A random rotor molecule: Vibrational analysis and molecular dynamics simulations.

Molecular structures that permit intramolecular rotational motion have the potential to function as molecular rotors. We have employed density functional theory and vibrational frequency analysis to study the characteristic structure and vibrational behavior of the molecule (4('),4("")-(bicyclo[2,2,2]octane-1,4-diyldi-4,1-phenylene)-bis-2,2('):6('),2(")-terpyridine. IR active vibrational modes were found that favor intramolecular rotation. To demonstrate the rotor behavior of the isolated single molecule, ab initio molecular dynamics simulations at various temperatures were carried out. This molecular rotor is expected to be thermally triggered via excitation of specific vibrational modes, which implies randomness in its direction of rotation.