Covalently linked dimer of chlorophyll-a derivative with an amide bond and its folded conformer

A chlorophyll-a derivative homo-dimer covalently linked with a flexible methylene-amino-methylene group at the 3-position was benzoylated to give the dyad bearing a CH2N(COPh)CH2 linker. The synthetic dyad with the relatively rigid spacer showed red-shifted visible absorption bands and was oxidized more readily, in comparison with the corresponding monomer. The optical and electrochemical properties of the dimer are ascribable to the partial pi-stacking of chlorin moieties in the benzoylated dyad, mimicking the special dimeric species in reaction centers of photochemical systems in natural phototrophs. (C) 2018 Elsevier Ltd. All rights reserved.