Journal of Physical Chemistry A, Vol.107, No.8, 1207-1215, 2003
Modeling of a rotaxane-based molecular device
A computational procedure is presented for investigating photoinduced switchable rotaxanes and demonstrated for a known system. This procedure starts with the generation of > 10(4) chemically reasonable rotaxane coconformations based on an empirical intramolecular potential-energy function. Each of the structures is then assigned by its gross structural features (coiled or extended) and by the position of the ring along the shaft. Single-point energy calculations at the semiempirical (AM I) level are then carried out for each structure in the singlet (ground), triplet, and anionic doublet states. The structural features are then correlated with energy for each state. What emerges is a profile of the structure-energy relationship that captures the salient features of the system that endow it with devicelike character. The full geometry optimization of a subset of the coconformations demonstrates that the procedure based on single-point calculations is sufficient to obtain a profile of the relationship of the structural features to energy that is consistent with experiments at a greatly reduced computational cost.