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.

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Velazquez-Garcia, Jose de J 

Recent discoveries of a range of single-crystal optical actuators are feeding a new form of materials chemistry, given their broad range of potential applications, from light-induced molecular motors to light sensors and optical-memory media. A series of ruthenium-based coordination complexes that exhibit sulfur dioxide linkage photoisomerization is of particular interest because they exhibit single-crystal optical actuation via either optical switching or nano-optomechanical transduction processes. We report the discovery of a new complex in this series of chemicals, [Ru(SO2)(NH3)4(3-fluoropyridine)]tosylate2 (1), which forms an η1-OSO photoisomer with 70% photoconversion upon the application of 505 nm light. The uncoordinated oxygen atom in this η1-OSO photoisomer impinges on one of the arene rings in a neighboring tosylate counter ion of 1 just enough that incipient nano-optomechanical transduction is observed. The structure and optical properties of this actuator are characterized via in situ light-induced single-crystal X-ray diffraction (photocrystallography), single-crystal optical absorption spectroscopy and microscopy, as well as single-crystal Raman spectroscopy. These materials-characterization methods were also used to track thermally induced reverse isomerization processes in 1. One of these processes involves an η1-OSO to η2-(OS)O transition, which was found to proceed sufficiently slowly at 110 K that its structural mechanism could be determined via a time sequence of photocrystallography experiments. The resulting data allowed us to structurally capture the transition, which was shown to occur via a form of coordination isomerism. Our newfound knowledge about this structural mechanism will aid the molecular design of new [RuSO2] complexes with functional applications.

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J Phys Chem C Nanomater Interfaces
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American Chemical Society (ACS)
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BASF/Royal Academy of Engineering Research Chair in Data-Driven Molecular Engineering of Functional Materials (part of STFC via the ISIS Neutron and Muon Source); the 1851 Royal Commission of the Great Exhibition (2014 Fellowship in Design); U.S. Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences, and used research resources of the Center for Nanoscale Materials, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, supported by the U.S. DOE, all under contract no. DE-AC02-06CH11357; National Council of Science and Technology of Mexico (CONACyT) and the Cambridge Trust for a PhD Scholarship (217553).