Ultraviolet-visible linear dichroism spectroscopy of 9-oxa-2,3-4'-methoxy benzo bicyclo [4,3,0] non-1(6)-ene-7,8-dione

Ultraviolet-visible (UV-VIS) linear dichroism (LD) spectra of the title compound in stretched polyethylene (PE) film are reported. The spectrum is resolved into four electronic transitions differently polarized. The first transition at lambda(max) = 396 nm is polarized along the long axis of the molecule, the second transition at lambda(max) = 360 nm, which is hidden by the first one in solution, is clearly isolated in the LD spectrum, and is polarized along some intermediate direction between the long and the in-plane short axis of the molecule. The third transition at lambda(max) = 290 nm, and the fourth one at lambda(max) = 256 nm are polarized perpendicularly to each other, they correspond respectively to the L-1(b) and L-1(a) transitions of the benzene part. The obtained LD results are consistent with the CNDO/S calculations investigated in this work. (C) 1997 Elsevier Science B.V.