Geraldes C F, Brown R D, Brucher E, Koenig S H, Sherry A D, Spiller M
Department of Chemistry, University of Texas at Dallas, Richardson 75083-0688.
Magn Reson Med. 1992 Oct;27(2):284-95. doi: 10.1002/mrm.1910270208.
Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths have been measured for a series of neutral Gd(3+)-triazamacrocyclic complexes and compared with previous data for the simplest member of the macrocyclic triaza series, Gd(NOTA), and for the widely studied linear triaza complex, Gd(DTPA)2-. Water proton relaxivities and their temperature dependence were found to vary widely with the size of the triaza macrocycle and the identity of the side-chain chelating groups. The number of rapidly exchanging water molecules directly coordinated to the Gd3+ ion (q) was found to vary from 2 to 4 for eight of the ten complexes examined and a linear relationship between the 50-MHz relaxivity value and integral values of q is presented for this series of complexes. tau s values derived from ESR linewidths for some of the complexes are in reasonable agreement with those derived from their NMRD profiles; however, those complexes which either tended to form aggregates in solution or gave evidence for multiple averaged solution structures showed broad, near Lorentzian linewidths which were clearly not dominated by the electron spin relaxation time (tau s).
已对一系列中性钆（Ⅲ）-三氮杂大环配合物测量了核磁共振弛豫色散（NMRD）曲线和电子顺磁共振线宽，并与大环三氮杂系列最简单成员钆（NOTA）以及广泛研究的线性三氮杂配合物钆（DTPA）2-的先前数据进行了比较。发现水质子弛豫率及其温度依赖性随三氮杂大环的大小和侧链螯合基团的性质而有很大变化。在所研究的十个配合物中的八个中，直接与钆3+离子配位的快速交换水分子数（q）在2到4之间变化，并且给出了该系列配合物的50兆赫兹弛豫率值与q积分值之间的线性关系。从某些配合物的电子顺磁共振线宽得出的τs值与从其NMRD曲线得出的值合理一致；然而，那些倾向于在溶液中形成聚集体或显示出多种平均溶液结构证据的配合物显示出宽的、接近洛伦兹线宽，显然不受电子自旋弛豫时间（τs）支配。
