substituted derivatives of cycloocta[1,2,3,4-def,5,6,7,8-d'e'f']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 >15 kcal mol-1 in the tetramer.

Notes:

7. Helical supramolecular tetramer held by electrostatic interactions

See also: PhD papers (1997-2002)
Last updated on 02/08/2019