Phthalocyanine as a Bioinspired Model for Chlorophyll f‐Containing Photosystem II Drives Photosynthesis into the Far‐Red Region

• Published in: Angewandte Chemie International Edition Vol. 60; no. 22; pp. 12284 - 12288
• Main Authors: Follana‐Berná, Jorge, Farran, Rajaa, Leibl, Winfried, Quaranta, Annamaria, Sastre‐Santos, Ángela, Aukauloo, Ally
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 25.05.2021; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Absorption; bioinspired models; Biomimetics; Chemistry; Chemistry, Multidisciplinary; Chlorophyll; chlorophyll f; Cofactors; Electron transfer; far-red region; Imidazole; Oxidation; Photosynthesis; Photosystem II; phthalocyanine; Physical Sciences; Pigments; Science & Technology; II; phthalocyanine; chlorophyll f; bioinspired models; far-red region; photosystem  photosystem II
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202101051

The textbook explanation that P680 pigments are the red limit to drive oxygenic photosynthesis must be reconsidered by the recent discovery that chlorophyll f (Chlf)‐containing Photosystem II (PSII) absorbing at 727 nm can drive water oxidation. Two different families of unsymmetrically substituted Zn phthalocyanines (Pc) absorbing in the 700–800 nm spectral window and containing a fused imidazole‐phenyl substituent or a fused imidazole‐hydroxyphenyl group have been synthetized and characterized as a bioinspired model of the Chlf/TyrosineZ/Histidine190 cofactors of PSII. Transient absorption studies in the presence of an electron acceptor and irradiating in the far‐red region evidenced an intramolecular electron transfer process. Visible and FT‐IR signatures indicate the formation of a hydrogen‐bonded phenoxyl radical in ZnPc II‐OH. This study sets the foundation for the utilization of a broader spectral window for multi‐electronic catalytic processes with one of the most robust and efficient dyes. A phthalocyanine chromophore absorbing in the far‐red region with a tyrosine residue hydrogen bonded to an imidazole moiety provides the first example of a bioinspired model for the recent discovery that chlorophyll f‐containing Photosystem II absorbing in the far‐red limit at 727 nm can drive the four‐electron water oxidation.