Encapsulating propeller-like columnar liquid crystals with an aromatic outer shell: influence of phenoxy-terminated side chains on the phase behaviour of triphenylbenzenes

Tailoring of phase transition temperatures of columnar liquid crystals by side chain variation is often associated with an undesired change in the mesophase type and/or geometry. To overcome this problem phenoxy-terminated side chains rather than alkyl side chains were grafted onto triphenylbenzenes, which resulted in reduced clearing points, while melting points were little affected. More importantly, helical columnar self-assembly was not compromised.

Formation of Zwitterionic Fullerodendron Using a New DBN-Focal Dendron

A new poly(amidoamine) dendron having 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) at the focal point was synthesized. Interestingly, formation of zwitterionic fullerodendrons (λ_max = 930 nm for C₆₀ and 795 nm for C₇₀) were observed by Vis-NIR spectroscopy upon the reaction of C₆₀ or C₇₀ with the DBN-focal dendron. In particular, the C₇₀ anion was effectively stabilized by the site isolation effect of the dendritic wedge. The half-life of fullerodendron 12b having C₇₀ anion at the focal point reaches 7,345 min, which is 20 times longer than that of complex between C₆₀ and pristine DBN. Furthermore, in order to confirm the structure of the zwitterionic complex, fullerodendron 12a was reprecipitated from benzonitrile/1,2,4-trimethylbenzene, and was observed using IR spectroscopy and APPI-MS.

High-resolution characterization of liquid-crystalline [60]fullerenes using solid-state nuclear magnetic resonance spectroscopy

Liquid-crystalline materials containing fullerenes are valuable in the development of supramolecular switches and in solar cell technology. In this study, we characterize the liquid-crystalline and dynamic properties of fullerene-containing thermotropic compounds using solid-state natural abundance (13)C NMR experiments under stationary and magic angle spinning sample conditions. Chemical shifts spectra were measured in isotropic, liquid-crystalline nematic and smectic A and crystalline phases using one-dimensional (13)C experiments, while two-dimensional separated local-field experiments were used to measure the (1)H- (13)C dipolar couplings in mesophases. Chemical shift and dipolar coupling parameters were used to characterize the structure and dynamics of the liquid-crystalline dyads. NMR data of fullerene-containing thermotropic liquid crystals are compared to that of basic mesogenic unit and mesomorphic promoter compounds. Our NMR results suggest that the fullerene-ferrocene dyads form highly dynamic liquid-crystalline phases in which molecules rotate fast around the symmetry axis on the characteristic NMR time scale of approximately 10 (-4) s.