Feb 18, 2021
Research image
A highly-collaborative study at UCLA by García-Garibay, Houk and Brown (Physics) groups show promising applications of dipolar rotors in the solid state.              
The team's research is a key step to the development of emergent dipolar arrays and other types of crystalline molecular machines. Their paper titled “Dipolar Order in an Amphidynamic Crystalline Metal–organic Framework Through Reorienting Linkers” was published in the February 15, 2021 issue of Nature Chemistry.
Co-authors from the Department of Chemistry & Biochemistry are graduate student Ieva Liepuoniute, former postdoc Dr. Salvador Pérez-Estrada, graduate student Trevor Chang, and Professor Ken Houk and Professor Miguel García-GaribayTheir co-authors are Professor Stuart Brown and members of his group in the UCLA Department of Physics and Astronomy.
The Chem & Biochem research team
Ieva Liepuoniute, Dr. Salvador Pérez-Estrada, Trevor Chang, Professors Miguel García-Garibay and Ken Houk.
Spontaneous Collective Alignment of Reorienting Dipolar Arrays
By Ieva Liepuoniute (Chemistry Graduate Student, García-Garibay and Houk groups)
The development of crystalline materials with engineered rotational motion has been a topic of recent interest among physicists, chemist and materials scientists. To this end, the Garcia-Garibay group proposed a novel class of materials, called amphidynamic crystals, that contain moving elements - a rotator, bound to a static framework. One of the major pursuits was to install functional handles, such as permanent electric dipoles, onto rotator units and to use them to induce new and tunable material properties. The researchers hypothesized that such individual rotary components, if harnessed collectively, will lead to emergent behavior in the form of spontaneous collective alignment as the freely reorienting dipole arrays reach their collective ground state configurations. This study describes the culmination of efforts towards the development of the first example of such a system. The researchers were able to develop structural solutions for crystals with dipoles that have intrinsic rotational barriers on the order of magnitude of thermal energies at room temperature allowing them to interact with each other to generate spontaneous order.
The scientific curiosity to characterize this ultrafast amphidynamic system with an emergent spontaneous order led to a highly interdisciplinary approach: building a dielectric spectroscopy instrument to get insight into material polarization, running extensive density function theory (DFT) calculations to characterize coupled-motion dynamics, performing solid state NMR measurements to confirm ultrafast rotation, and running Monte-Carlo simulations to reveal the effects of dipole-lattice and dipole-dipole interactions.
Looking ahead, crystals of dipolar molecular rotors provide one of the most promising platforms for the development of intelligent materials and artificial molecular machines. 
Read more about the research on Ieva Liepuoniute’s “Behind the Paper” blog post on the Nature Chemistry website.
Penny Jennings, UCLA Department of Chemistry & Biochemistry, penny@chem.ucla.edu.