Theoretical investigation on cis-trans isomerisation of azaphosphatriptycene- based molecular gear

The cis-trans isomerization of a metal-centred molecular gear was investigated by density functional theory (DFT). The gear uses Pt(II) as stator, the azaphospha-triptycene as rotor, and the ligand introduces chlorine atoms. Under the conditions driven by light and heat, the gear can undergo switchable motion through the meshing and disengaging of two rotators. To be specific, the geometry optimization of cis-[PtCl2(Tp)(2)] and trans-[PtCl2(Tp)(2)] isomers were performed via the M06-2X functional in conjunction with def2-SVP basis set. Through rotating around the Pt-P single bond, the potential energy surface was scanned to explore the different rotational modes of the cis- and trans- isomers. In addition, time-dependent density functional theory (TD-DFT) was used to calculate molecular excitation energy and ultraviolet absorption properties. The reaction transition state of cis -> trans isomerization was calculated to study the isomerization process and the motion correlation between the two rotors during rotation.