The Coordination State of Copper(II) Complexes Anchored and Grafted onto the Surface of Organically Modified Silicates

Abstract

Amine derivatives of alkoxides such as (3-aminopropyl)trimethoxysilane and (3-(2-aminoethyl)aminopropyl)trimethoxysilane are reagents in the sol−gel process and, at the same time, versatile ligands forming complexes with transition metal ions (e.g., Cu(II)). One of the major advantages of the sol−gel process is the possibility of preparing Cu(II) complexes in the interior of and on the surface of organically modified silicate xerogels. This paper compares Cu(II) complexes prepared in the interior of silica xerogels with those grafted and anchored onto the surface of such xerogels. Grafting and anchoring require prior preparation of supports with functionalized surfaces. In the former process Cu(II) ions are chemisorbed, and in the latter Cu(II) complexes are immobilized by a condensation reaction. The following spectroscopic results are presented: FT-IR, optical absorption in the visible region, and electron paramagnetic resonance (EPR). The EPR studies are summarized in three identified models of the coordination sites on the modified silica xerogel surfaces. The materials studied are put forward as catalyst precursors.

Exceptional Affinity of Nanostructured Organic–Inorganic Hybrid Materials towards Dioxygen: Confinement Effect of Copper Complexes

“…Moreover, these nanostructured materials can be prepared by incorporating many different organic chelates and complexes into the framework. [32][33][34][35][36][37][38][39][40][41] Finally, increased stability of the immobilized complexes within the material is expected when compared to the isolated units.…”

Mesoporous Silica Functionalized by Cyclam–Metal Groups: Spectroscopic Studies and Numerical Modeling

“…Thus, the considered materials are the subject of broad field of investigations [9][10][11][12] since the functionalities can be tuned by changing the nature of the functional groups such as nanoparticles [13], magnetic clusters [14], organic or organometallic molecules [15]. Besides, these materials can be prepared by incorporating several classes of organic chelates depending on the targeted property [16][17][18][19]. In this aim, the development of different synthesis routes was extensively experienced and applied to silica backbone on the form of mesoporous materials with pore sizes ranging from 2 to 20 nm.…”

New Pb2+ carbon paste electrode based on organically modified silicate and its square wave anodic stripping voltammetric response for pretreated gasoline samples

“…The characteristic Si-O-Si bands at 1200, 1079, 948 e 791 and 465 cm -1 are related with the condensed silica network and it can be seen at both spectra. [14][15][16][17] In Figure 1b, a weak band at 695 cm -1 attributed to the N-H stretching mode confirms incorporation of amino group to the silica network. [15][16][17] Another absorption band at 1530 cm -1 , which can be assigned to the symmetric -NH 3 + bending vibration is observed due a part of amino group to be protonated by residual silanol groups during synthesis of hybrid material.…”

“…[14][15][16][17] In Figure 1b, a weak band at 695 cm -1 attributed to the N-H stretching mode confirms incorporation of amino group to the silica network. [15][16][17] Another absorption band at 1530 cm -1 , which can be assigned to the symmetric -NH 3 + bending vibration is observed due a part of amino group to be protonated by residual silanol groups during synthesis of hybrid material. 18 A very weak intensity band at 1408 cm -1 is ascribed to the deformation mode of COO -produced from reaction between CO 2 present in air and aminopropil group on silica matrix.…”

“…16 Still in Figure 1b, in the higher frequency region, the presence of aminopropil groups was corroborated by presence of two weak bands at 2821 and 2901cm -1 attributed to the symmetric and asymmetric stretching vibrations of -CH 2 and -CH 3 groups, respectively. 15,17 There is a weak absorption band around 3290 cm -1 which appears as a small shoulder superimposed with a broad side band, which can be attributed to the stretching vibration mode of NH 2 groups. 16,17 The infrared spectrum of the APSil is consistent with the spectrum of the similar material reported in the literature.…”