SPECTROELECTROCHEMISTRY OF CAROTENOIDS IN SOLUTION

The D0 --> D2 Optical absorption spectra of the cation radicals of beta-carotene and canthaxanthin in solution prepared using in situ spectroelectrochemical techniques at 300 K are reported. The weak and usually not reported D0 --> D1 transition of the cation radicals of the carotenoids are also observed in the optical spectra. The upper limit of the apparent molar extinction coefficient of carotenoid dications in solution is estimated to be on the order of 10(3) to 10(4). Under equilibrium conditions, the contribution of the dication absorption spectrum to that of the cation radical spectrum is negligible for the canthaxanthin cation radical and estimated to be approximately 10% for beta-carotene.