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首页> 外文期刊>Inorganic Chemistry: A Research Journal that Includes Bioinorganic, Catalytic, Organometallic, Solid-State, and Synthetic Chemistry and Reaction Dynamics >Revelation of Varying Bonding Motif of Alloxazine, a Flavin Analogue, in Selected Ruthenium(II/III) Frameworks
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Revelation of Varying Bonding Motif of Alloxazine, a Flavin Analogue, in Selected Ruthenium(II/III) Frameworks

机译：黄素类似物别恶嗪的键合基序在某些钌（II / III）骨架中的启示

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The reaction of alloxazine (L) and Ru-II(acac)(2)(CH3CN)(2) (acac(-) = acetylacetonate) in refluxing methanol leads to -the simultaneous formation of Ru-II(acac)(2)(L) (1 = bluish-green) and Ru-III(acac)(2)(L-) (2 = red) encompassing a usual neutral alpha-iminoketo chelating form of L and an unprecedented monodeprotonated alpha-iminoenolato chelating form of L-, respectively. The crystal structure of 2 establishes that N5,O4(-) donors of L- result in a nearly planar five-membered chelate with the {Ru-III(acac)(2)(+)} metal fragment. The packing diagram of 2 further reveals its hydrogen-bonded dimeric form as well as pi-pi interactions between the nearly planar tricyclic rings of coordinated alloxazirie ligands in nearby molecules. The paramagnetic 2 and one-electron-oxidized 1(+) display ruthenium(III)-based anisotropic axial EPR in CH3CN at 77 K with < g >/Delta g of 2.136/0.488 and 2.084/0.364, respectively (< g > = {1/3(g(1)(2) + g(2)(2) g(3)(2))}(1/2), and Delta g= g(1)-g(3)). The multiple electron-transfer processes of 1 and 2 in CH3CN -have been analyzed by DFT-calculated MO compositions and Mulliken spin density distributions at the paramagnetic states, which suggest successive two-electron uptake by the pi-system of the heterocyclic ring of L (L -> L center dot- -> L2-) or L- (L- -> L center dot 2- -> L3-) besides metal-based (Ru-II/Ru-III) redox process. The origin of the ligand as well as mixed metal-ligand-based multiple electronic transitions of 1(n) (n = +1, 0, -1, -2) and 2(n) (n = 0, -1, -2) in the UV and -visible regions, respectively, has been assessed by TD-DFT calculations in each redox state. The pK(a) values of 1 and 2 incorporating two and one NH protons of 6.5 (N3H, pK(a1))/8.16 (N1H, pK(a2)) and 8.43 (N1H, pK(a1)), respectively, are estimated by monitoring their spectral Changes as a function of pH in CH3CN-H2O (1:1). 1 and 2 in.CH3CN also participate in proton-driven internal reorganizations involving- the coordinated alloxatine moiety, i.e., transformation of an alpha-iminoketo chelating form to an alpha-iminoenolato chelating form and the reverse process without any electron-transfer step: Ru-II(acac)(2)(L) (1) -> Ru-II(acac)(2)(L-) (2(-)) and Ru-III(acac)(2)(L-) (2) -> Ru-III(acac)(2)(L) (1(+)).
机译：甲恶嗪（L）与Ru-II（acac）（2）（CH3CN）（2）（acac（-）=乙酰丙酮）在回流甲醇中的反应导致-Ru-II（acac）（2）同时形成（L）（1 =蓝绿色）和Ru-III（acac）（2）（L-）（2 =红色）包含L的常见中性α-亚氨基螯合形式和史无前例的单去质子化α-亚氨基螯合形式L-分别。 2的晶体结构确定L-的N5，O4（-）供体导致与{Ru-III（acac）（2）（+）}金属片段形成近乎平面的五元螯合物。 2的堆积图进一步揭示了它的氢键二聚体形式以及附近分子中配位的四氮杂配体的近平面三环之间的pi-pi相互作用。顺磁性2和单电子氧化1（+）在CH3CN中在77 K下显示基于钌（III）的各向异性轴向EPR，其 /Δg分别为2.136 / 0.488和2.084 / 0.364（ = {1/3（g（1）（2）+ g（2）（2）g（3）（2））}（1/2），并且增量g = g（1）-g（3））。通过DFT计算的MO组成和顺磁态下的Mulliken自旋密度分布分析了CH3CN中1和2的多次电子转移过程，这表明L杂环的pi系统连续吸收了两个电子除了基于金属的（Ru-II / Ru-III）氧化还原工艺外，还可以使用（L-> L中心点--> L2-）或L-（L--> L中心点2--> L3-）。配体以及1（n）（n = + 1、0，-1，-2）和2（n）（n = 0，-1，- 2）在每种氧化还原状态下，通过TD-DFT计算分别评估了UV和可见光区域中的光。 1和2的pK（a）值分别包含两个和一个NH质子6.5（N3H，pK（a1））/ 8.16（N1H，pK（a2））和8.43（N1H，pK（a1））通过监测其在CH3CN-H2O（1：1）中作为pH的函数的光谱变化来估算。 CH3CN中的1和2也参与了质子驱动的内部重组，其中涉及-协调的四氧嘧啶部分，即将α-亚氨基酮螯合形式转化为α-亚氨基烯醇螯合形式以及没有任何电子转移步骤的逆过程：Ru -II（acac）（2）（L）（1）-> Ru-II（acac）（2）（L-）（2（-））和Ru-III（acac）（2）（L-）（ 2）-> Ru-III（acac）（2）（L）（1（+））。

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