Natural and Magnetic Circular Dichroism Soectra of Selenofenchone. Evidence for a Singlet-Triplet Component of the n -> ?* Transition of Selenoketones

Article abstract of DOI:10.1021/j100239a015

Blue (-)-selenofenchone (1) is observed to give a negative long-wavelength Cotton effect (CE) Δε₅₇₃^max = -0.86, in addition to a series of CE's down to 190 nm, Δε₂₇₀^max = -5.21, Δε₂₃₂^max = +4.90, in its circular dichroism (CD) spectrum measured in n-heptane.The long-wavelength CD (573 nm) and UV (625 nm) λ_max of 1 are found surprisingly well separated.Support for the singlet-triplet nature of this electronic transition may be found in a sharp positive magnetic CD band centered near 630 nm in (+/-)-selenofenchone.The CD and UV data are compared with those of thiofenchone (2) and fenchone (3).