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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Dynamic NMR properties of DOTAligand:variable pH and temperature ~1H NMR study on [K(H_xDOTA)]~(3-x)-species
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Dynamic NMR properties of DOTAligand:variable pH and temperature ~1H NMR study on [K(H_xDOTA)]~(3-x)-species

机译：DOTA配体的动态NMR特性：[K（H_xDOTA）]〜（3-x）-物种的pH和温度〜1H NMR可变研究

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The 'H NMR spectra of [H_xDOTA]~(4-x)-species are reported as a function of pH and temperature in aqueous solution.The spectra show line broadening both in ligand proton signals and also in the water proton signal by titration with KOH solution.The formation of different [K(H_xDOTA)]~(3-x)-complexes is found to be responsible for this behaviour.At high pH the usual fluxional motions,i.e.the ring inversion and the change in the acetate arms' helicity,which are also characteristic for other but inert metal-DOTA complexes,have been detected.However,because of the kinetic lability of K~+-O and K~+-N coordinative bonds a new type of rearrangement appears.This new motion requires breaking of coordinative bonds in the complex and can be described as a certain type of "ring slewing" around the ring C-C bonds.At low temperature(about 270 K)the ring slewing slows down and becomes negligible compared with the ring inversion and the change in the arms' helicity.These two latter processes have the same rate.When the temperature is higher(about 320 K)the ring slewing accelerates and its rate exceeds the rate of ring inversion.At this temperature the change in the acetate arms' helicity has the same rate as the ring slewing.Additionally,in the pH range 4-5 a slow intermolecular proton exchange process has been observed between the water and the dissociable protons of [K(H_xDOTA)]~(3-x)-.A water-assisted proton exchange mechanism is proposed on the basis of the activation parameters.This finding supports the previously suggested slow proton motion hypothesis for the formation of DOTA complexes.
机译：据报道[H_xDOTA]〜（4-x）物种的1 H NMR谱图是水溶液中pH和温度的函数。谱图显示，通过用滴定法在配体质子信号和水质子信号中都加宽了谱线KOH溶液。发现不同的[K（H_xDOTA）]〜（3-x）络合物的形成是这种行为的原因。在高pH下，通常的通量运动，即环反转和乙酸酯臂的变化。已经检测到螺旋度，这对于其他但惰性的金属-DOTA配合物也具有特征。但是，由于K〜+ -O和K〜+ -N配位键的动力学不稳定性，出现了一种新型的重排。需要打破配合物中的配位键，并且可以描述为环CC键周围的某种类型的“环回转”。在低温（约270 K）下，环回转的速度变慢并且与环反转和环跃变相比可以忽略不计。武器螺旋度的变化。后两个过程具有当温度较高时（约320 K），环回转加速，并且其速率超过环反转的速率。在此温度下，乙酸酯臂螺旋度的变化与环回转的速率相同。在pH值4-5范围内，观察到水与[K（H_xDOTA）]〜（3-x）-的可解离质子之间的分子间质子交换过程缓慢。该发现支持了先前提出的用于形成DOTA复合物的慢质子运动假说。

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