Nanooptomechanical Transduction in a Single Crystal with 100% Photoconversion

Abstract

Materials that exhibit nanooptomechanical transduction in their single-crystal form have prospective use in light-driven molecular machinery, nanotechnology, and quantum computing. Linkage photoisomerization is typically the source of such transduction in coordination complexes, although the isomers tend to undergo only partial photoconversion. We present a nanooptomechanical transducer, trans -[Ru(SO 2 )(NH 3 ) 4 (3-bromopyridine)]tosylate 2 , whose S-bound η 1 -SO 2 isomer fully converts into an O-bound η 1 -OSO photoisomer that is metastable while kept at 100 K. Its 100% photoconversion is confirmed structurally via photocrystallography, while single-crystal optical absorption and Raman spectroscopies reveal its metal-to-ligand charge-transfer and temperature-dependent characteristics. This perfect optical switching affords the material good prospects for nanooptomechanical transduction with single-photon control.

Structural Capture of η1-OSO to η2-(OS)O Coordination Isomerism in a New Ruthenium-Based SO2-Linkage Photoisomer That Exhibits Single-Crystal Optical Actuation

“…Indeed, this thermal reverse-isomerization process is deemed to operate in a thermodynamic fashion in [RuSO 2 ] complexes once these crystals lie above their metastable temperature. 38 − 40 , 43 − 46 Therefore, if one elevates a crystal of 1 to a temperature that is even closer to, but just above, its metastable temperature, one can monitor its thermal reverse-isomerization process over a much longer timeframe.…”

“…Thereby, three peaks are significant at 90 K: the largest peak at 340 cm –1 , which represents a Ru–OSO vibrational stretch; 44 the more modest peak at 540 cm –1 , which is indicative of an SO 2 deformation mode of the η 1 -OSO isomer; 44 , 53 and the weakest peak at 1130 cm –1 , which is reminiscent of an η 1 -SO 2 symmetric stretching mode. 43 , 44 , 53 …”

“…As the temperature of the crystal of 1 is elevated, distinct spectral changes first occur at 130 K: the peak at 340 cm –1 shifts to a more intense and a much broader peak that is centered at 360 cm –1 , the latter being indicative of a Ru-(OS)O vibrational stretch; 43 , 44 ,54 the peak at 540 cm –1 also becomes stronger at this temperature, where the η 2 -(OS)O isomer contributes more significantly to the deformation mode of SO 2 . 44 These spectral shifts naturally reflect changes in vibrational modes that one would expect to be associated with the η 1 -OSO to η 2 -(OS)O transition.…”

“…Single-crystal Raman spectroscopy on 1 was employed to characterize its molecular structure and thermal stability in more detail. Detailed experimental procedures for all of these in situ light-induced single-crystal characterization methods are given by Cole et al 43 …”

“…This finding 34 led to the subsequent discovery of several more [RuSO 2 ] complexes that display nano-optomechanical transduction, 39 , 40 , 43 − 46 including trans -[Ru(SO 2 )(NH 3 ) 4 (3-bromopyridine)]tosylate 2 and trans -[Ru(SO 2 )(NH 3 ) 4 (3-iodopyridine)]tosylate 2 . Both of these complexes were found to exhibit nano-optomechanical transduction with 100% η 1 -OSO photoisomer formation.…”