Abstract

We herein report the synthesis of novel “Janus” calix[4]arenes bearing four “molecular tethering” functional groups on either the upper or lower rims of the calixarene. These enable facile multipoint covalent attachment to electrode surfaces with monolayer coverage. The other rim of the calixarenes bear either four azide or four ethynyl functional groups, which are easily modified by the copper(I)-catalyzed azide–alkyne cycloaddition reaction (CuAAC), either pre- or postsurface modification, enabling these conical, nanocavity reactor sites to be decorated with a wide range of substrates to impart desired chemical properties. Redox active species decorating the peripheral rim are shown to be electrically connected by the calixarene to the electrode surface in either “up” or “down” orientations of the calixarene.

Highlights

  • Heterogeneous support of surface-immobilized species can provide several advantages over homogeneous systems, such as being reusable, nonleaching, and nonintrusive to the systems they are employed within

  • Given the enormous scope of substrates that are amenable to this approach, in this report we are focused on presenting the synthesis, characterization, and multipoint, robust, electrode surface modification of four different Janus calixarenes attached to the surface using two different strategies and each bearing four identical functional groups on either upper or lower rims comprising of (i) organic nitro functionalities; (ii) organometallic azide-functionalized ferrocenyl moieties; (iii) ethynylfunctionalized ferrocenyl groups; (iv) organic 1-ethynyl-3,5bis(trifluoromethyl)benzene moieties

  • Once bound to the glassy carbon electrode (GCE) surface, the exposed face of the calixarene was designed for facile modification using the copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction

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Summary

■ INTRODUCTION

Heterogeneous support of surface-immobilized species can provide several advantages over homogeneous systems, such as being reusable, nonleaching, and nonintrusive to the systems they are employed within. Having selected two complementary and widely applicable surface attachment strategies, we were only left with the question of how to attach the target modifying molecules to the calixarene in a way that is applicable for a wide a range of different substrates To this end, we report methods to functionalize either the upper or lower rim of calix[4]arenes, the rim not used for attachment to the surface with either azide or ethynyl moieties. Given the enormous scope of substrates that are amenable to this approach, in this report we are focused on presenting the synthesis, characterization, and multipoint, robust, electrode surface modification of four different Janus calixarenes attached to the surface using two different strategies and each bearing four identical functional groups on either upper or lower rims comprising of (i) organic nitro functionalities; (ii) organometallic azide-functionalized ferrocenyl moieties; (iii) ethynylfunctionalized ferrocenyl groups; (iv) organic 1-ethynyl-3,5bis(trifluoromethyl)benzene moieties. Aside from presenting synthetic routes to novel functionalized calix[4]arenes, including the first examples of tetraazido (upper rim) functionalized calix[4]arenes, this report seeks to demonstrate widespread applicability in providing a facile method of covalently attaching more than one species through more than one bond to a surface proffered by the use of Janus calixarenes

■ RESULTS AND DISCUSSION
■ CONCLUSION
■ ACKNOWLEDGMENTS
■ REFERENCES
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