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 1H and 13C 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⋯π, π⋯π interactions and hydrogen bonds are discussed on the basis of the crystallographic data.