¹H NMR chemical shifts of BIP and BI₂P analogs in CDCl₃.

Compound	δ OH (ppm)	δ NH (ppm)a	δ NH (ppm)b
1	13.19c	—	11.48c
2	13.30c	—	11.84c
3	13.30d	—	11.87d
4	13.45e	—	11.17e
1′	13.36	12.07	11.54
2′	13.40	12.12	11.83
3′	13.42d	12.15d	11.90d
4′	13.43	12.20	∼12.20f

^aNH involved in the internal hydrogen bond between benzimidazoles (N₂H⋯N₃ in Fig. 3b).

^bNH involved in the internal hydrogen bond between the benzimidazole and the terminal proton-accepting group (either imine, such as N₄H⋯N₅ in Fig. 3b, or exocyclic amine, such as N₂H⋯N₃ in Fig. 3a).

^cData from ref. 26.

^dData from ref. 27.

^eData from ref. 22.

^fBroad signal presumably overlapped with the NH signal assigned to the internal hydrogen bond between benzimidazoles (N₂H⋯N₃ in Fig. 3b).