Covalent heterodyads of synthetic chlorophyll derivatives linked with linear rigid substituents at the 20-positions constructing photoexcited energy transfer systems

A series of meso‐biphenyl linked chlorin and bacteriochlorin dimers, derived from naturally occurring chlorophyll (Chl‐a) and bacteriochlorophyll (BChl‐a) were synthesized in 32 % to 44 % yields and characterized, as photosynthetic antenna mimics, and a new class of singlet oxygen producing agents. The dimers are characterized by absorption, fluorescence, electrochemical, spectroelectrochemical and computational methods to evaluate their physico‐chemical properties, and to identify ground and excited state interactions. Evidence of excited energy exchange among the chromophores in the dimer is derived from femtosecond transient absorption spectral studies. Rate constants for excitation hopping were in the order of 1011 s−1, indicating occurrence of efficient processes. Nanosecond transient absorption studies confirmed relaxation of the singlet excited chlorin and bacteriochlorin dimers to their corresponding triplet states (3Chl* and 3Bchl*). As predicted by the established energy level diagrams, both 3Chl* and 3Bchl* are shown to be capable of producing singlet oxygen with appreciable quantum yields (ϕSO∼0.3).

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Meso‐Biphenyl‐Linked, Near‐ and Far‐Infrared Emitting, Chlorin and Bacteriochlorin Dimers: Synthesis, Excitation Transfer, and Singlet Oxygen Production

Seetharaman

Dukh

Tabaczynski

et al. 2021

ChemPlusChem

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Synthesis of Fluorinated Chlorophylls‐a and Their Bio/Physico‐Chemical Properties

2020

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Pheophytin(Pheo)‐a as the free base of chlorophyll(Chl)‐a, was fluorinated at the 20‐position using N‐fluorobenzenesulfonimide, followed by insertion of a magnesium cation at the central position to afford 20‐fluoro‐Chl‐a. On the other hand, 32,32‐difluoro‐Chl‐a was obtained from Pheo‐d possessing the 3‐formyl group by the Wittig reaction using (triphenylphosphonio)difluoroacetate and the successive magnesium insertion. The synthetic 20‐fluoro‐ and 32,32‐difluoro‐Chls‐a showed similar optical properties and enzymatic hydrolysis of the phytyl ester to original (intact) Chl‐a. By contrast, their 132‐stereochemical inversion (epimerization) occurred more rapidly, and the removal of their central magnesium (pheophytinization) was more tolerant than Chl‐a due to the electronic effect of the fluorine atom(s) through the chlorin π‐system in a molecule. Since a fluorine atom is comparable in the size to a hydrogen atom, these chemically stable fluorinated Chls‐a are promising as the synthetic alternatives to naturally occurring Chl‐a, and are useful for the structural and functional investigation in oxygenic phototrophs.

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Panchromatic Pt/TiO2-Based Photocatalysts Sensitized with Carboxylated Chlorin Dyads for Water Splitting Hydrogen Evolution

Zheng

Liu

et al. 2023

Applied Surface Science

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Covalent heterodyads of synthetic chlorophyll derivatives linked with linear rigid substituents at the 20-positions constructing photoexcited energy transfer systems

Cited by 6 publications

References 67 publications

Meso‐Biphenyl‐Linked, Near‐ and Far‐Infrared Emitting, Chlorin and Bacteriochlorin Dimers: Synthesis, Excitation Transfer, and Singlet Oxygen Production

Meso‐Biphenyl‐Linked, Near‐ and Far‐Infrared Emitting, Chlorin and Bacteriochlorin Dimers: Synthesis, Excitation Transfer, and Singlet Oxygen Production

Synthesis of Fluorinated Chlorophylls‐a and Their Bio/Physico‐Chemical Properties

Panchromatic Pt/TiO2-Based Photocatalysts Sensitized with Carboxylated Chlorin Dyads for Water Splitting Hydrogen Evolution

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