High yield preparation of a novel tetrakis[ruthenium tris(bipyridine)]calix[6]arene derivative with good diastereomeric purity

In order to develop methodology for the selective preparation of complex molecular structures with potential photochemical or electron transfer functions, the diastereoselective synthesis of multiple ruthenium tris(bipyridine) complexes tethered to a central calix[6]arene core was investigated. Applying recently developed methodology, the resolved precursor cis-Delta-[Ru(bpy)(2)(DMSO)Cl]PF6 (98.6% ee) was efficiently reacted with a novel calix[6]arene derivative, to give the tetrakis[Ru(bpy)(2)(bpy')]calix[6]arene derivative (9) with almost complete retention of absolute stereochemistry at each of the four metal centres, as seen by the unusually strong molar circular dichroism (CD) spectrum. The synthesis of racemic 9 was also carried out, and demonstrated to have an inactive CD spectrum. (C) 1998 Elsevier Science Ltd. All rights reserved.