Light-Induced Sulfur to Oxygen Isomerization of Ruthenium Sulfoxide Complexes Jackson Majher

Rhodopsin Photoswitchable molecules: molecules which change optically and electronically due to activation via electromagnetic radiation. Examples: Oxazine Sodium nitroprusside Kim, J. E.; McCamant, D. W.; Zhu, L.; Mathies, R. A.; J. Phys. Chem. B 2001, 105, 1240–1249. (2) Rymo, F. M.; J. Phys. Chem. A 2012, 116 (48), 11888-11895 (3) Woike, T., Krasser, W., Bechthold, P. S., Haussuhl, S.; Phys. Rev. Lett. 1984, 53, 767–1770.

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[Ru(bpy)2(OSO)]+ -Relatively large quantum yield (0.45) achieved. -Chelate effects changes mechanism -Ruthenium (w/ sulfoxide character) to * bpy transition assigned. -No evidence of O-bonded 3MLCT excited state. -Vibrationally relaxed 3MLCT 2 structure proposed. (11) McClure, B. A.; Mockus, N. V.; Butcher, D. P.; Lutterman, D. A.; Turro, C.; Petersen, J. L.; Rack, J. J.; Inorg. Chem. 2009, 48, 8084–8091.

-Transient absorption spectroscopy utilized for kinetic information. Summary: -Series of ruthenium sulfoxide complexes that undergo SO isomerization were synthesized. -Characterization by electronic absorbance spectroscopy, IR, NMR and cyclic voltammetry. -Transient absorption spectroscopy utilized for kinetic information. -Results show picosecond timescale kinetics, suggestive of a mechanism including rapid nonradiative decay through conical intersection. (12) McClure, B. A.; Abrams, E. R.; Rack, J. J.; J. Am. Chem. Soc. 2010, 132, 5428-5436. Goals of Paper: -Study relationship between distortion energy and isomerization reactivity. -Effect of changing electronic and steric factors contributing to exited state isomerization.

Absorption Spectra: -Absorption shift to lower wavelengths for BnF5 -Absorption applies to the d* transition. -fwhm highest for R=BnF5 complex which suggests larger nuclear displacement between ground and triplet excited state. -fwhm analysis showed metal-ligand contribution as being the major source of distortion.

Analysis Continued.. -Zero-zero energy was calculated using known values and the absorption spectra to predict room temperature wavelength emission at 1070, 1530, and 1780 nm for R = Nap, BnF5, and Bn respectively. -Were unable measure emission at these wavelengths though they did not see any emission from 500-850 nm. -Emission max observed at 580, 576, and 572 nm for R = Nap, Bn, BnF5 respectively (77K). -Further testing required to see if NIR emission observed. -Relevant information: Strong affect of metal-ligand vibrations on absorption spectra and PES has temperature dependence. E0 = Eop - * - ST

Picosecond Transient Absorption O-Bonded Isomer S-Bonded Isomer: 1.0, 2.0, 5.0, 10.3, 20.4, 50.4 101.1, 203.0, 508.0, 1008 ps 5.0, 10.2, 20.3, 50.7, 100.3, 495.3 ps

R = Me

Conclusions: Criticisms: -Distortion energy plays a large role in isomerization through conical intersections, primarily through metal-ligand interactions. -R = BnF5 complex shows good isomerization characteristics, electronic influence through sulfur bond achievable. -More testing needs to be done to narrow down specific electronic and steric factors needed to maximize isomerization conditions. Criticisms: -Not a significant expansion of knowledge past their previous work. -Would be helpful to include more R group types to solidify trends observed. -No computational calculations that provide reasoning to their results. -Emission calculations not backed up by any experimental data.

Acknowledgements: And Eric R. Abrams Beth McClure J. J. Rack

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