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

Abstract

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).

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

“…For instance, 18 hasb een probed by 13 C-13 CE XSY by Setaka and colleagues, who found that the dynamics of the naphthalene rotor (108-10 À5 s À1 )a ppears to be much slower than the respective fluorescencetimescale. [52] In certain cases, the rotation of relatively small trigonal rotors such as tBu groups can be slowed down. Kurskii and coworkers [53] observed clearly sluggish tBu rotationi nd imeric species derived from 2,5-di-tert-butylcyclopentadienone.…”

“…Rotation of a molecular fragment inside another fragment, termed “gyrotop” (Scheme ) is very closely related to trigonal rotors. For instance, 18 has been probed by 13 C‐ 13 C EXSY by Setaka and colleagues, who found that the dynamics of the naphthalene rotor (10°–10 −5 s −1 ) appears to be much slower than the respective fluorescence timescale …”

Three-Fold Intramolecular Ring Closing Alkene Metatheses of Square Planar Complexes with cis Phosphorus Donor Ligands P(X(CH2)mCH═CH2)3 (X = −, m = 5–10; X = O, m = 3–5): Syntheses, Structures, and Thermal Properties of Macrocyclic Dibridgehead Diphosphorus Complexes

“…Such species carry primed numbers throughout this manuscript. Setaka has realized similar chemistry when the P–M–P linkages are replaced by Si–arylene–Si linkages (e.g., arylene = p -C 6 H 4 ). , …”

Bulky Selenium Ligand Stabilized Trans‐Palladium Dichloride Complexes as Catalyst for Silver‐Free Decarboxylative Coupling of Coumarin‐3‐Carboxylic Acids

“…One can make these molecules uni‐directional simply by adding dipole moment in the rotor unit [1c] . The Garcia‐Garibay [1b–f] and Setaka [1g–l] groups have independently synthesized molecular rotors having organic rotor unit and explored their rotational properties. The group of Gladysz has extensively contributed towards design and synthesis of various molecular gyroscopes having an inorganic rotor unit in the molecule and understanding their rotational behavior [1a,5] .…”