RU(BPY)2(2+) AND OS(BPY)2(2+) COMPLEXES OF LARGE POLYAZA CAVITY-SHAPED LIGANDS

The Friedlander condensation of cyclic 1,2-diketones with 2-amino-5,6-dihydro-1,10-phenanthroline-3-carboxaldehyde provides a series of hexaaza cavity-shaped molecules 2a-c. Reaction with Ru(bpy)2Cl2 (where bpy = 2,2'-bipyridine) incorporates Ru(II) into a distal bidentate site. For ligands which are significantly nonplanar, a second Ru(II) or Os(II) nucleus can similarly be incorporated into the remaining distal site. The use of bpy-d8 as an auxilliary ligand simplifies the NMR spectra of the complexes and permits a detailed conformational analysis which is reinforced by an X-ray determination of the dinuclear complex [(bpy)2Ru(2c)Ru(bpy)2](PF6)4, which crystallizes in the monoclinic space group P2(1)/n with a = 13.535(6) angstrom, b = 27.399(8) angstrom, c = 22.400(8) angstrom, beta = 96.72(3)-degrees, mu = 5.39 cm-1 and Z = 4. Communication of the metal centers through the bridging ligand is examined by electronic absorption and emission spectroscopy and electrochemical analysis. Evidence is presented for limited communication between the two halves of the bridging ligand controlled by the length of the central polymethylene bridge.