Effect of the regiochemistry of butyl amide substituents on the solution-state structures of lanthanide(III) DOTA-tetraamide complexes.
Effect of the regiochemistry of butyl amide substituents on the solution-state structures of lanthanide(III) DOTA-tetraamide complexes.
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DOI：
10.1021/ic9017008
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发表时间：
2009-11-02
影响因子：
4.6
通讯作者：
Woods, Mark
中科院分区：
文献类型：
--
作者：
Mani, Tomoyasu;Tircso, Gyula;Zhao, Piyu;Sherry, A. Dean;Woods, Mark
dota -四酰胺镧系配合物的配位几何是决定其水交换动力学的关键因素。控制dota -四酰胺配合物的水交换动力学，并通过扩展其配位几何，是特别感兴趣的，因为这类配合物作为PARACEST MRI造影剂的潜在应用。为了在最低的预饱和功率下促进最大的CEST效果，需要比这些类型的配合物通常观察到的慢得多的交换动力学。因此，采用交换较慢的方形反棱镜配位几何的配合物是优选的；然而，决定哪一种配位几何是首选的因素仍然不清楚。一系列具有不同区域异构体构型的丁酰胺取代基的dota -四酰胺配合物为这些因素提供了一些见解。每个配位几何的人口被发现很大程度上取决于丁酰胺取代基的区域化学。不同寻常的是，对于dota -四酰胺配合物，观察到早期镧系元素通常倾向于扭曲的方形反棱镜配位几何，而后期镧系离子也越来越倾向于这种配位几何。这与简单的dota -四酰胺复合物如DOTAM形成鲜明对比。酰胺丁基取代基体积越大，提供电子越多，这种效应就越普遍。它还与后来采用扭曲方形反棱镜几何结构的镧系元素配合物中球内水分子的损失有关。具有仲丁基取代基的配合物由于在每个垂臂上引入了立体化学中心，因此本身就比较复杂。与具有较大酰胺取代基的手性配合物不同，这些配合物的垂臂取向没有“锁定”效应，最多可观察到四种非对映异构体配位异构体。
The coordination geometry adopted by the lanthanide complexes of DOTA-tetraamides is a critical factor in determining their water exchange kinetics. Controlling the water exchange kinetics of DOTA-tetraamide complexes, and by extension their coordination geometry, is of particular interest because of the potential application of this class of complex as PARACEST MRI contrast agents. In order to facilitate the maximum CEST effect at the lowest pre-saturation powers much slower exchange kinetics are required than are commonly observed with these types of complex. Complexes that adopt the more slowly exchanging square antiprismatic coordination geometry are therefore preferred; however, the factors that govern which coordination geometry is preferred remain unclear. A series of DOTA-tetraamide complexes with butyl amide substituents in different regioisomeric configurations provides some insight into these factors. The population of each coordination geometry was found to vary substantially depending upon the regiochemistry of the butyl amide substituent. Unusually for DOTA-tetraamide complexes it was observed that the twisted square antiprismatic coordination geometry, usually favoured by early lanthanides, is also increasingly favoured by the later lanthanide ions. This is in marked contrast to simple DOTA-tetraamide complexes such as DOTAM. This effect becomes more prevalent the more bulky and more electron donating the amide butyl substituents become. It is also associated with loss of an inner-sphere water molecule from the complexes of later lanthanides that adopt the twisted square antiprismatic geometry. The complexes with sec-butyl substituents are inherently more complicated because of the introduction of a stereochemical centre into each pendant arm. Unlike chiral complexes with larger amide substituents there is no ‘locking’ effect of the orientation of the pendant arms in these complexes and up to four diastereoisomeric coordination isomers can be observed.
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影响因子：
3.5
作者：
Suchy, Mojmir;Li, Alex X.;Hudson, Robert H. E.
通讯作者：
Hudson, Robert H. E.
影响因子：
2.7
作者：
Faulkner, S;Beeby, A;Williams, JAG
通讯作者：
Williams, JAG
影响因子：
4
作者：
Dickins, RS;Batsanov, AS;Salamano, S
通讯作者：
Salamano, S
影响因子：
2.6
作者：
Gunnlaugsson, T;Davies, RJH;Mulready, S
通讯作者：
Mulready, S
DOI：
10.1002/cber.19931260404
发表时间：
1993-04-01
期刊：
CHEMISCHE BERICHTE-RECUEIL
影响因子：
--
作者：
HOEFT, S;ROTH, K
通讯作者：
ROTH, K