Furan‐ and Thiophene‐Based Auxochromes Red‐shift Chlorin Absorptions and Enable Oxidative Chlorin Polymerizations

Abstract

The de novo syntheses of chemically stable chlorins with five‐membered heterocyclic (furane, thiophene, formylfurane and formylthiophene) substituents in selected meso‐ and β‐positions are reported. Heterocycle incorporation in the 3‐ and 13‐positions shifted the chlorin absorption and emission to the red (up to λ em=680 nm), thus these readily incorporated substituents function analogously to auxochromes present in chlorophylls, for example, formyl and vinyl groups. Photophysical, theoretical and X‐ray crystallographic experiments revealed small but significant differences between the behavior of the furan‐ and the thiophene‐based auxochromes. Four regioisomeric bis‐thienylchlorins (3,10; 3,13, 3,15 and 10,15) were oxidatively electropolymerized; the chlorin monomer geometry had a profound impact on the polymerization efficiency and the electrochemical properties of the resulting material. Chemical co‐polymerization of 3,13‐bis‐thienylchlorin with 3‐hexylthiophene yielded an organic‐soluble red‐emitting polymer.

Intramolecular singlet fission and triplet exciton harvesting in tetracene oligomers for solar energy conversion

“…Thirdly, the introduction of heterocycles (such as thiophene and pyridine) in the tetracene framework can also increase its stability. 218,222 The stability of the oligomers prepared with the modied tetracene will be enhanced signicantly. Additionally, to maximize the efficiency of solar cells, it is necessary to broaden the absorption of tetracene in the red or NIR region.…”

Biopolymer Films of Metal-Coordinated Chlorophyll-a Derivatives for “Green” Supercapacitor Electrodes

“…Connier et al reported electrogeneration and characterization of a poly(pyrrole-nickel(II) chlorin) by connecting two pyrrole units to a synthetic Ni chlorin via ester linkage, 26 while Xiong et al demonstrated electropolymerization of synthetic chlorins bearing thiophene units as reactive sites. 27 Because natural Chl-a has a vinyl group on its chlorin macrocycle, we tried to electrochemically polymerize the stable Chl-a derivatives in the initial stage of this study. A free-base chlorin, methyl pyropheophorbide-a (H 2 Chl, M = H 2 of MChl in Figure 1), 28 was attempted for electropolymerization under various conditions but no formation of polymeric films was observed.…”

“…reported electrogeneration and characterization of a poly­(pyrrole-nickel­(II) chlorin) by connecting two pyrrole units to a synthetic Ni chlorin via ester linkage, while Xiong et al . demonstrated electropolymerization of synthetic chlorins bearing thiophene units as reactive sites . Because natural Chl- a has a vinyl group on its chlorin macrocycle, we tried to electrochemically polymerize the stable Chl- a derivatives in the initial stage of this study.…”