Polyaza cavity-shaped molecules. 12. Ruthenium(II) complexes of 3,3'-annelated 2,2'-bipyridine: synthesis, properties, and structure

Ruthenium(II) complexes of the types RuL/sub 3/(PF/sub 6/)/sub 2/ and Ru(bpy)/sub 2/L(PF/sub 6/)/sub 2/ have been prepared where bpy = 2,2'-bipyridine and L is a 3,3'-polymethylene-bridged derivative of 2,2'-bipyridine. Analysis of the NMR chemical shifts of H/sub 4/, H/sub 5/, and H/sub 6/ provides insight into the conformation of the complex as well as the strength of the coordinative bond. The absorption and emission energies of these complexes are quite similar to those of Ru(bpy)/sub 3//sup 2 +/, while the emission intensities for complexes with highly distorted ligands are diminished. The oxidation potentials of the tris complexes, RuL/sub 3/(PF/sub 6/)/sub 2/, shift to more negative potential with increasing length of the polymethylene bridge. An X-ray structure has been determined for the complex Ru(bpy)/sub 2/(4d)(PF/sub 6/)/sub 2/ with the molecular formula C/sub 34/H/sub 32/F/sub 12/N/sub 6/OP/sub 2/Ru, which crystallizes in the space group P1 with two molecules per unit cell and a = 12.485 (3) A, b = 12.492 (7) A, c = 12.563 (3) A, ..cap alpha.. = 96.91 (3), ..beta.. = 109.80 (2)/sup 0/, and ..gamma.. = 90.44 (3)/sup 0/. Of the two diastereomers possible for the complex, only one is detected, indicating that the ..delta.. form of the metal preferentially coordinates with the D form of 4d (4d = 3,3'-tetramethylene-2,2'-bipyridine) and the Lambda form of the metal coordinates with the L form of 4d. Substantial nonplanarity of the pyridine rings is observed.