ESR of triplet states of chlorophylls a,b, c1, c2 and bacteriochlorophyll a. Applications of ZFS and electron spin polarization to photosynthesis

ZFS parameters for the title chlorophylls in both ordinary and fully deuterated form have been determined under experimental conditions that allow the aggregation state of the chlorophylls to be specified. The triplet state spectra are polarized. The electron spin polarization (ESP) can be analyzed by a simple scheme, and is found to be sensitive to the aggregation state of the chlorophyll. Comparison of in vivo and in vitro bacteriochlorophyll spectra supports the chlorophyll special pair proposal for the structure of in vivo photo-reactive chlorophyll.