Enhancement of the helical twisting power of a ruthenium complex by the introduction of an achiral bulky unit

ABSTRACT

Helical twisting powers of a series of ruthenium complexes with screw-like Δ, Λ chirality were investigated in N-(4-Methoxybenzylidene)-4-butylaniline (MBBA). Λ-[Ru(acac)₂(trop)] (acac = acetylacetonate, trop = tropolonate) shows a fairly low HTP of 18 µm⁻¹, while we found that the HTP increased almost double by connecting with an achiral bulky unit [Ru(Cp)(dppe)] (Cp = cyclopentadienyl, dppe = 1,2-bis(diphenyl)phosphinoethane) that was found to behave as a molecular “picket fence” to force the orientation of surrounding MBBA molecules.

KEYWORDS:

• Chiral dopant
• Cholesteric
• metal complex Δ
• Λ chirality
• molecular picket-fence

Funding

This work was financially supported by Kitasato University Research Grant for Young Researchers, Futaba Denshi Foundation, and JSPS KAKENHI, Grant-in-Aid for Young Scientists (B), Grant Number 16K21353.