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

The Friedlander condensation of cyclic 1,2-diketones with o-5,6-dihydr o-1,10-phenanthroline-3-carboxaldehyde provides a series of hexaaza ca vity-shaped molecules 2a-c. Reaction with Ru(bpy)2Cl2 (where bpy = 2,2 '-bipyridine) incorporates Ru(II) into a distal bidentate site. For li gands which are significantly nonplanar, a second Ru(II) or Os(II) nuc leus can similarly be incorporated into the remaining distal site. The use of bpy-d8 as an auxilliary ligand simplifies the NMR spectra of t he complexes and permits a detailed conformational analysis which is r einforced 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 = 22.40 0(8) angstrom, beta = 96.72(3)-degrees, mu = 5.39 cm-1 and Z = 4. Comm unication of the metal centers through the bridging ligand is examined by electronic absorption and emission spectroscopy and electrochemica l analysis. Evidence is presented for limited communication between th e two halves of the bridging ligand controlled by the length of the ce ntral polymethylene bridge.