Demetalation kinetics of the zinc chlorophyll derivative possessing two formyl groups: effects of formyl groups conjugated to the chlorin macrocycle on physicochemical properties of photosynthetic pigments

作者：Sadaoka Kana; Oba Toru; Tamiaki Hitoshi; Kashimura Shigenori; Saga Yoshitaka^*

来源：Journal of Porphyrins and Phthalocyanines, 2013, 17(11): 1120-1128.

DOI：10.1142/S1088424613500788

• chlorophyll
• formyl group
• hammett constant
• pheophytinization

Demetalation kinetics of zinc chlorophyll derivative 1 possessing two formyl groups directly linked to the A-and B-rings of the chlorin macrocycle, which was synthesized from chlorophyll b, was examined under acidic conditions and compared with those of Zn chlorins 2 and 3 possessing a single formyl group in the A-and B-ring, respectively, as well as Zn chlorin 4 lacking any formyl group to unravel the substitution effects on demetalation properties of chlorophyllous pigments. Demetalation kinetics of diformylated Zn chlorin 1 was slower than those of monoformylated Zn chlorins 2 and 3, indicating that the effect of the electron-withdrawing formyl group on demetalation kinetics was amplified by introduction of two formyl groups to the chlorin macrocycle. High correlations were observed between demetalation rate constants of Zn chlorins 1-4 and the sum of Hammett sigma parameters of the 3- and 7-substituents on the chlorin macrocycle, indicating that the combination of electron-withdrawing abilities of the substituents linked directly to the cyclic tetrapyrrole was responsible for demetalation properties of zinc chlorophyll derivatives.

• 出版日期2013-11