Electrofluorochromism of Surface-Confined Tetrazines Investigated on the Monolayer Scale

Abstract

Monolayers of tetrazine terminated alkyl chains have been grafted on ITO through siloxane functions. These monolayers are electroactive and display fluorescence with a maximum close to 560 nm when excited in the visible range. Potential step cycles have been applied and the fluorescence intensity drawn from background and bleaching corrected emission spectra was found to be switched off and on reversibly according to the applied potential. This demonstrates that the luminescence of grafted fluorophores can be electrochemically controlled as it is in solution and the emission intensity can be followed with a good signal to noise ratio even for a monolayer.

Survey of Recent Advances in Molecular Fluorophores, Unconjugated Polymers, and Emerging Functional Materials Designed for Electrofluorochromic Use

“…An advantage offered by these heterocyclic aromatics is their electron deficiency, which allows them to be electrochemically reduced. This was exploited by Guerret-Legras et al who developed monolayers of the tetrazine F2 ( Figure 8 ) [ 88 ]. This was achieved by covalently bonding a coating of the fluorophore to ITO-coated glass via a triethoxy siloxane linker.…”

“… Representative examples of consolidated intrinsically electroactive organic fluorophores used as EFC materials [ 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 ]. …”

Siloxanes—Versatile Materials for Surface Functionalisation and Graft Copolymers

“…A triethoxysilane-functionalised tetrazine derivative was grafted onto the surface of indium-tin oxide (ITO) electrodes via immersing the electrodes in a solution of this derivative that also contained acetic acid ( Figure 4 ) [ 1 ]. Although no mechanism is mentioned, the authors have likely relied on the presence of hydroxyl groups on the ITO surface and their reaction with the silane-functionalised tetrazine to form siloxane bonds for modifying the electrodes.…”

“…The Si-O bond is a highly versatile chemical linkage that can be found in a great variety of materials and molecules, linking together inorganic [ 1 , 2 , 3 ] and organic species [ 4 , 5 , 6 ], as well as being a building block for polymers [ 7 , 8 , 9 ] and sophisticated 3D oligomers [ 10 , 11 ]. In the role of linkage, the siloxane bond is robust, chemically resistant to an array of environments and easily established, e.g., via the reaction of silanes with organic or inorganic hydroxyl groups [ 6 , 12 , 13 ].…”

Synthesis of tetrazine-tetracyanobutadienes and their transformation into pyridazines via inverse-electron demand Diels–Alder cycloaddition (IEDDA)

“…1 Tetrazine-based systems are particularly appealing due to (1) the ability of the core nitrogen atoms to coordinate and thus form metal complexes, 2,3 (2) the fact that they are high energy materials because of the high nitrogen content, 4 (3) their participation in inverse-electron demand Diels-Alder cycloaddition (IEDDA) reactions, 5 and (4) a unique n-π* electronic transition allowing visible light absorption and rendering of deep red colour materials. 1 Thus, tetrazine derivatives have potential applications in organic electronics, 6 electrofluorochromism, 7 coordination chemistry, 8 energetic materials, 9 and fluorescence sensing. 10 Banking on the intriguing properties of tetrazine, a wide variety of molecules have been developed and their applicability in various fields has been explored.…”