Thermosalient Amphidynamic Molecular Machines: Motion at the Molecular and Macroscopic Scales

The supramolecular amphidynamic rotor 1, composed of two carbazole molecules acting as the stator and a DABCO rotator, exhibits remarkable thermosahence above 316 K. During this process, the crystals spontaneously transduce collective molecular displacements into macroscopic movement due to a phase transition, which is described by single-crystal X-ray analyses from 100 K to 320 K. The fast rotation in the low-temperature phase (I) occurs with a low activation energy E-a(I) approximate to 2.6 kcal mol(-1) and a pre-exponential factor A(I) approximate to 10(12) s(-1). Increased symmetry of the cavity in the high-temperature phase (II) resulted in slower dynamics, regardless of a smaller rotational barrier, E-a(II) 0.5 kcal mol(-1), due to the large reduction in the pre-exponential factor to A(II) approximate to 10(7) s(-1). These results demonstrate that a relatively small distortion of lattice framework leads to drastic dynamic effects at both molecular and macroscopic scales, helping us to understand responsive crystalline materials.