Synthesis and hypodentate Cu(II) complexes of new tripodal tetraamine ligands incorporating a long pendant arm

Abstract

The synthesis and characterisation of the new aliphatic tripodal amine ligands apba ( N-(5-aminopentyl)- N,N-bis(2-aminoethyl)amine) and ahba ( N-(6-aminohexyl)- N,N-bis(2-aminoethyl)amine) are reported. The tetrahydrochloride salts of these ligands, as well as that of the previously reported ligand abba ( N-(4-aminobutyl)- N,N-bis(2-aminoethyl)amine), react with CuCO 3 · Cu(OH) 2 to give complexes in which the tripodal ligand coordinates to the Cu(II) ion in a hypodentate fashion, with the longest arm of the tripodal ligand remaining protonated and unbound in all cases. The crystal structure of [Cu(abbaH)Cl 2]Cl · 2H 2O · CH 3OH reveals a five-coordinate Cu(II) ion in a slightly distorted square pyramidal geometry.