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Title: Compressing Double [7]Helicene by Successive Charging with Electrons
Abstract

Chemical reduction of a benzo‐fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of1. The doubly‐reduced helicene12−has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes,13−and14−, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb+ions each, leaving three remaining Rb+ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in14−vs. 2.09 Å in1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in1to 20.7° in14−. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data.

 
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Award ID(s):
2003411 1608628 1726724 1834750
NSF-PAR ID:
10171987
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie International Edition
Volume:
59
Issue:
37
ISSN:
1433-7851
Page Range / eLocation ID:
p. 15923-15927
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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