Selective formation of spiroborate-based double-stranded hetero-helicates assisted by donor–acceptor interactions

Novel ortho-linked tetraphenol strands with electron-deficient naphthalene (NDI) and perylene (PDI) diimide linkers in the middle formed double-stranded homo-helicates bridged by spiroborate groups in the presence of NaBH₄. The reaction of an electron-rich porphyrin-linked tetraphenol strand with the NDI-strand quantitatively afforded the double-stranded hetero-helicate assisted by donor–acceptor interactions between the porphyrin and NDI units with a similar molecular length to each other, while that with the longer PDI strand gave a mixture of the corresponding homo- and hetero-helicates. The two isolated homo- and hetero-helicates were successfully resolved into enantiomers by chiral HPLC.