Crystal structure, solution properties and hydrolytic activity of an alkoxo-bridged dinuclear copper(ii) complex, as a ribonuclease model
作者:Tamás Gajda、Attila Jancsó、Satu Mikkola、Harri Lönnberg、Holger Sirges
DOI:10.1039/b108948j
日期:——
Crystal structures, solution properties and ribonuclease activity of copper(II) complexes of a binucleating, bis-pyridyl ligand (N,N′-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol, L) have been investigated. The single-crystal X-ray structure of the mononuclear complex [CuL(ClO4)2] (1) shows distorted octahedral geometry around the metal ion, with the four nitrogens of the ligand in the equatorial plane of copper(II). A μ-alkoxo-bridged dinuclear complex is formed in the presence of a two-fold metal excess. Despite the symmetrical ligand, the two metal ions in [Cu2(LH−1)(DPP)(ClO4)(CH3OH)]ClO4 (2, DPP = diphenyl phosphate) have distinct, distorted octahedral (Cu1) and square pyramidal (Cu2) geometry. Beside the alkoxo-oxygen, the phosphate
group of DPP also bridges the two metal centers in 2 in a μ-1,3-bridging mode. The complexes formed in aqueous solution are likely to have analogous structures to 1 and 2. The dinuclear [Cu2(LH−1)(OH)] complex efficiently promotes the hydrolysis/transesterification of both activated (2-hydroxypropyl p-nitrophenyl phosphate, hpnp) and non-activated, biological phosphodiesters (uridine-2′,3′-cyclic-monophosphate, cUMP and uridylyl-(3′,5′)-uridine, UpU). For example, a 2 mM solution of the dinuclear complex provides 5 orders of magnitude acceleration in the hydrolysis of cUMP. The proposed mechanisms include double Lewis-acid activation with intramolecular general base catalysis.
我们研究了双核双
吡啶配体(N,N′-双(2-
吡啶基甲基)-1,3-二
氨基丙-2-醇,L)的
铜(II)配合物的晶体结构、溶液性质和
核糖核酸酶活性。单核复合物 [CuL(
ClO4)2] (1) 的单晶 X 射线结构显示出
金属离子周围的扭曲八面体几何形状,
配体的四个硝基位于
铜(II)的赤道面上。在
金属过量两倍的情况下,形成了一个μ-烷氧基桥接的双核配合物。尽管
配体是对称的,但[Cu2(LH-1)(
DPP)( )(CH3OH)] (2,
DPP =
磷酸二苯酯)中的两个
金属离子具有不同的扭曲八面体(Cu1)和正方
金字塔(Cu2)几何形状。除了烷氧基外,
DPP 的
磷酸基团还以μ-1,3 桥接模式桥接 2 中的两个
金属中心。在
水溶液中形成的配合物可能具有与 1 和 2 类似的结构。双核[Cu2(LH-1)(OH)]配合物能有效地促进活化的(2-羟基丙基
对硝基苯磷酸酯,hpnp)和非活化的
生物磷酸二酯(
尿苷-2′,3′-环状单
磷酸酯,c
UMP 和
尿苷-(3′,5′)-
尿苷,UpU)的
水解/酯化。例如,2 mM 的双核复合物溶液可使 c
UMP 的
水解速度加快 5 个数量级。提出的机理包括分子内通用碱催化的双
路易斯酸活化。