Abstract

Two stable Ru(II) bipyridyl complexes were synthesized with the deprotonated forms of the azo ligands of 8-hydroxyquinoline (hq) as analogues and they were chromatographically separated. The extended azo ligands coordinated as a bidentate ligand and chelates to ruthenium(II) through 8-quinolinolate moiety, leaving the azo part free from coordination. The general formula of the complexes are [Ru(bpy)₂(q)]⁺. Here, q− is the deprotonated form of 5-phenylazo-8-hydroxyquinoline (Hq¹) and 5-(2-naphthylazo)-8-hydroxyquinoline (Hq²). The complexes were verified by ¹H NMR, ESI-mass, absorption-emission spectra, cyclic voltammetry and single-crystal X-ray structure determination. UV light-induced trans → cis isomerization and reverse isomerism i.e. cis → trans around -N=N- bond at room temperature were proposed from the UV-Vis spectral changes as well as the changing of the colour of the solution of the complexes. In aid of understanding the electronic charge distribution and charge-transfer properties, computational studies employing DFT and TDDFT method have been executed.

Graphic abstract

Significant alteration in absorption spectra and colour change was observed for trans-cis photo-isomerization of the complexes upon UV light irradiation due to presence of free rotating azo groups

中文翻译：

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带有8-羟基喹啉偶氮配体的联吡啶钌（II）配合物的合成，晶体结构，DFT计算和反式→顺式异构化研究

摘要

以8-羟基喹啉（hq）的偶氮配体的去质子化形式作为类似物，合成了两种稳定的Ru（II）二吡啶基配合物，并进行了色谱分离。延伸的偶氮配体作为双齿配体配位并且通过8-喹啉酸酯部分与钌（II）螯合，而使偶氮部分不受配位。配合物的通式为[Ru（bpy）₂（q）] ⁺。在此，q-是5-苯基偶氮-8-羟基喹啉（Hq ¹）和5-（2-萘基偶氮）-8-羟基喹啉（Hq ²）的去质子化形式。配合物由¹验证1 H NMR，ESI质量，吸收发射光谱，循环伏安法和单晶X射线结构测定。根据紫外-可见光谱变化以及配合物溶液颜色的变化，提出了紫外光诱导的反式→顺式异构化和反向异构现象，即室温下顺式→反式围绕-N = N-键。为了帮助理解电子电荷分布和电荷转移特性，已经进行了使用DFT和TDDFT方法的计算研究。

图形摘要

由于存在自由旋转的偶氮基团，在紫外光照射下，复合物的反式顺式光异构化观察到吸收光谱和颜色变化显着