Ruthenium polypyridyl complexes may act as light-activatable anticancer prodrugs provided that they are protected by well-coordinated ligands that i) prevent coordination of other biomolecules to the metal center in the dark and ii) can be removed by visible light irradiation. In this paper, the use of monodentate thiol ligands RSH as light-cleavable protecting groups for the ruthenium complex [Ru(tpy)(bpy)(OH2)](PF6)2 ([1](PF6)2; tpy=2,2';6',2″-terpyridine, bpy=2,2'-bypyridine), is investigated. The reaction of [1](2+) with RSH=H2Cys (L-cysteine), H2Acys (N-acetyl-L-cysteine), and HAcysMe (N-acetyl-L-cysteine methyl ester), is studied by UV-visible spectroscopy, NMR spectroscopy, and mass spectrometry. Coordination of the monodentate thiol ligands to the ruthenium complex takes place upon heating to 353 K, but full conversion to the protected complex [Ru(tpy)(bpy)(SR)]PF6 is only possible when a large excess of ligand is used. Isolation and characterization of the two new thiolato complexes [Ru(tpy)(bpy)(κS-HCys)]PF6 ([2]PF6) and [Ru(tpy)(bpy)(κS-HAcys)]PF6 ([3]PF6) is reported. [3]PF6 shows a metal-to-ligand charge-transfer absorption band that is red shifted (λmax=492 nm in water) compared to its methionine analogue [Ru(tpy)(bpy)(κS-HAmet)](Cl)2 ([5](Cl)2, λmax=452 nm; HAmet=N-acetyl-methionine). In the dark the thiolate ligand coordinated to ruthenium is oxidized even by traces of oxygen, which first leads to the sulfenato, sulfinato, and disulfide ruthenium complexes, and finally to the formation of the aqua complex [1](2+). [3]PF6 showed slow photosubstitution of the thiolate ligand by water under blue light irradiation, together with faster photooxidation of the thiolate ligand compared to dark conditions. The use of thiol vs. thioether monodentate ligands is discussed for the protection of anticancer ruthenium-based prodrugs.

译文

钌多吡啶复合物可以充当可光活化的抗癌前药,前提是它们受到配位良好的配体的保护,即i) 阻止其他生物分子在黑暗中与金属中心的配位,ii) 可以通过可见光去除照射。在本文中,使用单齿硫醇配体RSH作为钌配合物 [Ru(tpy)(bpy)(OH2)](PF6)2 ([1](PF6)2; tpy = 2,2 ';6',2 ”-特吡啶,研究了bpy = 2,2 '-bypyridine)。研究了 [1](2) 与RSH = H2Cys (L-半胱氨酸),H2Acys (N-乙酰基-L-半胱氨酸) 和HAcysMe (N-乙酰基-L-半胱氨酸甲酯) 的反应。紫外可见光谱,NMR光谱和质谱。在加热至353 K时,发生单齿硫醇配体与钌络合物的配位,但是只有当使用大量过量的配体时,才可能完全转化为受保护的络合物 [Ru(tpy)(bpy)(SR)]PF6。报道了两种新的硫代络合物 [Ru(tpy)(bpy)(κ s-HCys)]PF6 ([2]PF6) 和 [Ru(tpy)(bpy)(κ s-HAcys)]PF6 ([3]PF6) 的分离和表征。[3] 与甲硫氨酸类似物 [Ru(tpy)(bpy)(κ s-HAmet)](Cl)2 ([5](Cl)2相比,PF6显示出红移的金属-配体电荷转移吸收带 (在水中 λ max = 492 nm),Λ max = 452 nm; HAmet = N-乙酰基-甲硫氨酸)。在黑暗中,与钌配位的硫醇盐配体甚至被痕量的氧氧化,这首先导致磺胺酸酯,磺胺酸酯和二硫化物钌配合物,最后形成水配合物 [1](2)。[3]PF6显示,在蓝光照射下,硫醇盐配体被水的光取代缓慢,并且与黑暗条件相比,硫醇盐配体的光氧化更快。讨论了使用硫醇与硫醚单齿配体保护基于钌的抗癌前药。

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