Tripathy Suman Kumar, van der Meer Margarethe, Sahoo Anupam, Laha Paltan, Dehury Niranjan, Plebst Sebastian, Sarkar Biprajit, Samanta Kousik, Patra Srikanta
School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar - 751007, India.
Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstraße 34-36, D-14195 Berlin, Germany.
Dalton Trans. 2016 Aug 2;45(31):12532-8. doi: 10.1039/c6dt01995a.
The reaction of the chloro-bridged dimeric precursor [{(p-cym)Ru(II)Cl}(μ-Cl)]2 (p-cym = p-cymene) with the bridging ligand 3,6-bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine (bpytz) in ethanol results in the formation of the dinuclear complex {(p-cym)Ru(II)Cl}2(μ-bpytz˙(-)), 1. The bridging tetrazine ligand is reduced to the anion radical (bpytz˙(-)) which connects the two Ru(II) centres. Compound 1 has been characterised by an array of spectroscopic and electrochemical techniques. The radical anion character has been confirmed by magnetic moment (corresponding to one electron paramagnetism) measurement, EPR spectroscopic investigation (tetrazine radical anion based EPR spectrum) as well as density functional theory based calculations. Complex 1 displays two successive one electron oxidation processes at 0.66 and 1.56 V versus Ag/AgCl which can be attributed to {(p-cym)Ru(II)C}2(μ-bpytz˙(-))/{(p-cym)Ru(II)Cl}2(μ-bpytz) and {(p-cym)Ru(II)Cl}2(μ-bpytz)/{(p-cym)Ru(III)Cl}2(μ-bpytz) processes (couples I and II), respectively. The reduction processes (couple III-couple V), which are irreversible, likely involve the successive reduction of the bridging ligand and the metal centres together with loss of the coordinated chloride ligands. UV-Vis-NIR spectroelectrochemical investigation reveals typical tetrazine radical anion containing bands for 1 and a strong absorption in the visible region for the oxidized form 1, which can be assigned to a Ru(II) → π* (tetrazine) MLCT transition. The assignment of spectroscopic bands was confirmed by theoretical calculations.
氯桥联二聚体前体[{(对异丙基苯)钌(II)氯}(μ - 氯)]₂（对异丙基苯 = 对异丙基苯）与桥联配体3,6 - 双(3,5 - 二甲基吡唑基)-1,2,4,5 - 四嗪（bpytz）在乙醇中反应，生成双核配合物{(对异丙基苯)钌(II)氯}₂(μ - bpytz˙(-))，即1。桥联四嗪配体被还原为阴离子自由基（bpytz˙(-)），它连接两个Ru(II)中心。化合物1已通过一系列光谱和电化学技术进行了表征。通过磁矩测量（对应单电子顺磁性）、电子顺磁共振光谱研究（基于四嗪自由基阴离子的电子顺磁共振谱）以及基于密度泛函理论的计算，证实了自由基阴离子的性质。配合物1相对于Ag/AgCl在0.66和1.56 V处显示出两个连续的单电子氧化过程，这可分别归因于{(对异丙基苯)钌(II)氯}₂(μ - bpytz˙(-))/{(对异丙基苯)钌(II)氯}₂(μ - bpytz)和{(对异丙基苯)钌(II)氯}₂(μ - bpytz)/{(对异丙基苯)钌(III)氯}₂(μ - bpytz)过程（氧化还原对I和II）。不可逆的还原过程（氧化还原对III - 氧化还原对V）可能涉及桥联配体和金属中心的连续还原以及配位氯配体的损失。紫外 - 可见 - 近红外光谱电化学研究揭示了1中典型的含四嗪自由基阴离子的谱带以及氧化形式1在可见光区域的强吸收，这可归因于Ru(II)→π*（四嗪）的金属 - 配体电荷转移跃迁。光谱带的归属通过理论计算得到了证实。
