π-Dimer formation as the driving force for calix[4]arene-based molecular actuators

ORGN 433

Changsik Song, cssong@mit.edu and Timothy M. Swager, tswager@MIT.EDU. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
We have designed a molecular actuator (1) which consists of calix[4]arenes as a molecular hinge and oligothiophenes as a electroactive unit. The proposed driving force for its dimensional change is a π-dimer formation between oxidized olighthiophenes. This mechanism (what we would refer to as a “molecular mechanism”) is a sharp contrast to the conventional “swelling mechanism”, in which a volume change of bulk materials is caused by uptake or release of counter-ions and accompanied solvent molecules upon oxidation or reduction, as polypyrrole actuators operate. The molecular mechanism utilizes a conformational displacement of a single strand of the polymer. Here we confirm by the model compound study that π-dimer formation indeed can be a driving force. As the model, two oligothiophene moieties were connected by a calix[4]arene hinge. When oxidized in dichloromethane at room temperature, it formed a π-dimer, which was evident in UV-vis spectroscopy, EPR, and cyclic voltammetry.