FLUORESCENCE SPECTRA AND ZERO‐FIELD MAGNETIC RESONANCE OF CHLOROPHYLL <i>a</i>‐WATER COMPLEXES

Abstract

Abstract. –Fluorescence detected magnetic resonance (FDMR) and fluorimetry have been used to study chlorophyll‐water complexes at T = 4.2 K. By combining these methods, zero‐field splitting (ZFS)‐parameters can be assigned to the triplet state of the various species. It is found that these parameters decrease upon aggregation and/or complexation. These results can be rationalized by using a simple free‐electron model for chlorophyll including excitonic interaction. Evidence is presented favouring a structure recently proposed by Shipman and Katz for a chlorophyll‐dimer involving hydrogen‐bonded water, present in non‐polar solutions at low temperature with spectral properties similar to those of chlorophyll in vivo.