NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY OF LANTHANIDE COMPLEXES WITH A TETRAACETIC TETRAAZA MACROCYCLE - UNUSUAL CONFORMATION PROPERTIES
NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY OF LANTHANIDE COMPLEXES WITH A TETRAACETIC TETRAAZA MACROCYCLE - UNUSUAL CONFORMATION PROPERTIES
复制标题
DOI：
10.1021/ic50207a042
复制
发表时间：
1980-01-01
影响因子：
4.6
通讯作者：
DESREUX, JF
中科院分区：
文献类型：
--
作者：
DESREUX, JF
从大环的立体动力学行为和乙酸酯基团的不稳定性方面分析了1，4，7，10-四氮杂环十二烷-N，N '，N”，N“-四乙酸（DOTA）的抗磁性和顺磁性镧系元素配合物的~（13）C NMR谱。在室温以下，烯属基团在NMR时间尺度上是刚性的。在高温下，快速的环反转是可能的，能垒很高。在LaDOTA的情况下，通过线形分析获得以下动力学参数：AG* m= 60.7±1.2 kJ mol-1，AH*= 59.4±0.8 kJ mol-1，和AS*=-4.6 3. 3 J K-1 mol-1。类似的势垒测量顺magneticcomplex。大环的所有烯属基团在低温下采用相同的构象。这种空间排列导致了一种新的类型的温度依赖性的不对称性，出现在NMR谱的不稳定的乙酸酯基团。的Eu（III），Pr（III），Yb（III）与DOTA配合物的结构推导出这些化合物所表现出的大的顺磁位移的相对大小。氮-镧系元素距离约为2.85 A，金属位于大环下方。
The and 13C NMR spectra of diamagnetic and paramagnetic lanthanide complexes with 1, 4, 7, 10-tetraazacyclododecane-/V,/V', TV",/V'"-tetraacetic acid (DOTA) are analyzed in terms of the stereodynamic behavior of the macrocycle and of the lability of the acetate groups. Below room temperature, the ethylenic groups are rigid on the NMR time scale. Rapid ring inversion is achievedat elevated temperature, the energy barrier being very high. The following kinetic parameters are obtained by line-shape analysis in the case of LaDOTA: AG* m= 60.7±1.2 kJ mol-1, AH*= 59.4±0.8 kJ mol-1, and AS*=-4.6±3.3 J K-1 mol-1. Similar energy barriers are measured for paramagneticcomplexes. All the ethylenic groups of the macrocycle adopt the same conformation at low temperatures. This spatial arrangement leads to a new type of temperature-dependent asymmetry which appears in the NMR spectra of the labile acetate groups. The structureof the Eu (III), Pr (III), and Yb (III) complexes with DOTA is deduced from the relative magnitude of the large paramagnetic shifts exhibited by these compounds. The nitrogen-lanthanide distance is approximately 2.85 A, and the metal is located under the macrocycle.