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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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Exciton coupling chirality in helicene-porphyrin conjugates
Enantiopure helicene-porphyrin conjugates were prepared. They show strong changes in their circular dichroic response as compared to classical helicene derivatives, with highly intense bisignate Exciton Coupling (EC) signal and Δ ε values up to 680 M −1 cm −1 for the Soret band. They also display circularly polarized fluorescence in the (far-)red region, with dissymmetry factors up to 7 × 10 −4 .
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- Award ID(s):
- 1855470
- PAR ID:
- 10346707
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 57
- Issue:
- 82
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 10743 to 10746
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1CC03314J
