Herein we describe the synthesis and characterization of new sulfonated and carboxylated poly(propyleneimino) (PPI) dendrimers with the ethylenediamino (EDA) core, at generations 1, 2 and 3. By means of UV-Vis and EPR spectroscopy, using Cu2+ as a probe, we concluded that these dendrimers show a specific pattern in the coordination of metal ions. In agreement with the UV-Vis studies, EPR spectra of carboxylated compounds are constituted by 3 different signals which appear and then disappear with increasing copper concentration, corresponding to the saturation of different copper complexation sites. At the lowest copper concentration up to a 1 : 1 molar ratio between CuII and the dendrimer, the spectrum is characteristic of a CuN2O2 coordination at the core of the dendrimer. The spectrum appearing at higher CuII concentrations indicates a peripheral location of the ions coordinating one nitrogen and 3 oxygen atoms in a square planar geometry in restricted mobility conditions. For the highest concentrations tested, copper ions are confined at the external dendrimer surface with CuO4 coordination. For sulfonate systems, the EPR results are in line with a weaker interaction of CuII with the nitrogen sites and a stronger interaction with the oxygen (SO3−) groups with respect to the interactions measured by EPR for carboxylate systems.
本文中,我们描述了具有
乙二胺(E
DA)核心的新型
磺酸化和
羧酸化的聚(
丙烯亚胺)(P
PI)树枝状大分子的合成与表征,涉及1代、2代和3代。通过使用Cu$^2+}$作为探针的UV-Vis和EPR光谱学手段,我们得出结论,这些树枝状大分子在
金属离子的配位上显示出特定的模式。与UV-Vis研究一致,
羧酸化化合物的EPR光谱由3种不同信号组成,这些信号随着
铜浓度的增加出现并随后消失,对应于不同
铜配位位点的饱和。在
铜浓度最低至1:1的Cu$^2+}$与树枝状大分子摩尔比时,光谱特征为树枝状大分子核心的CuN2O2配位。在较高Cu$^2+}$浓度下出现的光谱表明,离子在外周位置配位,以四边形平面几何结构在一个氮和三个氧原子进行配位,处于受限运动条件。对于所测试的最高浓度,
铜离子被限制在树枝状大分子的外表面,具有
CuO4配位。对于
磺酸盐系统,EPR结果表明,与氮位点的Cu$^2+}$相互作用较弱,与氧(SO3$^-$)位点的相互作用较强,相较于通过EPR测量的
羧酸盐系统的相互作用。