We demonstrate the synthesis and characterization of regioisomeric late transition metal‐aluminum heterobimetallic complexes containing 3‐ and 4‐oxypyridine ligands which bridge between the aluminum and transition metal center (Rh or Ir). Combined experimental and theoretical data allow for direct comparison of the electronic effect of the two different aluminum‐containing ligands on the late transition metal center. In combination with electronic data regarding previously reported 2‐oxypyridine bridged systems, we report a measurable decrease in ligand donor power as the regiosubstitution of the oxypyridine bridge is varied from 2‐ to 4‐ to 3‐. In all cases, addition of aluminum is found have a minimal effect on the donor ability of the oxypyridine bridge in dichloromethane solution.

A series of seven molybdenum(III) complexes with the general formula of [Mo(diimine)Cl 4 ] − were synthesized and characterized by X-ray diffraction, IR, cyclic voltammetry (CV), and UV−vis. The complexes were discovered to be highly solvatochromic, showing shifts in λ max between ∼120 and 170 nm in solvents ranging from water to acetone. Varying the substituents on the diimine ligand influenced the absorption energy such that electron-withdrawing groups induced a red shift while electron-donating groups exhibited the opposite effect. The complexes were surprisingly stable in both acidic and basic solutions, and in the case where carboxylic acid substituents were present, additional shifts in the absorption maxima were observed, corresponding to the state of protonation of these groups. Both the Mo IV/III and Mo III/II redox couples were observed in CV experiments and were complemented with density functional theory (DFT) calculations.