Crystal structure of bromo(2,2':6',2"-terpyridine)(2-(phenylazo)-pyridine)ruthenium(II) tetrafluoroborate.

The title compound, C26H20N6BrRu(BF4), crystallizes in the centrosymmetric space group P2(1)/n and consists of discrete complex units. The Ru(II) ion is octahedrally coordinated to one 2,2':6',2"-terpyridine (tpy), one 2-(phenylazo)pyridine (azpy) and a Br atom in trans-axial position at a distance of 2.547(5)A. The shorter Ru-N (azo) distance (1.960(3)A) than the Ru-N(py) distance (2.061(3)A) signifies a strong pi-backbonding, which leads to a longer, N=N (azo) bond (1.304(4)A).