Molecular motors with new topologies

PhD ceremony: Mr. G. Caroli, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: Molecular motors with new topologies

Promotor(s): prof. B.L. Feringa

Faculty: Mathematics and Natural Sciences

The thesis of Giuseppe Caroli is concerned with first generation molecular rotary motors. These are molecules that, under the influence of light and heat, can perform unidirectional rotation around their central double bond. Important elements in the structure are the two stereogenic centers, which dictate the direction of rotation.

Computer modeling has been performed by Caroli on the basic structure for a better understanding of the fundamental thermal isomerization processes.

He has derivatized the two stereogenic centers of the motor with long alkyl chains and with different aromatic groups, and he has studied the influence on the rotary function. The rotary function was maintained in all cases, opening more possibilities for further functionalization in the view of future applications.

Three different functionalized scaffolds have been synthetized by Caroli and used to produce structures with new topologies. In particular, three looped motors, a molecular walker, a dopant for liquid crystals, and two dimers of motors have been produced. The rotary function was found to be not largely affected by these new functionalities, except in the case of the short looped motors, where the full rotation was prevented. In these cases, the molecules behave like light driven switches. Moreover, the dimers exhibited a reduced photostationary state.

Finally, Caroli has synthetized a molecular reel, which consists of a central molecular motor, a loop and two threads. When the motor unit rotates, the threads are expected to wind around it like in a macroscopic reel. This system has only been studied to some extend, but the results are encouraging.