Band gap of carbon-sulfur [N]helicenes.
Asymmetric synthesis of (-)-[9]helicene, as well as preparation of its lower homologues, completes the series of carbon-sulfur [5]-, [7]-, [9]-, and [11]helicenes. Spectroscopic and electrochemical studies of this series provide an absorption onset-based band gap, E(g) = 3.40 eV, for a cross-conjugated (C(2)S)(n) helix; this value may be compared to E(g) = 3.59 eV obtained from TD-DFT computed excitation energies for a series of dimethyl-substituted [n]helicenes (n ≤ 31).
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
Makoto
M
Miyasaka
Maren
M
Pink
Arnon
A
Olankitwanit
Suchada
S
Rajca
Andrzej
A
Rajca