Efficiency of Photodissociation of Carbonyl Ligand in Ruthenium Monocarbonyl Bipyridine Complexes: Effect of Isomeric Structures and Ligands
Photoactivated CO-releasing molecules have potential medical applications. <i>trans</i>(Cl,Cl)-[Ru(bpy)(CO)<sub>2</sub>Cl<sub>2</sub>] (bpy = 2,2'-bipyridine) efficiently releases the first CO ligand (∼100% quantum yield), but the second CO dissociation is inefficient, and its precise quantum yield remains undetermined. Photodissociation of <i>trans</i>(Cl,Cl)-[Ru(bpy)(CO)<sub>2</sub>Cl<sub>2</sub>] yielded two monocarbonyl complexes, <i>cis</i>(Cl,Cl),<i>trans</i>(Cl,CH<sub>3</sub>CN)-[Ru(bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>] and <i>trans</i>(Cl,Cl)-[Ru(bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>], as the major and minor stereoisomeric products, respectively. The apparent quantum yields for the second CO dissociations were 0.56% and 0.78% for <i>cis</i>(Cl,Cl),<i>trans</i>(Cl,CH<sub>3</sub>CN)- and <i>trans</i>(Cl,Cl)-isomers, respectively. Considering the efficient photoisomerization of the <i>trans</i>(Cl,Cl)- to <i>cis</i>(Cl,Cl),<i>trans</i>(Cl,CH<sub>3</sub>CN)-isomer, the <i>trans</i>(Cl,Cl)-isomer would have a higher quantum yield. We also isolated the monocarbonyl complex after the first CO dissociation of <i>trans</i>(Cl,Cl)-[Ru(6Mes-bpy)(CO)<sub>2</sub>Cl<sub>2</sub>] (6Mes-bpy = 6,6'-dimesityl-2,2'-bipyridine), which contains bulky substituents at the 6,6'-positions of the bpy ligand. X-ray crystal structure analysis revealed the selective formation of <i>trans</i>(Cl,Cl)-[Ru(6Mes-bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>]. The quantum yield for the second CO dissociation from this structure was found to be 2.0%, nearly four times larger than that of <i>cis</i>(Cl,Cl),<i>trans</i>(Cl,CH<sub>3</sub>CN)-[Ru(bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>]. Time-resolved IR (TRIR) measurements demonstrated that photoirradiation of <i>cis</i>(Cl,Cl),<i>trans</i>(Cl,CH<sub>3</sub>CN)-[Ru(bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>] produced a five-coordinate pyramidal square intermediate with a stronger Ru-CO bond than in the ground state. In contrast, no such intermediate was observed for <i>trans</i>(Cl,Cl)-[Ru(6Mes-bpy)(CO)(CH<sub>3</sub>CN)Cl<sub>2</sub>]. The presence of this intermediate is thought to be a key factor in inhibiting further CO dissociation.
Authors
- Mari Toyama (ORCID: https://orcid.org/0000-0002-3451-0063)
- Noriharu Nagao (ORCID: https://orcid.org/0000-0001-9109-2382)
- Ken Onda (ORCID: https://orcid.org/0000-0003-1724-2009)
- Seiichi Tanaka (ORCID: https://orcid.org/0009-0005-2591-1729)
- Yusuke Kuramochi (ORCID: https://orcid.org/0000-0001-5936-5010)
- Jun Itabashi
- Hitoshi Ishida (ORCID: https://orcid.org/0000-0002-6457-0083)
Institutions
- Tokyo Institute of Technology (JP)
- Kyushu University (JP)
- Meiji University (JP)
- Kyoto University (JP)
- Kansai University (JP)
- Kitasato University (JP)
- Kindai University (JP)
Publication Details
- Journal
- Inorganic Chemistry
- Published
- 2025-06-30
- DOI
- https://doi.org/10.1021/acs.inorgchem.5c00466
- Citations
- 1
- Primary Topic
- Covalent Organic Framework Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.52
Funders
- Japan Society for the Promotion of Science