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Diastereoselective Synthesis and Two-Step Photocleavage of Ruthenium Polypyridyl Complexes Bearing a Bis(thioether) Ligand
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2019-08-21 00:00:00 , DOI: 10.1021/acs.inorgchem.9b01669
Michael S. Meijer 1 , Sylvestre Bonnet 1
Affiliation  

Thioethers are good ligands for photoactivatable ruthenium(II) polypyridyl complexes, as they form thermally stable complexes that are prone to ligand photosubstitution. Here, we introduce a novel symmetric chelating bis(thioether) ligand scaffold, based on 1,3-bis(methylthio)-2-propanol (4) and report the synthesis and stereochemical characterization of the series of novel ruthenium(II) polypyridyl complexes [Ru(bpy)2(L)](PF6)2 ([1]–[3](PF6)2), where L is ligand 4, its methyl ether, 1,3-bis(methylthio)-2-methoxypropane (5), or its carboxymethyl ether, 1,3-bis(methylthio)-2-(carboxymethoxy)propane (6). Coordination of ligands 46 to the bis(bipyridine)ruthenium center gives rise to 16 possible isomers, consisting of 8 possible Λ diastereoisomers and their Δ enantiomers. We found that the synthesis of [1]–[3](PF6)2 is diastereoselective, yielding a racemic mixture of the Λ-(S)-eq-(S)-ax-OHeq-[Ru]2+ and Δ-(R)-ax-(R)-eq-OHeq-[Ru]2+ isomers. Upon irradiation with blue light in water, [1]–[3](PF6)2 selectively substitute their bis(thioether) ligands for water molecules in a two-step photoreaction, ultimately producing [Ru(bpy)2(H2O)2]2+ as the photoproduct. The relatively stable photochemical intermediate was identified as cis-[Ru(bpy)21-L)(H2O)]2+ by mass spectrometry. Global fitting of the time evolution of the UV–vis absorption spectra of [1]–[3](PF6)2 was employed to derive the photosubstitution quantum yields (Φ443) for each of the two photochemical reaction steps separately, revealing very high quantum yields of 0.16–0.25 for the first step and lower values (0.0055–0.0093) for the second step of the photoreaction. The selective and efficient photochemical reaction makes the photocleavable bis(thioether) ligand scaffold reported here a promising candidate for use in e.g. ruthenium-based photo-activated chemotherapy.

中文翻译:

带有双(硫醚)配体的钌多吡啶基配合物的非对映选择性合成和两步光解

硫醚是可光活化的钌(II)聚吡啶基配合物的良好配体,因为它们会形成易于配体光稳定的热稳定配合物。在这里,我们介绍一种基于1,3-双(甲硫基)-2-丙醇(4)的新型对称螯合双(硫醚)配体支架,并报道了一系列新型钌(II)聚吡啶基配合物的合成和立体化学表征[Ru(bpy)2(L)](PF 62([ 1 ] – [ 3 ](PF 62),其中L为配体4,其甲基醚为1,3-双(甲硫基)-2 -甲氧基丙烷(5)或其羧甲基醚,1,3-双(甲硫基)-2-(羧甲氧基)丙烷(6)。配位体的配位4 - 6到双(联吡啶)钌中心产生了16分可能的异构体,包括8个可能的非对映异构Λ和它们的Δ对映体。我们发现[ 1 ] – [ 3 ](PF 62的合成是非对映选择性的,产生Λ-(S)-eq-(S)-ax-OH eq- [ Ru ] 2+和Δ-(R)-ax-(R)-eq-OH eq- [ Ru ] 2+异构体。在水中用蓝光照射后,[ 1 ]-[ 3 ](PF 62在两步光反应中选择性地将其双(硫醚)配体替换为水分子,最终产生[Ru(bpy)2(H 2 O) )2 ] 2+作为光产物。相对稳定的光化学,鉴定为中间体顺式- [吡啶钌2(κ 1 -L)(H 2 O)] 2+通过质谱法。[ 1 ] – [ 3 ](PF 6)的紫外可见吸收光谱时间演化的全局拟合2被用来导出所述photosubstitution量子产率(Φ 443每个的两个光化学反应步骤)分开,露出0.16-0.25非常高的量子产率为的第二步骤中的第一步骤和较低的值(0.0055-0.0093)光反应。选择性和有效的光化学反应使光可裂解的双(硫醚)配体支架在此报道,成为用于例如钌基光活化化学疗法的有前途的候选者。
更新日期:2019-08-21
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