Visible‐Light‐Active Mixed‐Valent Copper‐Ion‐Coordinated 2,5‐Dimercapto‐1,3,4‐thiadiazole‐Based p‐Type Metallopolymer

Abstract

Visible‐light‐active coordination metallopolymer and metal‐organic frameworks have gained substantial attention in recent years, owing to their tunable electronic properties. Herein, we present a novel copper‐ion‐containing metallopolymer, which exhibits visible‐light absorption and p‐type photoelectrochemical behavior. The functional thiadiazole‐based metallopolymer thin films were prepared by using both chemical and electrochemical methods on fluorine‐doped tin oxide substrates. XPS, Raman, and FTIR spectral investigations evidence the presence of Cu(II), Cu(I), Cu−S, and disulfide (S−S)2− linkages in the polymeric network. The swift photoresponses, repeatable photovoltage of approximately 55 mV with zero applied current, and high photocurrent values at different bias potentials (ca. 24 μA cm−2 @ −0.6 V vs. Ag/AgCl in 0.1 KCl) in acidic electrolytes (0.5 M H2SO4) suggest that this metallopolymer as an acid‐stable p‐type photocathode material. In contrast, the electropolymerized non‐metallated polymers exhibit n‐type photoactivity. Photoelectrochemical sensing studies reveal the analyte‐induced reduction in photoactivity.

Visible-Light-Active Triazine–Thiadiazole-Based p-Type Copolymer with Stable Photoelectrochemical Behavior in Acidic Electrolytes

“…Triazine trichloride (CC) being a well-known planar building block of carbon nitride can readily undergo nucleophilic substitution by replacement of all chloro units. , This is very valuable in building porous 2D, 3D organic frameworks, dendritic polymeric structures under mild reaction conditions with N-, O-, S-containing nucleophiles . In our present study, the CC dissolved in acetonitrile (0.005 M) was gradually added to react with the functional thiadiazole monomers (K 2 DMcT0.02 M) in 20 mL of 0.5 M Na 2 SO 4 solution under constant stirring to obtain the deep yellowish-orange-colored triazine-thiadiazole copolymer, shown along with Scheme .…”

“…This illustrates the facile replacement of chloro units of CC with the bridging DMcT thio units. Moreover, dimercaptothiadiazole is a good bridging ligand in forming coordination metallopolymeric structures. , As the concentration of CC to DMcT was increased, the extent linkages with the planar triazine units could result in larger network polymeric structures. The electron-rich characteristic of the DMcT unit and its higher solubility as a salt solution enhance the reaction with electron-deficient triazine by nucleophilic substitution.…”

Proton-Coupled Electron Transfer on Mixed-Valent Copper Ions Containing S- and N-Rich Triazine-Dimercapto Thiadiazole Coordination Polymer Photocathodes

“…In addition, the nonmetalated poly­(Cu-DMcT) exhibits relatively lower photocurrent values compared to poly-Cu-DMcT-CC. In contrast, the metal-free poly­(dimercapto thiadiazole) and poly­(triazine trithiolate) polymer show n-type behavior with relatively low photocurrent values in the range of 40–60 nA cm –2 . − Furthermore, the incorporation of redox-active metal ions into the DMcT-CC metallopolymeric coordination network is under detailed investigation to improve the photoredox activity in m-PCET reactions. The extended conjugation, modulation of local coordination, and electronic structures with other photoredox active metal ions could play a crucial role in the improvement of the photoelectrochemical activity in m-PCET reactions.…”

Bismuth(III) Coordination Linkage with Dimercaptothiadiazole: A p-Type Metallopolymer Photocathode Stable in Protic Electrolytes

“…Hence, various efforts were made in search of efficient hole/electron transporting materials that can form heterostructures with photoactive metal–organic polymers. This facilitates improving the photoexcitons' charge separation and the interfacial photoelectrochemical stability as an overlayer on the inorganic semiconductors. , …”

“…Recently, coordination molecular complexes, metal–organic polymers, and metallo-organic frameworks have been widely investigated for diverse applications due to their tunable structural and electronic properties. , The coordination structures with two- and three-dimensional networks could provide an efficient charge transfer from metals to ligands and vice versa and utilize the photoredox activity. ,, Notably, the charge trapping and recombination of photogenerated excitons can be minimized while using metal-incorporated coordination polymers. ,,, Recently, functional organic ligands with linker units have been explored for the development of photoactive coordination molecular systems. ,,, Metal ions incorporated with highly functionalized ligands have been explored for various applications. − Especially, the proton relay sites at ligands which are structurally positioned in the secondary coordination sphere of the redox-active metal centers could favor multiple proton–electron transfer in electrocatalytic reactions. , This enables the fast transfer or exchange of protons to the local redox-active sites, which is essential for m-PCET. The polydentate functional ligand systems that are rich in N and S in the backbone have obtained interest in coordination photoelectrocatalysts. ,− In our previous reports, triazine trithiolate and dimercaptothiadiazole being the functional ligands can form highly cross-linked coordination network structures and provide good charge transport. ,, …”