Chlorophyll-a derivatives possessing an un/mono/disubstituted methylene moiety at the 13 1 -position were prepared by (un)substituted methylation of the 13-carbonyl group and successive dehydration. Substitution of the 13 1 -oxo to the methylene group slightly blue-shifted electronic absorption and emission bands in a solution and decreased chemical stability to give an oxidation product cleaved at the E-ring. Further mono/disubstitution at the methylene terminal increased wavelengths of absorption and emission maxima as well as oxidative tolerance.
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