Unexpected helicity control and helix inversion: homochiral helical nanotubes consisting of an achiral ligand.

The ligand tppda has been designed and synthesized as molecular leverage for helicity control when reacted with Cd(2+) ions. The guests MeOH or DMF preferentially stabilize the P-helical isomer, while the guest H2O causes a helix inversion to give the M-helical isomer as the major isomer without any chiral auxiliary.