Abstract
The photorelease of nitric oxide (NO·) has been investigated in dimethylsulfoxide (DMSO) on two compounds of formula [Ru(R-tpy)(bpy)(NO)](PF6)3, in which bpy stands for 2,2′-bipyridine and R-tpy for the 4′-R-2,2′:6′,2″-terpyridine with R = H and MeOPh. It is observed that both complexes are extremely sensitive to traces of water, leading to an equilibrium between [Ru(NO)] and [Ru(NO2)]. The photoproducts of formula [Ru(R-tpy)(bpy)(DMSO)](PF6)2 are further subjected to a photoreaction leading to a reversible linkage isomerization between the stable Ru-DMSO(S) (sulfur linked) and the metastable Ru-DMSO(O) (oxygen linked) species. A set of 4 [Ru(R-tpy)(bpy)(DMSO)]2+ complexes (R = H, MeOPh, BrPh, NO2Ph) is investigated to characterize the ratio and mechanism of the isomerization which is tentatively related to the difference in absorbance between the Ru-DMSO(S) and Ru-DMSO(O) forms. In addition, the X-ray crystal structures of [Ru(tpy)(bpy)(NO)](PF6)3 and [Ru(MeOPh-tpy)(bpy)(DMSO(S))](PF6)2 are presented.
Highlights
Nitric oxide (NO·) is a radical involved in numerous biological functions, such as blood pressure regulation, stimulation of immune response or neurotransmission, which has been observed to exhibit various anticancer, antibacterial, and anti-inflammatory activities [1]
DMSO is a potential ligand for ruthenium complexes [14]
DMSO (DMSO-d6) is shown in Figure 2a. 1 H-NMR appears to be an excellent tool for defining the coordination sphere of [Ru(tpy)(bpy)X] species
Summary
Nitric oxide (NO·) is a radical involved in numerous biological functions, such as blood pressure regulation, stimulation of immune response or neurotransmission, which has been observed to exhibit various anticancer, antibacterial, and anti-inflammatory activities [1]. To overpass the frequently modest solubility of metal-nitrosyl complexes in biological media, the complexes are generally dissolved in aqueous solutions containing a maximum in volume of 0.5% of dimethylsulfoxide (DMSO) before being tested on living cells. In this context, the stability and photochemical reactivity of [Ru(NO)] species in DMSO is naturally addressed. [RuT1B0(NO)]3+ has been selected as a benchmark candidate for NO· release, due to its “push-pull” character between the electron-rich methoxyphenyl and the electron-withdrawing nitrosyl (NO) substituents. 40 -(4-(bromo)phenyl)-2,20 :60 ,2”-terpyridine and 40 -(4-(nitro)phenyl)-2,20 :60 ,2”-terpyridine, respectively, will be presented to fully investigate the possibilities for Ru-DMSO(S) to Ru-DMSO(O) linkage isomerizations (Figure 1)
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