Transition metal complexes of 2,2'-bipyridine

Unlike the structures of pyridine complexes, the two rings in bipy are coplanar, which facilitates electron delocalization.

As a consequence of this delocalization, bipy complexes often exhibit distinctive optical and redox properties.

Almost always, it is a bidentate ligand, binding metal centers with the two nitrogen atoms.

Examples: Bipyridine complexes absorb intensely in the visible part of the spectrum.

With respective pKa's of 4.86 and 4.3 for their conjugate acids, phenanthroline and bipy are of comparable basicity.