Photoinduced dynamics in hydrogen-bonded rotaxanes

Abstract

Two classes of rotaxanes are described in which photoinduced processes modulate a large-amplitude motion. In the first type, E-Z-isomerization of a fumaric diamide unit to a maleic diamide leads to a substantial weakening of the hydrogen bonds between the diamide and the macrocyclic ring that surrounds it. As a result, the rate of the pirouetting motion is increased approximately by six orders of magnitude. In the second type, intermolecular photoinduced electron transfer is used to induce a reversible shuttling motion on a time scale of microseconds. Medium effects on the rate of shuttling are presented.

Excited state distortions in a charge transfer state of a donor–acceptor [2]rotaxane

“…A [2]rotaxane is a mechanically interlocked molecule that has one ring component and one dumbbell-like component, consisting of two large stoppers attached to a rod that prevents the ring from slipping off. [1][2][3][4][5][6] A [2]pseudorotaxane is identical except that it has no stoppers on the rod to hold the ring in place. Pi stacking between the ring and portions of the rod can help to hold the ring in place around the rod.…”

Hydrogen-Bond-Mediated Template Synthesis of Rotaxanes, Catenanes, and Knotanes

“…Most work was, however, devoted to the generation of light-driven shuttles [205][206][207][208], one example of which is presented in Fig. 24 [209].…”

Photo-driven molecular devices

“…The intrinsic random motions of molecular machines make the detection of the stimuli-induced, relative movements of their components a nontrivial phenomenon, as compared to the easily detectable, obvious motions executed by macroscopic machines. Three types of external stimuli-that is chemical, [38][39][40][41][42][43][44][45] electrochemical, [46][47][48][49][50][51][52][53][54] and photochemical [54][55][56][57][58][59][60][61][62][63][64] -have been employed to induce well-defined mechanical movements within molecular machines. Several spectroscopic and electrochemical techniques have been introduced to distinguish the stimuli-induced nanomechanical motions from the random Brownian ones.…”