A Prospective Ultrafast Hemithioindigo Molecular Motor

Abstract

The maximum speed of light‐driven molecular motors is an important key‐property governing not only their overall performances but also many advanced functions. Currently, special emphasis lies on increasing the rate of unidirectional rotations to surpass natural systems and harness the full potential of artificial motors. Herein, we report a new molecular setup for a prospective light‐powered three‐step motor based on the hemithioindigo chromophore. Comprehensive quantum chemical treatment predicts a very low energy barrier for the only thermal ratcheting step in the unidirectional 360° rotation. Thus an ultrafast motion in the THz range could be possible with this motor at high light intensities and consequently a precise control of rotation speeds solely by light intensity variations could potentially be achieved. Experimental analyses using X‐ray crystallography and solution spectroscopy deliver first insights into the working mechanism and show that visible‐light photoswitching is feasible in both stable switching states. Additionally, significant alterations of the ground‐state energies can be induced by pH changes without hampering photoswitching capabilities.

Molecular photoswitches in aqueous environments

“…264 Moreover, HTIs were used to build more machine-like systems with several HTI units to generate complex motion, 265,266 in information processing, 267 or to function as photoresponsive receptors. 268,269 The scaffold was further functionalized to construct unidirectional molecular motors, [270][271][272][273][274][275][276] which behaviour is highly solvent-dependent 249 and influenced by the presence of water. 277 Aurones (Fig.…”

Effect of charge-transfer enhancement on the efficiency and rotary mechanism of an oxindole-based molecular motor

“…The rst molecular-level step in vision 1 represents a reference model for the design of functional photo-activated molecules [2][3][4][5][6][7][8][9][10][11][12][13][14] oen called photoactuators: this is the photochemical doublebond isomerisation of the protonated Schiff base of 11-cisretinal (rPSB, see Fig. 1A), the co-factor of the scotopic visual pigment Rhodopsin (Rho).…”

Steric Effects on the Thermal Processes of Hemithioindigo Based Molecular Motor Rotation

“…Three different types of molecular motors have been developed by our group so far using hemithioindigo (HTI) [2j,10b,11] as structural platform. The first type operates similar to the classical Feringa motor in four different steps in which two photoisomerization reactions are intersected by thermal helix inversion steps [2e–g,i,4a] . The second type of motor operates in three steps each of which is light driven and thus thermal ratcheting steps are omitted [2h] .…”

“…The first type operates similar to the classical Feringa motor in four different steps in which two photoisomerization reactions are intersected by thermal helix inversion steps. [ 2e , 2f , 2g , 2i , 4a ] The second type of motor operates in three steps each of which is light driven and thus thermal ratcheting steps are omitted. [2h] The third type allows a more complex directional motion to be realized where a figure eight shape is followed in four distinct steps.…”