Development Of Transition Metal Cluster Complexes With Macrocyclic Redox-Active Ligands Of Increasing Pocket Size
Dinuclear molecular complexes are increasingly sought in order to exploit metal-metal cooperativity to obtain new catalytic activity in a myriad of applications, including small molecule activation, organic transformations and polymerization methods. These complexes are also desirable for their potential utility in elucidating mechanistic understanding of biological systems and heterogeneous catalysis. Achieving new reactivity necessitates the synthesis of new ligands and new dinuclear molecular complexes. A series of 2,6-diiminopyridine-derived macrocyclic ligands with ring sizes of 18, 20 and 22 members have been synthesized along with the corresponding homobimetallic 3d metal complexes of Mn, Fe, Co, Ni and Cu. The solubility of these ligands and metallic complexes in aprotic organic solvents not only enables systematic characterization of the structural and physical properties with changes to both metals and macrocyclic ring sizes using techniques such as NMR spectroscopy, mass spectrometry, solution-phase UV-Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography in addition to solid state measurements using IR spectroscopy and SQUID magnetometry. The electronic understanding of both the ligand and metal complexes was further developed through computational studies.