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Scientific article
English

Triggering Emission with the Helical Turn in Thiadiazole-Helicenes

Published inChemistry, vol. 23, no. 2, p. 437-446
Publication date2017
Abstract

Introduction of heterocycles in the helical skeleton of helicenes allows modulation of their redox, chiroptical and photophysical properties. Herein, we describe the straightforward preparation and structural characterization by single crystal X-ray diffraction of thiadiazole-[7]helicene, which has been resolved into (M) and (P) enantiomers by chiral HPLC, together with its S-shaped double [4]helicene isomer, as well as the smaller congeners thiadiazole-[5]helicene and benzothiadiazole-anthracene. A copper(II) complex with two thiadiazole-[5]helicene ligands has been structurally characterized and it shows the presence of both (M) and (P) isomers coordinated to the metal centre. The emission properties of the unprecedented heterohelicenes are highly dependent on the helical turn, as the [7]- and [5]helicene are poorly emissive, whereas their isomers, that is, the S-shaped double [4]helicene and thiadiazole-benzanthracene, are luminescent, with quantum efficiencies of 5.4% and 6.5%, respectively. DFT calculations suggest a quenching of the luminescence of enantiopure [7]helicenes through an intersystem crossing mechanism arising from the relaxed excited S1 state.

Keywords
  • chirality
  • circular dichroism
  • density functional calculations
  • helicenes
  • heterocycles
Citation (ISO format)
BIET, Thomas et al. Triggering Emission with the Helical Turn in Thiadiazole-Helicenes. In: Chemistry, 2017, vol. 23, n° 2, p. 437–446. doi: 10.1002/chem.201604471
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ISSN of the journal0947-6539
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