Ligand effects on the triplet state of chlorophyll

Abstract Laser excitation at 457.9 and 514.5 nm of a frozen solution of chlorophyll a in n -octane produces two fluorescence peak maxima at 2 K that may be assigned to two distinct monomeric chlorophyll species. Utilizing zero-field fluorescence-detected magnetic resonance the triplet state properties of the two chlorophyll species may be assigned to the monoligated and biligated chlorophyll monomer in which water serves as the ligand coordinated to the magnesium metal center.