Alkyne-azide Cycloaddition Catalyzed By Self-assembly Films Of Cu(â…¡) Complex Of Phenanthroline Derivatives

“Click chemistry” has emerged as a fast and efficient approach to synthesis of novel compounds with desired functions. The copper catalyzed alkyne-azide cycloaddition(Cu AAC) to afford 1, 2, 3-triazoles ring system is one of the most prominent click reactions. The use of homogeneous catalyst could be costly and uneconomical in large scale due to the complicated recovery process. Immobilizing Cu ion on a solid supporter can solve this problem to some extent. In this paper,phenanthroline derivative ligands L1 and L2 were synthesized and characterized by1 H NMR, IR and MS. Their self-assembly monolayer and layer-by-layer assembly multilayers on hydrophilic substrate were prepared by “bottom-up” method and were characterized by WCA, UV-vis, AFM, XPS and ICP-AES. The catalytic properties of the self-assembled films were studied and the catalytic mechanism of Cu AAC reaction in heterogeneous system was proposed preliminarily. Specific content as follows:1. Synthesis of Phenanthroline derivatives ligands.(Scheme 1)2. Synthetic route of self-assembly monolayers of Cu(Ⅱ) complex of phenanthroline derivative.(Scheme 2)3. Synthetic route of layer-by-layer assembly multilayers of Cu(Ⅱ) complex of phenanthroline derivative.(Scheme 3)4. Cu AAC reaction catalyzed by self-assembled films of Cu(Ⅱ) complex of phenanthroline derivatives was investigated. The results showed as follow: 1) These self-assembly films had a high activity(TON up to 11550) which was better than that observed in homogeneous environment and could be reused from three to seven times.2) Effect of the number of layers of the self-assembly films on its catalytic properties were also systematic investigated. Both the amount of copper element and the catalytic activity increased along with the increasing number of layers. When assembled to three layers, the loading of the copper element reached the limit as well as the catalytic activity due to the steric hindrance of the catalyst. The catalyst supported on the surface of the glass substrate were easy to be recovered compared to conventional supported catalyst without filtering or other complex operations.5. The catalytic reaction mechanism was initially explored by XPS analysis,which indicated that catalytic process mainly occurred on the surface of the film and rationalized that the Cu(Ⅰ) species reduced from the Cu(Ⅱ) catalyst were active species.