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The Effects of Ring Strain on Cyclic Tetraaryl[5]cumulenes
Bozheng Sun1, Meagan S Oakley1, Kota Yoshida2
1Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
Abstract:
Cyclic tetraaryl[5]cumulenes (1 a-f) have been synthesized and studied as a function of increasing ring strain. The magnitude of ring strain is approximated by the extent of bending of the cumulenic core as assessed by a combination of X-ray crystallographic analysis and DFT calculations. Trends are observed in 13 C NMR, UV-vis, and Raman spectra associated with ring strain, but the effects are small. In particular, the experimental HOMO-LUMO gap is not appreciably affected by bending of the [5]cumulene framework from ca. 174° (λmax =504 nm) in 1 a to ca. 178° (λmax =494 nm) in 1 f.
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