Controlling water exchange rates in potential Mn<sup>2+</sup>-based MRI agents derived from NO2A<sup>2−</sup>
作者:Rosa Pujales-Paradela、Fabio Carniato、David Esteban-Gómez、Mauro Botta、Carlos Platas-Iglesias
DOI:10.1039/c9dt00211a
日期:——
associative nature of the water exchange reaction. A potentially decadentate ligand containing two NO2A units linked by a xylenyl spacer in the meta position was also synthesised. The corresponding binuclear Mn2+ complex contains two metal ions with different hydration numbers, as evidenced by 1H NMRD and 17O NMR measurements. DFT calculations show that this is related to the presence of a bridging bidentate
我们报告了一系列基于1,4,7-三氮杂环壬烷-1,4-二乙酸(H 2 NO2A)的五齿配体,其中的大环单元的第三个氮原子具有不同的取代基。相应的Mn 2+配合物的详细1 H核磁弛豫分散(NMRD)表征表明,在含有内球水分子的溶液中形成了六配位物质。通过记录横向17 O弛豫时间和化学位移测量值可以证实这一点。发现配位水分子的水交换速率受三氮杂环壬烷单元第7位的取代基R的性质的强烈影响(R = Me,k 298 ex= 62.6×10 7 s -1 ; R = Bz,k 298 ex = 4.4×10 7 s -1 ; R = 1-苯乙基,k 298 ex= 2.6×10 7 s -1)。降低的交换率是由取代基的体积增加所解释的,这阻碍了进入的水分子以缔合活化的水交换机制进入。DFT计算(M062X / TZVP)支持了这一点,该计算确定了水交换反应的缔合性质。包含由二甲苯基间隔物在连接的两个