2,2'-联吡啶基酮（dpk）作为配合物[（dpk）（Cl）Ru（mu-tppz）Ru（Cl）（dpk）] n +的辅助受体和报告配体，其中tppz = 2,3,5,6-四（2-吡啶基）吡嗪。,Inorganic Chemistry

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2,2'-联吡啶基酮（dpk）作为配合物[（dpk）（Cl）Ru（mu-tppz）Ru（Cl）（dpk）] n +的辅助受体和报告配体，其中tppz = 2,3,5,6-四（2-吡啶基）吡嗪。
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2006 Sep 18 , DOI: 10.1021/ic060887l
Sandeep Ghumaan ₁ , Biprajit Sarkar ₁ , Nripen Chanda ₁ , Monika Sieger ₁ , Jan Fiedler ₁ , Wolfgang Kaim ₁ , Goutam Kumar Lahiri ₁

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tppz桥联的钌（II）络合物[（dpk）（Cl）Ru（II）（mu-tppz）Ru（II）（Cl）（dpk）]（ClO4）2，[2]（ClO4）2和单核[（dpk）（Cl）Ru（II）（tppz）]（ClO4），[1]（ClO4）[tppz = 2,3,5,6-四（2-吡啶基）吡嗪，dpk = 2,2 '-二吡啶基酮]，已经合成。[2] 2+中连续的单电子氧化对之间的260 mV间隔转换为中间体的2.5 x 10（4）的相对较小的比例常数Kc。结果表明，电化学数据（E（ox），E（red），Kc）如何在一系列系统[[L] ClRu（mu-tppz）RuCl（L）] n中反映辅助配体L的供体/受体效应，尤其是L和tppz在金属中电子密度之间的竞争。根据EPR（g1 = 2.470，g2 = 2.195和g3 = 1。在4 K时为873），中间体[2] 3+为混合价Ru（II）Ru（III）物种，在1800 nm（ε= 1500 M（-1））下显示出相当窄的间隔电荷转移（IVCT）带厘米（-1））。IVCT带的700 cm（-1）的半高宽度（Deltanu（1/2））远小于使用Hush公式Deltanu（1 / 2）=（2310E（op））（1/2）（E（op）= 5556 cm（-1），IVCT跃迁的能量），适用于局部（II类）混合价Ru（II） Ru（III）体系。[2] 3+中的价离域化由Ru（II）Ru（II）中N，N'配位的dpk配体从1676 cm（-1）的nu（C = O）带的均匀移动来支持Ru（2.5）Ru（2.5）形式的1690 cm（-1）的前体，说明使用dpk受体通过游离但pi共轭的有机羰基作为报告配体。考虑到混合价的“边界”或“混合”“ II-III类”概念以及协调方面（即双三齿性质），正在讨论Kc的中等值与IVCT窄带之间的明显矛盾。 pi受体桥联配体的结构。总之，复合离子[1] +和[2] 2+分别显示四个和五个连续的还原过程，涉及基于tppz和dpk的未占据pi轨道。单电子还原形式[2] +已被指定为包含tppz *-自由基阴离子的物质，该物质在4K（g（平行）= 2.002，g（垂直）= 1.994）上表现出自由基型EPR信号。）和一个中等强度的基于配体的低能带在965 nm（ε= 1100 M（-1）cm（-1））。

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2,2'-Dipyridylketone (dpk) as ancillary acceptor and reporter ligand in complexes [(dpk)(Cl)Ru(mu-tppz)Ru(Cl)(dpk)]n+ where tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine.

The tppz-bridged diruthenium(II) complex [(dpk)(Cl)Ru(II)(mu-tppz)Ru(II)(Cl)(dpk)](ClO4)2, [2](ClO4)2, and mononuclear [(dpk)(Cl)Ru(II)(tppz)](ClO4), [1](ClO4) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine, dpk = 2,2'-dipyridylketone], have been synthesized. The 260 mV separation between successive one-electron oxidation couples in [2]2+ translates to a relatively small comproportionation constant, Kc, of 2.5 x 10(4) for the intermediate. It is shown how electrochemical data (E(ox), E(red), Kc) reflect the donor/acceptor effects of ancillary ligands L in a series of systems [(L)ClRu(mu-tppz)RuCl(L)]n, particularly the competition between L and tppz for electron density from the metal. According to EPR (g1 = 2.470, g2 = 2.195, and g3 = 1.873 at 4 K) the intermediate [2]3+ is a mixed-valent Ru(II)Ru(III) species which shows a rather narrow intervalence charge transfer (IVCT) band at 1800 nm (epsilon = 1500 M(-1) cm(-1)). The width at half-height (Deltanu(1/2)) of 700 cm(-1) of the IVCT band is much smaller than the calculated value of 3584 cm(-1), obtained by using the Hush formula Deltanu(1/2) = (2310E(op))(1/2) (E(op) = 5556 cm(-1), energy of the IVCT transition) which would be applicable to localized (Class II) mixed-valent Ru(II)Ru(III) systems. Valence delocalization in [2]3+ is supported by the uniform shift of the nu(C=O) band of the N,N'-coordinated dpk ligands from 1676 cm(-1) in the Ru(II)Ru(II) precursor to 1690 cm(-1) in the Ru(2.5)Ru(2.5) form, illustrating the use of the dpk acceptor to act as reporter ligand via the free but pi-conjugated organic carbonyl group. The apparent contradiction between the moderate value of Kc and the narrow IVCT band is being discussed considering "borderline" or "hybrid" "Class II-III" concepts of mixed-valency, as well as coordination aspects, i.e., the bis-tridentate nature of the pi-acceptor bridging ligand. Altogether, the complex ions [1]+ and [2]2+ display four and five successive reduction processes, respectively, involving both tppz- and dpk-based unoccupied pi orbitals. The one-electron reduced form [2]+ has been assigned as a tppz*- radical-anion-containing species which exhibits a free-radical-type EPR signal at 4K (g(parallel) = 2.002, g(perpendicular) = 1.994) and one moderately intense ligand-based low-energy band at 965 nm (epsilon = 1100 M(-1) cm(-1)).

更新日期：2017-01-31

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