New unsymmetrical Schiff base Ni(II) complexes as scaffolds for dendritic and amino acid superstructures

An efficient stepwise template approach has been developed that leads to a novel Ni(II) complex of an unsymmetrical 1 : 1 : 1 Schiff base derived from o-phenylenediamine, benzoylacetone and salicylic aldehyde [ abbreviated as salophbac Ni(II)]. The 3- and 5-hydroxysubstituted salicylic aldehydes lead to complexes containing reactive OH groups that were further employed as points of attachment for the ligand superstructures. A range of new O-substituted derivatives of salophbac Ni( II) complexes have been synthesized bearing N-protected (L)-amino acid moieties as well as poly(arylether) and poly(arylester) dendrons. New products have been characterized by means of H-1 and C-13 NMR, MS and IR data. The crystal structures of the 3-Boc-(L)-phenylalanyloxy, 3-Ac-(D, L)-alanyloxy and (3',5'-dibenzyloxy)-3-benzyloxy derivatives of salophbac Ni(II) complexes have been determined. The supramolecular C - H...pi, pi...pi interactions and hydrogen bonds are discussed on the basis of the crystallographic data.