Phapale Daulat, Ghosh Rajib, Das Dipanwita
Department of Chemistry, Institute of Chemical Technology , Nathalal Parekh Marg, Matunga, Mumbai 400019, India.
Radiation and Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India.
Inorg Chem. 2017 Jun 5;56(11):6310-6317. doi: 10.1021/acs.inorgchem.7b00412. Epub 2017 May 24.
A new tris-heteroleptic complex Ru(bpy)(dppz)(OSO), 1 (bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine and OSO = 2-methylsulfinylbenzoate), was synthesized and characterized to control the photochromic Ru-S → Ru-O linkage isomerization. Details isomerization kinetics studied by UV-visible absorption spectroscopy and cyclic voltammetry revealed that efficient photochromic S → O isomerization and thermal O → S reversal take place in solvents like propylene carbonate (PC), methanol, and dichloromethane. Strikingly, photoisomerization of 1 is arrested in water although is active in the analogous compound Ru(bpy)(OSO). Effective excited state deactivation through dark MLCT state involving dppz ligand of 1 switches off photochromism in aqueous medium. Interestingly, the photochromism is activated in aqueous solution in the presence of DNA which shields the dppz localized dark state through intercalation. Ultrafast transient absorption spectroscopic measurement sheds light on the differential behavior of photochromism in aqueous and nonaqueous solvents.
合成并表征了一种新型三杂配体配合物Ru(bpy)(dppz)(OSO)，即1（bpy = 2,2'-联吡啶，dppz = 二吡啶并[3,2-a:2',3'-c]吩嗪，OSO = 2-甲基亚磺酰苯甲酸酯），以控制光致变色的Ru-S→Ru-O键异构化。通过紫外可见吸收光谱和循环伏安法研究的详细异构化动力学表明，在碳酸亚丙酯（PC）、甲醇和二氯甲烷等溶剂中发生了有效的光致变色S→O异构化和热O→S逆转。引人注目的是，1的光异构化在水中停止，尽管在类似化合物Ru(bpy)(OSO)中是活跃的。通过涉及1的dppz配体的暗态金属-配体电荷转移（MLCT）状态进行的有效激发态失活，在水介质中关闭了光致变色。有趣的是，在DNA存在的情况下，光致变色在水溶液中被激活，DNA通过插入作用屏蔽了dppz局部暗态。超快瞬态吸收光谱测量揭示了光致变色在水性和非水性溶剂中的不同行为。
