Minimalist End Groups for Control of Absolute Helicity in Salen- and Salophen-Based Metallofoldamers

(S)-1-Methylindan end groups are effective controllers of absolute helicity in Ni-salen- and Ni-salophen-based foldamers derived from (R,R)-trans-1,2-cyclohexanediamine and 1,2-phenylenediamine, respectively. Evidence for the helicity of the described complexes was provided through X-ray crystallography and study of chiroptical properties in solution. The chiral end groups control the absolute sense of helicity for the salen complexes, even in a case where the helical bias of the end group is mismatched relative to that of the internal diamine.