Sonochemically-Promoted Preparation of Silica-Anchored Cyclodextrin Derivatives for Efficient Copper Catalysis.

Katia Martina,Rafael Luque,Alessio Zuliani,Giancarlo Cravotto,Fernando Chávez-Rivas,Federica Calsolaro,Maria Jesus Moran,Gloria Berlier

doi:10.3390/molecules24132490

Abstract

Silica-supported metallic species have emerged as valuable green-chemistry catalysts because their high efficiency enables a wide range of applications, even at industrial scales. As a consequence, the preparation of these systems needs to be finely controlled in order to achieve the desired activity. The present work presents a detailed investigation of an ultrasound-promoted synthetic protocol for the grafting of β-cyclodextrin (β-CD) onto silica. Truly, ultrasound irradiation has emerged as a fast technique for promoting efficient derivatization of a silica surface with organic moieties at low temperature. Three different β-CD silica-grafted derivatives have been obtained, and the ability of β-CD to direct and bind Cu when CD is bonded to silica has been studied. A detailed characterization has been performed using TGA, phenolphthalein titration, FT-IR, diffuse reflectance (DR), DR UV-Vis, as well as the inductively-coupled plasma (ICP) of the β-CD silica-grafted systems and the relative Cu-supported catalysts. Spectroscopic characterization monitored the different steps of the reaction, highlighting qualitative differences in the properties of amino-derivatized precursors and final products. In order to ensure that the Cu-β-CD silica catalyst is efficient and robust, its applicability in Cu(II)-catalyzed alkyne azide reactions in the absence of a reducing agent has been explored. The presence of β-CD and an amino spacer has been shown to be crucial for the reactivity of Cu(II), when supported.

Highlights

The design of novel organic-inorganic hybrid systems has achieved considerable success in several fields, including catalysis, photochemistry, biochemistry, and optoelectronics [1]
Β-CD was anchored to silica via a diethylentriamino spacer that can contribute to Cu binding strength, and amino CD was directly grafted onto the silica surface (Scheme 1)
The sample was characterized by medium particle size, in the range of tenths to hundredths of micrometers, formed by the agglomeration of nanosized (20–50 nm) primary particles

Summary

Introduction

The design of novel organic-inorganic hybrid systems has achieved considerable success in several fields, including catalysis, photochemistry, biochemistry, and optoelectronics [1]. A hybrid inorganic-organic, TiS2 , and ammonium-cation-based superlattice has recently been described as a promising flexible thermoelectric thin film [6]. 22of of 18 tailorable dielectric properties [7]. The key feature of this type of system is that its characteristics arise properties [7]. The key featurecontributions of this type ofofsystem is thatbut its characteristics arise from the from the individual the phases, from the properties of the inner individual contributions of the phases, and from the properties of the inner interface, which can interface, which can be predominant. The unique active behavior of these hybrid systems is be predominant

Methods

Results

Conclusion