Recognition of histidines with a synthetic zinc amino‐oxochlorin regioisomer via synergetic coordination and hydrogen bonding

Abstract

AbstractZinc 13‐(N,N‐diethylamino)methyl‐3,3,7,8,12,17,18‐heptaethyl‐2‐oxochlorin was prepared from 2,3,7,8,12,13,17,18‐octaethylporphyrin via the regioselectively acid‐catalyzed double dehydration of cis‐12,13‐diethyl‐cis‐12,13‐dihydroxy‐2‐oxobacteriochlorin to the corresponding 12‐ethyl‐13‐vinyl‐2‐oxochlorin. The synthetic zinc amino‐oxochlorin was axially ligated with the imidazolyl group of Nα‐protected histidines in chloroform, and concomitantly the amino group of the former was hydrogen‐bonded with the carboxy group of the latter. The resulting two‐point bonding supramolecules served as models for the complexes of chlorophylls with peptides in photosynthetic apparatuses including light‐harvesting antennas and charge‐separating reaction centers. A similar 1:1 complex was produced by the interaction of the zinc amino‐chlorin with the related methionine possessing thioether and carboxylic acid moieties.