Anionic sulfonated and carboxylated PPI dendrimers with the EDA core: synthesis and characterization of selective metal complexing agents

Abstract

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 Cu(2+) 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 Cu(II) and the dendrimer, the spectrum is characteristic of a CuN2O2 coordination at the core of the dendrimer. The spectrum appearing at higher Cu(II) 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 Cu(II) with the nitrogen sites and a stronger interaction with the oxygen (SO3(-)) groups with respect to the interactions measured by EPR for carboxylate systems.

Dendronized Anionic Gold Nanoparticles: Synthesis, Characterization, and Antiviral Activity

“…We have to consider that gold has a high affinity for sulfur, and these dendrons contain other sulfur atoms in their scaffold, apart from that of the focal point. Additionally, the anionic system S(CH 2 ) 3 SO 3 − can act as a chelating agent . Thus, to minimize the trapping ability of these outer groups, we decreased the gold/dendron ratio in the reaction by using the number of sulfonate groups of the wedge as a reference.…”

“…For example, sulfonate thioether–carbosilane dendrimers have been used to stabilize AgNPs . We previously studied the ability of peripheral sulfonate groups to coordinate Cu II cations in anionic carbosilane dendrimers by EPR spectroscopy; the coordination mode is dependent upon the SO 3 − /Cu II molar ratio . With this in mind, and with the aim of confirming the type of interaction between the gold surface and dendrons, we investigated dendrons 4 – 6 and NPs 7 a and 7 b – 9 b by means of computer‐aided analysis of the EPR spectra obtained by adding increasing amounts of Cu II with respect to a fixed amount of sulfonate groups (0.01 m ).…”

“…The parameters reported in Table were compared with other magnetic parameters reported in the literature for similar copper(II) complexes to identify the structure and coordination of the dendron complexes . All signals correspond to quite distorted square‐planar copper(II) coordination environments.…”

“…Additionally,t he anionic system S(CH 2 ) 3 SO 3 À can act as ac helating agent. [56,57] Thus, to minimize the trapping ability of these outer groups,w edecreasedt he gold/dendron ratio in the reaction by using the number of sulfonate groups of the wedge as ar eference. Hence, the new gold/dendron ratios for the reaction were 2:1 for 4,4 :1 for 5,a nd 8:1f or 6.W ith these considerations in mind, the same procedure as that described above was successful, rendering water-soluble AuNPs for the three dendrons (Scheme2;A u@(SG n (SO 3 À ) m ); n = 1, m = 2( 7b); n = 2, m = 4 (8b); n = 3, m = 8( 9b)).…”

“…[68] We previously studied the ability of peripheral sulfonate groups to coordinate Cu II cations in anionic carbosilane dendrimers by EPR spectroscopy;t he coordination mode is dependentu pon the SO 3 À /Cu II molar ratio. [56,57] With this in mind, and with the aim of confirmingt he type of interaction between the gold surface and dendrons, we investigated dendrons 4-6 and NPs 7a and 7b-9b by means of computer-aideda nalysiso ft he EPR spectra obtainedb ya dding increasing amountso fC u II with respect to afixed amount of sulfonate groups (0.01 m). Control spectra, obtainedb yt aking ac onstantc opper(II) concentration and changing the nanocomposite concentration, showedt hat the spectra were almost comparable at the same Cu II /SO 3 À group molar ratio;t herefore, this is the most relevant parameter in the system.…”