Elsevier

Inorganica Chimica Acta

Volume 357, Issue 14, 15 November 2004, Pages 4291-4296
Inorganica Chimica Acta

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Photoirradiation reactions and crystal structures of two geometrical isomers of [Ru(OAc)(2cqn)2NO] (H2cqn=2-chloro-8-quinolinol)

https://doi.org/10.1016/j.ica.2003.09.003Get rights and content

Abstract

The photoirradiation reactions of two geometrical isomers (cis-1 and cis-2) of [Ru(OAc)(2cqn)2NO] (H2cqn=2-chloro-8-quinolinol) were studied. Cis-2 [Ru(OAc)(2cqn)2NO] (2) photochemically isomerized to cis-1 [Ru(OAc)(2cqn)2NO] (1) in CH2Cl2 or DMSO using an Xe lamp as a light source and the reaction was irreversible. The 2 to 1 isomerization coexisting with 15NO gas and its evolution of the 1H NMR spectra showed that the dissociation and recombination of both the NO and the acetate ion involve in the isomerization. On the other hand, 1 did not isomerize but the NO ligand exchanged with 15NO. The crystal structures of 1 and 2 were determined by X-ray diffraction.

The photoirradiation reactions and crystal structures of two isomers (cis-1 and cis-2) of [Ru(OAc)(2cqn)2NO] (H2cqn=2-chloro-8-quinolinol) were studied. The cis-2 isomer (2) photochemically isomerized to the cis-1 isomer (1) in CH2Cl2 or DMSO using an Xe lamp as a light source. The isomerization coexisting with 15NO gas and its evolution of the 1H NMR spectra showed that the dissociation and recombination of both the NO and the acetate ion involve in the isomerization. On the other hand, 1 did not isomerize but the NO ligand exchanged with 15NO.

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Introduction

Nitrogen monoxide (NO) has been long interested to inorganic chemists because of its versatile binding modes and reactivities with transition metals [1], [2], [3]. In connection with NO activity in biological system in recent years, nitrosylruthenium(II) complexes have been widely noticed as useful delivery reagents of NO to biological target [4], [5], [6], [7], [8]. The nitrosylruthenium(II) complex that is thermally stable but photochemically active to release NO would be employed as the NO delivery [6]. So, study on the photochemical and thermochemical reactivities of nitrosylruthenium(II) complexes is necessary to understand the reaction mechanism and to design the NO delivery.

The authors have studied on the photochemical and thermal activities of the nitrosylruthenium(II) complexes containing 8-quinolinolato and its derivatives [9], [10]; the [RuX(qn)2NO] (X=Cl, OAc; Hqn=8-quinolinol derivatives in which the 2-position is substituted with the electron-donating group, such as methyl or ethyl group) photochemically and thermally isomerized, while the [RuX(qn)2NO] (Hqn=8-quinolinol and its derivatives containing the electron-attracting group, such as chloro group) thermally isomerized.

The thermal reactivity of two isomers of [Ru(OAc)(2cqn)2NO] (H2cqn=2-chloro-8-quinolinol) was researched in detail [11]. The thermal stability depended considerably on the geometrical configuration of the complexes; cis-2 [Ru(OAc)(2cqn)2NO] is stable below 373 K, while cis-1 [Ru(OAc)(2cqn)2NO] isomerized to its cis-2 isomer at 343 K. However, at 413 K, the 2cqn ligands in the two isomers reacted to afford the coordinated 2oqn (H2oqn=2, 8-quinolinediol) and qn-O-qn (Hqn-O-qnH=bis(8-hydroxyquinoline-2-yl) ether). The schematic structures of cis-1 and cis-2 isomers are shown in Fig. 1.

In this paper, the photoirradiation reactions of the cis-1 and cis-2 isomers of [Ru(OAc)(2cqn)2NO] in the presence of 14NO or 15NO were studied using an Xe lamp. The crystal structures of the isomers of [Ru(OAc)(2cqn)2NO] were determined by X-ray diffraction.

Section snippets

Photoirradiation reactions of cis-1 and cis-2[Ru(OAc)(2cqn)2NO]

Cis-1 [Ru(OAc)(2cqn)2NO] (complex 1) and cis-2 [Ru(OAc)(2cqn)2NO] (complex 2) were prepared according to [9] and confirmed by the 1H NMR spectra.

The experimental scale and procedure for the photoirradiation reaction of 1 were the same as those of 2. After 1 (0.07 mmol) dissolved in CH2Cl2 (25 cm3) was degassed by three freeze-pump-thaw cycles on a high vacuum line, nitrogen monoxide (2 mmol) was trapped into a Pyrex vessel containing the CH2Cl2 solution at liquid nitrogen temperature. After the

Molecular structures of the complexes

Molecular structures of 1 and 2 are shown in Fig. 2, Fig. 3 with the atomic numbering schemes, respectively. The selected bond distances and angles are shown in Table 2. The NO is essentially linear with the Ru, reflecting that the complexes are of the {RuII–NO+} type. The Ru–NO and N–O bond distances are similar to the typical values in other linear nitrosylruthenium(II) complexes [9], [10], [11].

In 1 and 2, the OAc ligand is cis to the NO and the O atom of one of the 2cqn ligands is trans to

Supplementary material

Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 211271 and 211272 for complexes 1 and 2, respectively. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-336-033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

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1

Present address: Protein Research Group, RIKEN Genomic Sciences Center (GSC), The Institute of Physical and Chemical Research, Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan.

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