Supramolecular Assembly and Solution Properties of Bis(bipyridyl)ruthenium(II) Coordination Complexes of Aryl(2-pyridyl)methanones

A series of mono- and bis(2-pyridyl)-arylmethanone ligands were prepared by utilizing the reaction between either
bromobenzonitrile or dicyanobenzene and 2-lithiopyridine in either a 1:1 or a 2:1 mol ratio, respectively. They react
with [Ru(bpy)2(EtOH)2][PF6]2 to yield the new complexes [N,O-PhC(O)(2-py)Ru(bpy)2][PF6]2 (6), [p-N,O-BrC6H4C(O)(2-py)Ru(bpy)2][PF6]2 (7), [m-N,O-BrC6H4C(O)(2-py)Ru(bpy)2][PF6]2 (8), {p-[N,O-C(O)(2-py)2Ru(bpy)2]2(C6H4)}[PF6]4 (9), and {m-[N,O-C(O)(2-py)2Ru(bpy)2]2(C6H4)}[PF6]4 (10). The solid state structures of 6 and 7 show that
the octahedral cations are arranged in sinusoidal chains by π−π stacking and CH−π interactions between bipyridyl
groups. Substitution of bromine for hydrogen at the para position of the aryl group in 7 causes the aryl group to
become involved in π−π stacking interactions that organize the chains into a sheet structure. The complicated 1H
and 13C NMR spectra of the complexes have been fully assigned using 2D methods. The optical spectra show two
absorption maxima near 434 and 564 nm due to MLCT transitions. The compounds were found to be nonluminescent.
Electrochemical data acquired for CH3CN solutions of the bimetallic derivatives indicate that there is no electronic
communication between metal centers mediated either through space or through ligand orbitals. Crystallographic
information:  6·0.5CH3CN is monoclinic, C2/c, a = 24.3474(11) Å, b = 13.7721(6) Å, c = 21.3184(10) Å, β =
103.9920(10)°, Z = 8; 7 is monoclinic, P21/c, a = 10.6639(11) Å, b = 23.690(3) Å, c = 13.7634(14) Å, β =
91.440(2)°, Z = 4.