ABSTRACT: Correlated rotations of triptycenes have been achieved in solution by the Iwamura-Mislow molecular bevel gears. [1] In the solid state, precise alignment and volume conservation are necessary in order to realize highly geared rotation. The pillared MOF structure synthesized and studied by Rieger (TDC-MOF-4) [2] appeared to us to have the appropriate arrangement of triptycene subunits to permit geared motion. We performed molecular dynamics (MD) simulations using the Amber force field to explore the rotational motions of triptycenes and the possibility for correlated gearing motions of multiple triptycenes in these MOFs. Umbrella sampling was used to compute the free energy landscape. MD results show that the correlated gearing rotations occur in a single zinc cluster model (Figure 1a) and between neighboring zinc clusters (Figure 1b) as well. A study of the temperature dependence of the rotational energy barrier that shows the role of entropy on rotation rates will be reported. [1] Iwamura, H. & Mislow, K. Acc. Chem. Res. 21, 175–182 (1988). [2] Vagin, S. I., Ott, A. K., Hoffmann, S. D., Lanzinger, D. & Rieger, B., Chem. Eur. J. 15, 5845–5853 (2009).

Molecular dynamics study of triptycene rotors in metal organic frameworks: Structure-enforced gearing

251st National Meeting (2016)

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