Metal directed self-assembly of Tetranuclear Cu II and Ni II clusters

The self-assembly of two pyridine hydrazone based tritopic ligands appended with terminal carboxylate groups with CuII and NiII have been investigated. These polytopic ligands with tridentate coordination pockets were designed to produce homoleptic [3×3] grid complexes on reaction with transition metals. Despite the formation of anticipated metallogrids as the final self-assembly outcome, metal ion geometric preferences and ligand flexibility lead to the formation of tetranuclear clusters in the self-assembly process with CuII and NiII metal ions. These results illustrate the dynamic nature of the metal–ligand interactions and flexible nature of the ligand backbone in coordination self-assembly. The synthesis, structure and magnetic properties of three tetraanuclear species {[Cu4(H2L1b)2(OTf)4(OH)2(H2O)2]·6H2O}n (1), [Ni4(L2a)2(OCH3)4]·4H2O (2), [Cu4(L2b)2(OTf)4(H2O)4]·6H2O (3) involving two tritopic ligands with central pyridine framework are described.GRAPHICAL ABSTRACT Synopsis: Metal Directed Self-Assembly of Tetra Nuclear CuII and NiII Clusters Avinash Lakma, Sayed Muktar Hossain, Rabindranath Pradhan and Akhilesh Kumar Singh ...xxxx-xxxx Three tetranuclear non-grid complexes have been synthesized by reacting two pyridine hydrazone-based tritopic ligands with CuII and NiII salts. All complexes are spectroscopically and structurally characterized and their magnetic properties have been studied.