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Reversible photoreduction of Cu(II)-coumarin metal-organic polyhedra

Reversible photoreduction of Cu(II)-coumarin metal-organic polyhedra
Jaeyeon Bae
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Bae, Jaeyeon; Park, JinheeKim, Hyun-Chul
Hyun-Chul Kim
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As a novel class of inorganic-organic hybrid materials, metal-organic polyhedra (MOPs) are discrete cage-like supramolecules that consist of organic linkers coordinated to metal ions or metal clusters by self-assembly. In the recent decades, MOPs have been tremendously studied owing to their designability, tailora-bility, solubility and intrinsic porosity through choosing metal sources and designing organic ligands. In addition, MOPs have been applied to several applications such as guest molecule storage, separation, cataly-sis, drug delivery, sensing. In order to develop the functional MOP materials for application, the various techniques have been widely studied such as post-synthetic modification, direct self-assembly, assembly with other materials. We report a new post-synthetic modification for controlled photoinduced reduction of Cu(II) in MOPs that will be a valuable contributor to the development of Cu+/Cu0-based catalysts. To realize controlled Cu2+ reduction, coumarin as a triplet quencher of excited benzophenone was tethered to Cu(II)-metal-organic pol-yhedra (MOPs). In addition, coumarin functionalized MOPs stabilized Cu+ state which has high reduction potential through perturbing the direct electron transfer from benzophenone to Cu paddlewheel clusters by quenching. Moreover, the Cu2+ to Cu+ reduction was reversible by alternating UV irradiation and O2 expo-sure because coumarin groups allowed the MOPs to be soluble in optimized solvent. The photoinduced cata-lytic activity of the coumarin-MOPs was also examined in a Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC).
Table Of Contents
I. INTRODUCTION 1 II. EXPERIMENT METHOD & MATERIALS 3 2.1 Materials 3 2.2 Measurements 3 2.3 Synthesis of Organic Ligands 4 2.3.1 Synthesis of L1 4 2.3.2 Synthesis of L2 5 2.3.3 Synthesis of L3 7 2.4 Synthesis of Metal-Organic Polyhedra 8 2.4.1 Synthesis of Coumarin-MOP-1 8 2.4.2 Synthesis of Coumarin-MOP-2 8 2.4.3 Synthesis of Coumarin-MOP-3 9 2.5 Reduction Study of Coumarin-MOPs 9 2.5.1 Reduction Study of Coumarin-MOP-1 9 2.5.2 Reduction Study of Cousmrin-MOP-2 9 2.5.3 Reduction Study of Coumarin-MOP-3 9 2.6 Reversible Cu2+ to Cu+ Reduction Process 10 2.6.1 Reversible Cu2+ to Cu+ Reduction Process of Couamrin-MOP-1 10 2.6.2 Reversible Cu2+ to Cu+ Reduction Process of Couamrin-MOP-2 10 2.6.3Reversible Cu2+ to Cu+ Reduction Process of Couamrin-MOP-3 11 2.7 Control Experiments for UV Irradiation 11 2.7.1 UV Irradiation of Cu(NO3)2 11 2.7.2 UV Irradiation of Cu(CH3COO)2 11 2.7.3 UV Irradiation of MOP-4 11 2.7.4 UV Irradiation of L1 12 2.7.5 UV Irradiation of Benzophenone 12 2.7.6 UV Irradiation of L1 + Benzophenone 12 2.8 Copper Catalyzed Azide-Alkyne Cycloaddition (CuAAC) 13 2.8.1 Catalytic Activity Test with Click Reaction of Coumarin-MOP-1 13 2.8.2 Catalytic Activity Test with Click Reaction of Cu+ Sources 13 III. RESULT AND DISCUSSION 14 3.1 Design of Ligands and MOPs 14 3.2 Photoinduced Reduction System 19 3.2.1 Proposed Mechanism 19 3.3 Photoinduced Reduction Rate 20 3.4 Control Experiments 25 3.5 Reversible Reduction Experiments 27 3.6 Catalytic Activity Experiments 31 IV. CONCLUSIONS 33 V. REFERENCES 34 VI SUMMERY 37
Emerging Materials Science
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