Zinkkomplexe von Aminosäuren und Peptiden, 2[1]. Koordination einfacher Histidin‐Derivate an Zink

Abstract

Zinc Complexes of Amino Acids and Peptides, 2[1]. – Coordination of Simple Histidine Derivatives to ZincThe bis(L‐histidine)ZnCl2 complex 1 is likely to have tetrahedral ZnN2Cl2 coordination. For the compound (L‐histidine)‐ZnCl2 · HCl (2) a structure determination has revealed a tetrahedral ZnOCl3 coordination. Of the C‐protected histidine derivatives His‐OMe and His‐NH2 and zinc salts of non‐coordinating anions the complexes (His‐OMe)2ZnX2 (3) and (His‐NH2)2Zn(ClO4)2 (4) were obtained. A structure determination of (His‐OMe)2Zn(BPh4)2 · H2O has revealed a ZnN4 coordination with chelating histidine units. Of the N‐protected histidine derivative Nα‐acetylhistidine the complexes (Ac‐His)ZnX · H2O (5, X = ClO4, BF4) have been isolated which are coordination polymers in the solid state. From pH‐dependent 13C‐NMR studies it is concluced that in solution the imidazole N and carboxyl O are coordinated to zinc in (Ac‐His)Zn and (Ac‐His)2Zn units. The doubly protected histidine derivative Bz‐His‐OMe acts as a monodentate ligand forming the tetrahedral complexes (Bz‐His‐OMe)4Zn(ClO4)2 (6) and [(Bz‐His‐OMe)2Zn(2,9‐dimethyl‐o‐phenanthroline)](ClO4)2 (7).