This study will use ligand steric parameters to investigate the photosensitivity of the compound [Ru(biq)2(dpb)]2+, which will be compared with already known complex, [Ru(biq)2(dpb)Re(CO)4] (biq = 2,2'-bipyridine and dpb = 2,3-bis(2-pyridyl)benzoquinoxaline). The former complex photocatalytically decomposes into [Ru(biq)2(CH3CN)2]2+ while the latter remains inactive. Both complexes were previously investigated by Turro et al. X-ray data for [Ru(biq)2(dpb)](PF6)2 and [Ru(biq)2(CH3CN)2](PF6)2 were collected at the Advanced Light Source through the SCRALS program. The solid angle (Ω), G-parameter (% metal coordination sphere shielded by the ligand) and steric congestion (Γ) will be evaluated through the use of the Solid-G program package. In the complex [Ru(biq)2(dpb)]2+, the biq-ligands were closer to the metal center than the dpb-ligand (average Ru-N distance of 1.636 Å versus 1.661 Å, respectively) and possess larger Gx-parameters (36.28 % versus 32.61 %, respectively). The steric congestion G(Γ) associated with this complex was calculated to be 8.98 % and the unfavorable interactions associated between the ligands (VG) was 0.27 Å3. These parameters represent significant steric interactions between the ligands. Upon photolysis the complex decayed into [Ru(biq)2(dpb)]2+ where VG and steric congestion decreased to 0.11 Å3 and 8.31 %, respectively, which indicate a relaxation of the steric interactions. The average Ru-N distances decreased slightly with average Ru-N distances of 1.620 Å increasing the Gx-parameters associated with the biq ligands to 36.61 %. The steric interactions of [Ru(biq)2(dpb)]2+ will also be compared to the bimetallic compound [Ru(biq)2(dpb)Re(CO)4]. The coordination of the Re-moiety increases VG to 0.39 Å3, thus increasing the steric strain while lowering the overall Metal-Ligand-Charge-Transfer energy.

Steric effects associated with the photolysis of a Ru(II) polypyridyl complex

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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