Single-Crystal Optical Actuation Generated by 100% SO2 Linkage Photoisomerization in a Ruthenium-Based Coordination Complex

Single-crystal optical actuators are emerging as a new field of materials chemistry because of their wide-ranging potential applications, from light-induced molecular motors to photosensing technologies. Ruthenium-based coordination complexes that contain sulfur dioxide linkage photoisomers have shown particular promise as optical actuators, given that they may exhibit either optical switching or nano-optomechanical transduction in their single-crystal form. The type of single-crystal optical actuation observed in a specific compound within this family of complexes depends upon the nature of the ligand that lies trans to this SO2 linkage photoisomer, since this governs the type and extent of photoisomer (eta(2)-(OS)O or eta(1)-OSO) that will form upon the application of light. We report the discovery of a new complex, trans-[Ru(SO2)(NH3)(4)(3-iodopyridine)]tosylate(2) (1), which forms an eta(1)-OSO photoisomer with 100% photoconversion upon the application of 505 nm light. The photoisomerization process in the ruthenium-based cation of 1 stimulates rotation and translation of the toluenic constituent of its neighboring anion, thereby affording nano-optomechnical transduction. We show that this eta(1)-OSO photoisomer transitions to its more thermally stable eta(2)-(OS)O photoisomer with an activation energy, E-a, of 11(2) kJ/mol using thermally activated single-crystal optical absorption spectroscopy. The application of external light with different wavelengths to 1 is also shown to cause a variation in its optical absorption spectral characteristics. This suggests that the photophysical properties of 1 may be tunable with light.

Automated summary

Single-crystal optical actuators are a new field of materials chemistry with wide-ranging potential applications, from light-induced molecular motors to photosensing technologies. The type of single-crystal optical actuation observed in a specific compound within this family of complexes depends upon the nature of the ligand that lies trans to the SO2 linkage photoisomer.