The stereoselective coordination chemistry of the helicating ligand N,N′-bis(-2,2′-dipyridyl-5-yl)carbonyl-(S/R,S/R)-1, 2-diphenylethylenediamine

Enantiomerically pure N,N′-bis(-2,2′-dipyridyl-5-yl)carbonyl- (S/R,S/R)-1,2-diphenylethylenediamine has been synthesised by linking two 2,2′-bipyridine units by (R,R)- and (S,S)-1,2-diphenylethylenediamine. The ligands possess a hindered rotation between the bipyridine chromophores, which are held together by intramolecular hydrogen bonds. ES mass spectroscopy confirmed that reaction with Fe(II), Co(III) and Cd(II) afforded dinuclear complexes. CD spectroscopy implied that enantiopure ligands conferred helicity to the metals centre giving a dominant triple helicate diastereoisomer (with the RR isomer giving a P helicate). 1H NMR spectroscopy of the cadmium complex confirmed the presence of a single diastereoisomer