The Pt(II)‐Azaphosphatriptycenes Gear Mechanism: Computational Insights into How Z/E Geometry Influences Rotational Behavior

The study explores how Z/E geometry of azaphosphatriptycene ( azpt ) units influences rotational behavior in Pt(II)‐azpt complexes. Using molecular dynamics (MD) (100 ns, methanol, 300–380 K), potential energy surface(PES) scans, density functional theory (DFT), quantum theory of atoms in molecules (QTAIM)/noncovalent interaction (NCI), EDA analysis, Hirshfeld mapping, and quantum descriptors, we reveal why the two isomers act as oscillating or rotating molecular gears. The Z isomer ( 1a ) exhibits torsional motion and a higher rotational barrier (∼38.1 kcal·mol −1 ). This barrier indicates the rotor is mechanically interlocked, preventing spontaneous free rotation under thermal conditions and forcing a compression of the ClPtCl angle alongside a PPtP expansion. Dense networks of CH···π, CH···ClPt, and π–π interactions stabilize conformers, preventing full rotation. In contrast, the E isomer ( 1b ) is strain‐free, stabilized only by dynamic CH···Cl contacts that break and reform, yielding low barriers (∼2.1 kcal·mol −1 ) and MD evidence of 360° rotation at elevated temperatures. Electronic differences are confirmed by HOMO–LUMO gaps, hardness/softness, and electrophilicity. Both isomers undergo photo/thermal isomerism, altering noncovalent interactions and crystal packing, where they form 1D chains. Overall, the article highlights how steric and noncovalent forces must be balanced to enable gear‐like rotation in molecular machines.