The co-planarity of the 4,4′-bipy rings can be roughly approximated where the torsion angle of C(6)–C(7)–C(8)–C(9) is 0.11 (0.55)°. The bond elongation between the C-atoms bridging the two aromatic rings of the 4,4’-bipy molecule {C(7)–C(8), 1.499(5) Å}, in comparison with those within the ring