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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Biomimetic iron(III) complexes of facially and meridionally coordinating tridentate 3N ligands: tuning of regioselective extradiol dioxygenase activity in organized assemblies
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Biomimetic iron(III) complexes of facially and meridionally coordinating tridentate 3N ligands: tuning of regioselective extradiol dioxygenase activity in organized assemblies

机译:面部和子午配位的三齿3N配体的仿生铁(III)配合物:在有组织的程序集的区域选择性外二醇二加氧酶活性的调整。

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摘要

Four mononuclear iron(III) complexes of the type [Fe(L)Cl_3] 1-4, where L is a tridentate 3N ligand such as(2-pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine (L1), (methyl)(2-pyridin-2-ylethyl)(pyridin-2-ylmethyl) amine (L2), bis(pyridin-2-ylethyl)amine (L_3), and (1-methyl-1H-imidazol-2-ylmethyl)(pyridin-2-ylethyl) amine (L4), have been isolated and studied as functional models for catechol dioxygenase enzymes. In[Fe(L2)Cl_3] 2, the ligand L2 is coordinated facially to iron(III) whereas in [Fe(L1)Cl_3] 1 and [Fe(L4)Cl_3] 4 the ligands L1 and L4 are coordinated meridionally. In DCM, CH_3CN and aqueous SDS, CTAB and TX-100 micellar media, the positions of both the low and high energy catecholate-to-iron(III) LMCT bands (465-530, 690-860 nm) observed for the 3,4-di-tert-butylcatecholate (DBC~(2-)) adducts of the iron(III) complexes vary in the order 2 >1 >3 >4, which reflects the influence of the stereoelectronic factors, mode of coordination and the chelate ring size formed by the tridentate ligands. Spectral and electrochemical studies disclose the formation and location of the cationic adducts as solvated [Fe(L)(DBC)(H_2O)]~+ species mostly in the aqueous micellar pseudophases of SDS and TX-100 and in the aqueous phase of CTAB micellar solution. The [Fe(L)(DBC)Cl] adducts of 1, 3 and 4, generated in situ, afford major amounts of intradiol cleavage products (17.0-70.0%) and smaller amounts of extradiol (1.2-4.2%) products with varying extradiol to intradiol cleavage product selectivity (E/I: 1, 0.08: 1; 3, 0.02: 1; 4, 0.3: 1). On the other hand, interestingly, the adduct [Fe(L2)(DBC)Cl] of 2 generated in DCM yields a major amount of extradiol (54.0%) and a lower amount (18.3%) of the intradiol cleavage products (E/I, 3: 1). Remarkably, in aqueous SDS micellar media, it shows exclusive extradiol cleavage products (79.4%) while all the other complexes show very low selectivity (E/I: 1, 0.03: 1; 2, 79.4: 0, 3, 0.06: 1, 4, 0.06: 1), suggesting the suitability of SDS medium for 2 to elicit exclusive extradiol cleavage. The TX-100 micellar medium also provides a suitable hydrophobic environment for 2 to elicit extradiol cleavage. However, in CTAB micellar medium, 2 shows cleavage selectivity lower than others. Also, the rate of dioxygenation is higher in SDS micellar medium than in DCM, and is dependent upon the chelate ring size.
机译:四个[Fe(L)Cl_3] 1-4类型的单核铁(III)配合物,其中L是三齿3N配体,例如(2-吡啶-2-基乙基)(吡啶-2-基甲基)胺(L1) ,(甲基)(2-吡啶-2-基乙基)(吡啶-2-基甲基)胺(L2),双(吡啶-2-基乙基)胺(L_3)和(1-甲基-1H-咪唑-2- ylmethyl)(pyridin-2-ylethyl)胺(L4)已被分离出来,并作为儿茶酚双加氧酶的功能模型进行了研究。在[Fe(L2)Cl_3] 2中,配体L2在表面上与铁(III)配位,而在[Fe(L1)Cl_3] 1和[Fe(L4)Cl_3] 4中,配体L1和L4在子午方向上配位。在DCM,CH_3CN和SDS水溶液,CTAB和TX-100胶束介质中,观察到的低能量和高能量儿茶酸-铁(III)LMCT谱带(465-530,690-860 nm)的位置,铁(III)配合物的4-二叔丁基邻苯二酚(DBC〜(2-))加合物的变化顺序为2> 1> 3> 4,这反映了立体电子因素,配位方式和螯合物的影响三齿配体形成的环大小。光谱和电化学研究揭示了溶剂化的[Fe(L)(DBC)(H_2O)] +阳离子形式的阳离子加合物的形成和位置,主要存在于SDS和TX-100的胶束假相的水溶液中以及CTAB胶束的水相中解。原位生成的1、3和4的[Fe(L)(DBC)Cl]加合物可提供大量的二醇内裂解产物(17.0-70.0%)和少量的二醇间异丁酮(1.2-4.2%)产物,外二醇对二醇内切割产物的选择性(E / I:1,0.08:1; 3,0.02:1; 4,0.3:1)。另一方面,有趣的是,DCM中生成的2的加合物[Fe(L2)(DBC)Cl]产生大量的二醇(54.0%)和较低的(18.3%)的二醇内裂解产物(E / I,3:1)。值得注意的是,在水性SDS胶束介质中,它显示出独家的二醇外裂解产物(79.4%),而所有其他复合物都显示出非常低的选择性(E / I:1、0.03:1、2、79.4:0、3、0.06:1, 4,4,6:1),表明SDS培养基适合2引起排他性二醇裂解。 TX-100胶束介质还为2提供了合适的疏水环境,以引起二醇外切。但是,在CTAB胶束介质中,2的裂解选择性低于其他。同样,在SDS胶束介质中,双加氧的速率比在DCM中更高,并且取决于螯合环的大小。

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