Order–Disorder Transition of Dipolar Rotor in a Crystalline Molecular Gyrotop and Its Optical Change

Successful control of the orientation of the π-electron systems in media has been achieved in certain liquid crystals, making them applicable to devices for optical systems because of the variation in the optical properties with the orientation of the π-electron system. However, because of close packing, changing the orientation of molecules in the crystalline state is usually difficult. A macrocage molecule with a bridged thiophene rotor was synthesized as a molecular gyrotop having a dipolar rotor, given that the dipole derived from the thiophene can rotate even in the crystal. The thermally induced change in the orientation of the dipolar rotors (thiophene ring) inside the crystal, i.e., order–disorder transition, and the variation in the optical properties in the crystalline state were observed

Order–Disorder Transition of Dipolar Rotor in a Crystalline Molecular Gyrotop and Its Optical Change

Successful control of the orientation of the π-electron systems in media has been achieved in certain liquid crystals, making them applicable to devices for optical systems because of the variation in the optical properties with the orientation of the π-electron system. However, because of close packing, changing the orientation of molecules in the crystalline state is usually difficult. A macrocage molecule with a bridged thiophene rotor was synthesized as a molecular gyrotop having a dipolar rotor, given that the dipole derived from the thiophene can rotate even in the crystal. The thermally induced change in the orientation of the dipolar rotors (thiophene ring) inside the crystal, i.e., order–disorder transition, and the variation in the optical properties in the crystalline state were observed

A Molecular Balloon: Expansion of a Molecular Gyrotop Cage Due to Rotation of the Phenylene Rotor

A macrocage molecule with a bridged phenylene rotor has been reported as a molecular gyrotop, because the rotor can rotate even in a crystalline state. Although the most stable cage structure of the molecular gyrotop in a crystal was folded and shrunken at low temperature, expansion of the cage was observed at high temperature due to rapid rotation of the phenylene in a crystal. This phenomenon is analogous to the deflation and inflation of a balloon. Moreover, the unusually large thermal expansion coefficient of the crystal was estimated in the temperature range in which the expansion of the cage was observed, indicating a new function of dynamic states of the molecules

A Molecular Balloon: Expansion of a Molecular Gyrotop Cage Due to Rotation of the Phenylene Rotor

A macrocage molecule with a bridged phenylene rotor has been reported as a molecular gyrotop, because the rotor can rotate even in a crystalline state. Although the most stable cage structure of the molecular gyrotop in a crystal was folded and shrunken at low temperature, expansion of the cage was observed at high temperature due to rapid rotation of the phenylene in a crystal. This phenomenon is analogous to the deflation and inflation of a balloon. Moreover, the unusually large thermal expansion coefficient of the crystal was estimated in the temperature range in which the expansion of the cage was observed, indicating a new function of dynamic states of the molecules

Order–Disorder Transition of Dipolar Rotor in a Crystalline Molecular Gyrotop and Its Optical Change

Successful control of the orientation of the π-electron systems in media has been achieved in certain liquid crystals, making them applicable to devices for optical systems because of the variation in the optical properties with the orientation of the π-electron system. However, because of close packing, changing the orientation of molecules in the crystalline state is usually difficult. A macrocage molecule with a bridged thiophene rotor was synthesized as a molecular gyrotop having a dipolar rotor, given that the dipole derived from the thiophene can rotate even in the crystal. The thermally induced change in the orientation of the dipolar rotors (thiophene ring) inside the crystal, i.e., order–disorder transition, and the variation in the optical properties in the crystalline state were observed

Order–Disorder Transition of Dipolar Rotor in a Crystalline Molecular Gyrotop and Its Optical Change

Successful control of the orientation of the π-electron systems in media has been achieved in certain liquid crystals, making them applicable to devices for optical systems because of the variation in the optical properties with the orientation of the π-electron system. However, because of close packing, changing the orientation of molecules in the crystalline state is usually difficult. A macrocage molecule with a bridged thiophene rotor was synthesized as a molecular gyrotop having a dipolar rotor, given that the dipole derived from the thiophene can rotate even in the crystal. The thermally induced change in the orientation of the dipolar rotors (thiophene ring) inside the crystal, i.e., order–disorder transition, and the variation in the optical properties in the crystalline state were observed

Cage Size Effects on the Rotation of Molecular Gyrotops with 1,4-Naphthalenediyl Rotor in Solution

1,4-Naphthalenediyl-bridged macrocages (<b>2</b>, <b>3</b>, and <b>4</b>) were synthesized as novel molecular gyrotops. Compound <b>2</b> (C14 chains) does not show rotation of the naphthalene ring about an axis in solution. The 1,4-naphthalenediyl moieties of compounds <b>3</b> (C16 chains) and <b>4</b> (C18 chains) show restricted and rapid rotation inside the cage in solution, respectively. Therefore, steric protective effects on the rotation of the rotor in molecular gyrotops can be controlled by changing the size of the cage

Cage Size Effects on the Rotation of Molecular Gyrotops with 1,4-Naphthalenediyl Rotor in Solution

1,4-Naphthalenediyl-bridged macrocages (<b>2</b>, <b>3</b>, and <b>4</b>) were synthesized as novel molecular gyrotops. Compound <b>2</b> (C14 chains) does not show rotation of the naphthalene ring about an axis in solution. The 1,4-naphthalenediyl moieties of compounds <b>3</b> (C16 chains) and <b>4</b> (C18 chains) show restricted and rapid rotation inside the cage in solution, respectively. Therefore, steric protective effects on the rotation of the rotor in molecular gyrotops can be controlled by changing the size of the cage

1,4-Naphthalenediyl-Bridged Molecular Gyrotops: Rotation of the Rotor and Fluorescence in Solution

Macrocage molecules with a bridged π-electron system have been reported as molecular gyrotops in which the π-electron system can rotate within the cage. We recently reported the dynamics of the rotor in solution using 1,4-naphthalenediyl-bridged molecular gyrotops, which consist of cages formed of three C₁₄, C₁₆, or C₁₈ chains. In this work, we synthesized novel gyrotops with C₁₅ and C₁₇ chains and systematically investigated the activation energies for the rotation of the rotor in solution. The activation energies for rotation in solution were found to decrease with increasing size of the cage. Therefore, a rotational barrier can be designed by adjusting the length of the side chains in these molecular gyrotops. Additionally, these gyrotops were fluorescent in solution; the quantum yields and lifetimes of the fluorescence were investigated. However, these properties were not influenced by the chain length owing to a large difference in time scale between fluorescence (10^–8–10^–9 s) and the rotational dynamics inside the cage (10°–10^–5 s)

Ferrocene-diyl Bridged Macrocages: Steric Effects of the Cage on the Redox Properties of Ferrocene Moiety

The stable redox properties of ferrocene/ferrocenium have been used to investigate ferrocene-based functional materials. Herein, the steric effects of an exterior cage on the redox properties of interior metallocenes have been investigated using cyclic voltammetry measurements of ferrocene-diyl bridged macrocages and their noncage isomers. As the half-wave potential (<i>E</i>_1/2) depends on ferrocenium stabilization through solvation, positive shifts in the <i>E</i>_1/2 were observed in the macrocages. As peak separation between potentials of the anodic and cathodic peaks depends on the rate of electron transfer, marked broadening from the ideal value was observed in the macrocages due to the insulating effect of the outer cage. These steric effects of the cage on the redox properties of ferrocenes could aid the molecular design of metallocene-based functional molecules