Heterobimetallic M/Zn (M = Cu, Ni) complexes with open-chain N- and N,O-ligands: Template synthesis from metal powders and supramolecular crystal structures

A series of new heterometallic CuIIZnII and NiIIZnII complexes with N- and N,O open-chain multidentate ligands (L1 = 4,6,6-trimethyl-1,9-diamino-3,7-diazanon-3-ene; L2 = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane; L3 = 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetraazapentadec-6-ene and L4 = 1-hydroxy-9-oxy-4,6,6-trimethyl-3,7-diazanon-3-ene) have been prepared through the “direct template synthesis” approach, which is a combination of classical template reactions of amines with acetone/formaldehyde and the “direct synthesis” method based on using elemental metals as starting materials. There is a significant decrease in the reaction time when the “direct synthesis” method is used compared to the conventional template condensation methods. X-ray crystallographic analyses of the complexes with the general formula M(L)ZnX4 and [CuL4ZnCl3]2 (M = Cu2+, Ni2+; L = L1-L3; X = Cl−, NCS−) reveal the presence of long intermolecular distance interactions, such as semi-coordination, S⋯S and H-bonding, in their crystal organization.