Double helix-to-double helix transformation, using platinum(II) acetylide complexes as surrogate linkers

We describe novel optically active double helices consisting of complementary strands stabilized by amidinium-carboxylate salt bridges. The m-terphenyl groups of each strand are joined by trans-Pt(II) acetylide complexes with pendant PPh3 ligands as the surrogate linker, which converts to cis counterparts by a ligand exchange reaction with cis-1,2-bis(diphenylphosphino)ethylene, resulting in the formation of double helices with different structures. Subsequent iodine-promoted reductive elimination on the Pt(II) atoms generates the fully organic, enantiomerically pure double helices.