Photoactivity of Mono- and Dicarbonyl Complexes of Ruthenium(II) Bearing an N,N,S-Donor Ligand: Role of Ancillary Ligands on the Capacity of CO Photorelease

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• 作者：Margarita A. Gonzalez ; Samantha J. Carrington ; Indranil Chakraborty ; Marilyn M. Olmstead ; Pradip K. Mascharak
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：October 7, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：11320-11331
• 全文大小：559K
• 年卷期：v.52,no.19(October 7, 2013)
• ISSN：1520-510X

文摘

One monocarbonyl and one dicarbonyl complex of ruthenium(II), namely, [Ru(Cl)(CO)(qmtpm)(PPh₃)]BF₄ (2) and [Ru(Cl)(CO)₂(qmtpm)]ClO₄ (3), derived from the tridentate ligand 2-quinoline-N-(2鈥?methylthiophenyl)methyleneimine (qmtpm) have been synthesized and structurally characterized. The qmtpm ligand binds in a meridional fashion in these carbonyl complexes, and in 3, the two carbon monoxide (CO) ligands are cis to each other. Solutions of 2 in ethanol, chloroform, or acetonitrile rapidly release CO upon illumination with low-power (3鈥?5 mW) light in the 300鈥?50 nm range. Loss of CO from 2 brings about a dramatic color change from yellow to magenta because of the formation of [Ru(Cl)(MeCN)(qmtpm)(PPh₃)]BF₄ (4). In acetonitrile, photorelease of CO from 3 under 360 nm light occurs in two steps, and the violet photoproduct [Ru(Cl)(MeCN)₂(qmtpm)]⁺ upon reaction with Ag⁺ and PPh₃ affords red [Ru(MeCN)₂(qmtpm)(PPh₃)](ClO₄)₂ (5). The structure of 5 has also been determined by X-ray crystallography. Reduced myoglobin assay confirms that 2 and 3 act as photoactive CO-releasing molecules (photoCORMs) that deliver 1 and 2 equiv of CO, respectively. The results of density functional theory (DFT) and time-dependent DFT studies confirm that electronic transitions from molecular orbitals with predominantly Ru鈥揅O character to ligand-based 蟺* orbitals facilitate CO release from these two photoCORMs. Complexes 2鈥?b>5 have provided an additional opportunity to analyze the roles of the ancillary ligands, namely, PPh₃, Cl^{鈥?/sup>, and MeCN, in shifting the positions of the metal-to-ligand charge-transfer bands and the associated sensitivity of the two photoCORMs to different wavelengths of light. Collectively, the results provide helpful hints toward the future design of photoCORMs that release CO upon exposure to visible light.}