Fig. 2

Single-handed supramolecular double helix from L,L-IA and D,D-IA. a X-ray crystal structure of L,L-IA showing cis-form with β-turn at each side. Dashed green lines highlight the IHBs that form the β-turn structures β1 and β2. b Crossed double C−I···S halogen bonds between two adjacent cis-form L,L-IA molecules. Dashed black lines highlight two C−I···S halogen bonds XB1 and XB2. c 1D superstructure of cis-form L,L-IA molecules through C−I···S halogen bonding along c-axis. d Two P-helical strands in 1D superstructure of L,L-IA. e M-double and P-double helices formed, respectively, from the enantiomeric D,D-IA and L,L-IA. For clarity reasons, one side in the bilateral D,D-IA and L,L-IA molecules is depicted in blue, while the other side is depicted in red