Abstract
Novel double helices covalently bridged by cyclic boronate esters were synthesized from complementary dimers with an m-terphenyl backbone joined by a chiral or achiral phenylene linker bearing diethyl boronates and diols, respectively. The X-ray crystallographic analysis and variable-temperature NMR and circular dichroism measurements, along with theoretical calculations, revealed that the double helices function as a “molecular rotor” in which the cyclic boronate ester units rotate, yielding two stable rotamers at low temperatures. Moreover, our data indicates that the covalently bonded double helices can undergo a unique helix-inversion simultaneously with a rotational motion of the boronate esters.
Original language | English |
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Pages (from-to) | 927-935 |
Number of pages | 9 |
Journal | Chemistry - An Asian Journal |
Volume | 12 |
Issue number | 8 |
DOIs | |
State | Published - Apr 18 2017 |
Externally published | Yes |
Funding
This work was supported in part by a Grant-in-Aid for Scientific Research (S) (no. 25220804 to E.Y.) and a Grant-in-Aid for Young Scientists (B) (no. 26810068 to H.I.) from the Japan Society for the Promotion of Science (JSPS). The authors thank Prof. Takahisa Ikeue of Shimane University for his valuable advice for the line-shape simulation of the variable-temperature NMR spectra of the double helices.
Keywords
- chirality
- double helix
- helical structures
- helix inversion
- molecular rotors