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We report the excited-state behavior of a structurally simple bis -sulfoxide complex, cis -S,S-[Ru(bpy) 2 (dmso) 2 ] 2+ , as investigated by femtosecond pump–probe spectroscopy. The results reveal that a single photon prompts phototriggered isomerization of one or both dmso ligands to yield a mixture of cis -S,O-[Ru(bpy) 2 (dmso) 2 ] 2+ and cis -O,O-[Ru(bpy) 2 (dmso) 2 ] 2+ . The quantum yields of isomerization of each product and relative product distribution are dependent upon the excitation wavelength, with longer wavelengths favoring the double isomerization product, cis -O,O-[Ru(bpy) 2 (dmso) 2 ] 2+ . Transient absorption measurements on cis -O,O-[Ru(bpy) 2 (dmso) 2 ] 2+ do not reveal an excited-state isomerization pathway to produce either the S,O or S,S isomers. Femtosecond pulse shaping experiments reveal no change in the product distribution. Pump–repump–probe transient absorption spectroscopy of cis -S,S-[Ru(bpy) 2 (dmso) 2 ] 2+ shows that a pump–repump time delay of 3 ps dramatically alters the S,O : O,O product ratio; pump–repump–probe transient absorption spectroscopy of cis -O,O-[Ru(bpy) 2 (dmso) 2 ] 2+ with a time delay of 3 ps uncovers an excited-state isomerization pathway to produce the S,O isomer. In conjunction with low-temperature steady-state emission spectroscopy, these results are interpreted in the context of an excited-state bifurcating pathway, in which the isomerization product distribution is determined not by thermodynamics, but rather as a dynamics driven reaction.
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Photocrystallography of [Ru(bpy) 2 (dmso) 2 ] 2+ reveals an O-bonded metastable state
We report the first instance of observing the phototriggered isomerization of dmso ligands on a bis sulfoxide complex, [Ru(bpy) 2 (dmso) 2 ], in the crystalline solid state. The solid-state UV-vis spectrum of the crystal demonstrates an increase in optical density around 550 nm after irradiation, which is consistent with the solution isomerization results. Digital images of the crystal before and after irradiation display a notable color change (pale orange to red) and cleavage occurs along planes, (1̄01) and (100), during irradiation. Single crystal X-ray diffraction data also confirms that isomerization is occurring throughout the lattice and a structure that contains a mix of the S , S and O , O / S , O isomer was attained from a crystal irradiated ex situ . In situ irradiation XRD studies reveal that the percentage of the O-bonded isomer increases as a function of 405 nm exposure time.
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- PAR ID:
- 10429087
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Chemical Science
- ISSN:
- 2041-6520
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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