Hydrostatic Pressure on Toroidal Interaction and Propeller Chirality of Hexaarylbenzenes: Explicit Solvent Effects on Differential Volumes in Methylcyclohexane and Hexane

Abstract

A unique and effective interaction between the peripheral aromatic blades makes hexaarylbenzenes (HABs) attractive in fundamental research as well as for various applications such as molecular wires, sensors, and supramolecular assemblies. The chiroptical responses of HABs are susceptible to environmental factors such as solvent and temperature owing to the dynamic conformational transitions between the conformers. In this study, pressure dependence on the propeller chiral HABs in two different solvents was studied in detail. The effective differential volumes for two different equilibria were determined by quantitative analyses of CD spectra, affording very large differential volumes from the propeller to toroidal conformer (ΔVT‐C) of +43 and +42 cm3 mol−1, for H2 and H6, respectively, in methylcyclohexane. The value of H6 was further enhanced to +72 cm3 mol−1 in hexane, the largest value for the typical unimolecular conformational change. Such a response of propeller chirality in HABs is expedient in designing more advanced piezo‐sensitive materials.

Diastereoselective Photocycloaddition Reaction of Vinyl Ether Tethered to 1,4‐Naphthoquinone

“…Along with the determination of the absolute configuration, chiroptical methods, combined with theoretical investigation, becomes a versatile tool to investigate the conformational behavior of chiral molecule in condensed phase ,. Among these, the circular dichroism (CD) spectra are one of the profound and most used method for this purpose ,,,,. Figure shows the experimental CD spectra of ( R )‐ 1 in methylcyclohexane at 25 °C, together with theoretically predicted CD spectra for pro‐( R 3 ) and pro‐( S 3 ) conformers of ( R )‐ 1 .…”

“…[35,36] Among these, the circular dichroism (CD) spectra are one of the profound and most used method for this purpose. [37,38,39,40,41] Figure 5 shows the experimental CD spectra of (R)-1 in methylcyclohexane at 25°C, together with theoretically predicted CD spectra for pro-(R 3 ) and pro-(S 3 ) conformers of (R)-1. As the theoretical spectra were nearly mirror-imaged to each other, the observed experimental spectrum can be understood as the pro-(R 3 ) and pro-(S 3 ) conformers are in equilibrium and the latter is slightly preferred under the condition.…”

Does Pressure Break Mirror‐Image Symmetry? A Perspective and New Insights

“…[29][30][31] On increasing pressures, a varied polymorphism can be detected, some structures exhibiting large differential volumes and/or undergoing symmetry variations in the unit cell. [32,33] Thus, for L-threonine, three transitions have been observed, the first two retaining the P2 1 2 1 2 1 symmetry and dropping to P2 1 above 14 GPa. [34] Enantiomeric L,L-lactide, whose polymerization affords stereoregular poly(lactic) acid, undergoes spontaneous polymerization to the amorphous polymer by increasing the temperature at pressures greater than 0.1 GPa.…”

“…Note this expression (33) reduces to the conventional one due to racemization in the limit as Q LD ! 0, that is, either for vanishing excess molar volume, and or as the pressure p approaches p 0 .…”

Hydrostatic‐Pressure‐Controlled Molecular Recognition: A Steroid Sensing Case Using Modified Cyclodextrin

“…The effects on homogeneous solutions upon hydrostatic pressurization are presented herein, rather than the solid‐state chemistry under high pressure using diamond anvil cells [57,58] . Specifically, we have so far demonstrated that emission behavior of the mechanochromic luminogens [59,60] and the chromophoric polymers, [61,62] solvatochromism of the Reichardt's dye, [63] and chiroptical properties of the hexaarylbenzenes [64] are critically regulated by hydrostatic pressure. Therefore, these research trends prompted us to construct a novel pressure‐controlled molecular recognition system.…”