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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Valence structures of the diastereomeric complexes meso- andrac-[Ru_2(acac)_4(μ-Q)]~n (n = 2–, 1–, 0, 1+, 2+) with the multiple quinonoidbridging ligand Q = 1,2,4,5-tetraimino-3,6-diketocyclohexane
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Valence structures of the diastereomeric complexes meso- andrac-[Ru_2(acac)_4(μ-Q)]~n (n = 2–, 1–, 0, 1+, 2+) with the multiple quinonoidbridging ligand Q = 1,2,4,5-tetraimino-3,6-diketocyclohexane

机译：具有多个醌型桥配体Q = 1的中和消旋-[Ru_2（acac）_4（μ-Q）]〜n（n = 2–，1–，0、1 +，2 +）非对映体复合物的价结构2,4,5-四亚氨基-3,6-二酮环己烷

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摘要

Mesa- and rac-configurated diastereoisomers [Ru_2(acac)_4(μ-Q)] have been separated and identified as species through a crystal structure analysis of the mesa form. The presence of two redox-active{Ru(acac)_2} groups (acac~- = 2,4-pentanedionate) and quinonoid Q with two equivalent π-conjugatedα-diimine chelate sites and one p-quinone function allowed for the full cyclic voltammetric andspectroelectrochemical (UV-vis-NIR, IR, EPR) characterisation of the five accessible states (2-, 1-, 0,1+ and 2+ forms) for both isomers. Oxidation occurs at the metal ions to produce Ru~(II)Ru~(III)mixed-valent states [Ru_2(acac)_4(μ-Q)]~+ (K_c≈ 10~(4.5)) with corresponding EPR features but withoutdetectable intervalence absorption in the near infrared region. IR-spectroelectrochemistry revealsopposite frequency shifts for the v(C=O) and v(NH) stretching vibrations on reduction and oxidation,in agreement with the assumed electronic structure. Reduction leads to strongly stabilised[Ru_2(acac)_4(μ-Q)]~- states (K_c≈10~(11)) which show weak NIR shoulders around 1040 nm. The EPRcharacteristics are remarkably different for the two isomeric monoanions, reflecting presumably flexiblegeometry and electronic structure. The observation of broad but detectable EPR resonance at roomtemperature in solution and the g factor anisotropy in the glassy frozen state at 110 K suggest a ratherevenly metal-ligand mixed singly occupied MO. Together with the ZINDO calculations and the partialexperimental results reported previously by Masui et al. (Inorg. Chem., 2000, 39, 141) for[Ru_2(bpy)_4(μ-Q)]~(n+)(n =2, 3, 4), the characteristic differences provide an insight into the electronicfeatures such as mixed valency manifestations and the variable extent of mixing of the metal-quinonefrontier orbitals of these systems involving Ru~(II)-stabilised Q which is unknown as a free ligand.
机译：通过台面形式的晶体结构分析，已分离并配置了台面和外消旋构型的非对映异构体[Ru_2（acac）_4（μ-Q）]。两个具有氧化还原活性的{Ru（acac）_2}基团（acac〜-= 2,4-戊二酮酸酯）和具有两个等效π-共轭α-二亚胺螯合位点和一个对苯醌功能的醌型Q允许全环两种异构体的五个可及状态（2-，1-，0,1 +和2+形式）的伏安和光谱电化学（UV-vis-NIR，IR，EPR）表征。氧化发生在金属离子上，产生具有相应EPR特征的Ru〜（II）Ru〜（III）混合价态[Ru_2（acac）_4（μ-Q）]〜+（K_c≈10〜（4.5）），但在近红外区域没有可检测到的间隔吸收。红外光谱电化学揭示了还原和氧化时v（C = O）和v（NH）拉伸振动的相反频移，与假定的电子结构一致。还原导致强烈稳定的[Ru_2（acac）_4（μ-Q）]〜-状态（K_c≈10〜（11）），其在1040 nm附近显示弱的NIR肩。两种异构单阴离子的EPR特征显着不同，反映了可能的几何形状和电子结构。在室温下溶液中观察到广泛但可检测到的EPR共振，并在110 K的玻璃态冻结状态下观察到g因子各向异性，表明金属-配体混合均匀占据了MO。连同Masui等人先前报道的ZINDO计算和部分实验结果。 （Inorg。Chem。，2000，39，141）对于[Ru_2（bpy）_4（μ-Q）]〜（n +）（n = 2，3，4），特性差异提供了对诸如这些系统涉及Ru〜（II）-稳定的Q的混合化合价表现形式和金属-醌前沿轨道的混合混合程度，其未知为游离配体。

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