FIRST-GENERATION CHIRAL METALLODENDRIMERS - STEREOSELECTIVE SYNTHESISOF RIGID D-3-SYMMETRICAL TETRANUCLEAR RUTHENIUM COMPLEXES

Condensation reactions between the enantiopure, substitutionally inert building blocks Delta-[Ru(1,10-phenanthroline- 5,6-dione)(3)][PF6](2) (2) and phen)(2)(1,10-phenanthroline-5,6-diamine)][PF6](2) (3) gave t he D-3-symmetric tetramer [(Delta-(phen)(2)Ru(tpphz))(3)-Delta-Ru](8+) (Delta Delta(3-)1) in 68% isolated yield as the PF6- salt (where tpph z is tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2 '',3 ''-j]phenazine). Rea ctions between appropriate enantiomers of 2 and 3 also yielded the rem aining D-3 isomers Lambda Delta(3)-1, Delta Lambda(3)-1, and Lambda La mbda(3)-1 which collectively represent the highest nuclearity Ru oligo mers based on bidentate type ligands prepared in a stereospecific fash ion to give diasteromerically and enantiomerically pure products. The complexes were purified via cation-exchange HPLC. H-1 and C-13 NMR, CO SY and HMQC NMR, and W-visible spectroscopy were employed to character ize these supramolecular assemblies. MALDI-TOF mass spectrometry gave parent molecular ion peaks corresponding to the species m/z 2638 [1 - 8PF(6)](+), 2783 [1 - 7PF(6)](+), 2928 [1 - 6PF(6)](+), 3073 [1 - 5PF( 6)](+), 3218 [1 - 4PF(6)](+), and 3363 [M - 3PF(6)](+), proving the ma cromolecular structure. Circular dichroism spectroscopy was used to de termine the absolute stereochemistry and optical purity of each of the se stereoisomers.