Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands
Unusually Efficient Pyridine Photodissociation from Ru(II) Complexes with Sterically Bulky Bidentate Ancillary Ligands
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DOI：
10.1021/jp5057732
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发表时间：
2014-11-13
影响因子：
2.9
通讯作者：
Turro, Claudia
中科院分区：
文献类型：
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作者：
Knoll, Jessica D.;Albani, Bryan A.;Turro, Claudia
通过在双齿配体[Ru(Tpy)(Bpy)(Py)](2+)(1；tpy=2，2‘：2’，6-terpyridine；bpy=2，2‘-bipyridine；py=2，2’-biquinine)中引入空间位阻，提供了[Ru(Tpy)(Me(2)bpy)(Py)](2+)(2；Me(2)bpy=6，6‘-二甲基-2，2’-联吡啶)和[Ru(Tpy)(Biq)(Py)](2+)[Ru(Tpy)(Biq)(Py)](3；biq=2，2‘-biquoline)，在可见光下促进了吡啶的光解离.在CH3CN(Gimel(Irr)=500 nm)中，2和3发生配体交换生成相应的[Ru(Tpy)(NN)(NCCH3)](2+)(NN=Me(2)bpy，biq)配合物，其量子产率F500分别为0.16(1)和0.033(1)。这些值表明，在类似的实验条件下，与1，F500和0.0001相比，反应效率提高了2-3个数量级。2和3在H2O中用低能光光解生成[Ru(Tpy)(NN)(OH2)](2+)(NN=Me2bpy，biq)也进行得很快(gimel(Irr)>；590 nm)。在相似的实验条件下，配合物1-3在CH3CN和H2O中的黑暗中都是稳定的。X-射线晶体结构和理论计算表明，双齿配体2和3的平面相对于1有明显的扭曲。由双齿配体Me2bpy和Biq定义的晶体二面角分别为67.87度和61.89度，而在bpy和tpy之间只观察到很小的八面体几何构型扭曲，1，83.34度。Me2bpy和biq提供的空间位阻也分别导致吡啶配体在2和3中相对于1发生较大的扭曲，这被认为削弱了其与金属的S键和p-背键，并在光诱导配体交换的效率中起着至关重要的作用。2和3与Gimel(Irr)>；590 nm进行配体交换的能力使它们有可能成为构建含吡啶结合基团的药物的光化学治疗剂的潜在候选者。
The introduction of steric bulk to the bidentate ligand in [Ru(tpy)(bpy)(py)](2+) (1; tpy = 2,2':2',6?-terpyridine; bpy = 2,2'-bipyridine; py = pyridine) to provide [Ru(tpy)(Me(2)bpy)(py)](2+) (2; Me(2)bpy = 6,6'-dimethyl-2,2'-bipyridine) and [Ru(tpy)(biq)(py)](2+) (3; biq = 2,2'-biquinoline) facilitates photoinduced dissociation of pyridine with visible light. Upon irradiation of 2 and 3 in CH3CN (gimel(irr) = 500 nm), ligand exchange occurs to produce the corresponding [Ru(tpy)(NN)(NCCH3)](2+) (NN = Me(2)bpy, biq) complex with quantum yields, F500, of 0.16(1) and 0.033(1) for 2 and 3, respectively. These values represent an increase in efficiency of the reaction by 2-3 orders of magnitude as compared to that of 1, F500 < 0.0001, under similar experimental conditions. The photolysis of 2 and 3 in H2O with low energy light to produce [Ru(tpy)(NN)(OH2)](2+) (NN = Me2bpy, biq) also proceeds rapidly (gimel(irr) > 590 nm). Complexes 1-3 are stable in the dark in both CH3CN and H2O under similar experimental conditions. X-ray crystal structures and theoretical calculations highlight significant distortion of the planes of the bidentate ligands in 2 and 3 relative to that of 1. The crystallographic dihedral angles defined by the bidentate ligand, Me2bpy in 2 and biq in 3, and the tpy ligand were determined to be 67.87 degrees and 61.89 degrees, respectively, whereas only a small distortion from the octahedral geometry is observed between bpy and tpy in 1, 83.34 degrees. The steric bulk afforded by Me2bpy and biq also result in major distortions of the pyridine ligand in 2 and 3, respectively, relative to 1, which are believed to weaken its s-bonding and p-back-bonding to the metal and play a crucial role in the efficiency of the photoinduced ligand exchange. The ability of 2 and 3 to undergo ligand exchange with gimel(irr) > 590 nm makes them potential candidates to build photochemotherapeutic agents for the delivery of drugs with pyridine binding groups.