2,6-Bis(aza­indole)pyridine: reactivity with iron(III) and copper(II) salts

1-[6-(1H-Pyrrolo[2,3-b]pyridin-1-yl)pyridin-2-yl]-1H-pyrrolo[2,3-b]pyridin-7-ium tetra­chloridoferrate(III), (C₁₉H₁₄N₅)[FeCl₄], (II), and [2,6-bis­(1H-pyrrolo[2,3-b]pyridin-1-yl-κN⁷)pyridine-κN]bis­(nitrato-κO)copper(II), [Cu(NO₃)₂(C₁₉H₁₃N₅)], (III), were prepared by self-assembly from FeCl₃·6H₂O or Cu(NO₃)₂·3H₂O and 2,6-bis­(1H-pyrrolo[2,3-b]pyridin-1-yl)­pyridine [commonly called 2,6-bis­(aza­indole)­pyridine, bap], C₁₉H₁₃N₅, (I). Compound (I) crystallizes with Z′ = 2 in the P space group, with both independent molecules adopting a trans–trans conformation. Compound (II) is a salt complex with weak C—H...Cl inter­actions giving rise to a zigzag network with π-stacking down the a axis. Complex (III) lies across a twofold rotation axis in the C2/c space group. The Cu^II center in (III) has an N₃O₂ trigonal–bipyramidal environment. The nitrate ligand coordinates in a monodentate fashion, while the bap ligand adopts a twisted tridentate binding mode. C—H...O inter­actions give rise to a ribbon motif.