Correspondence on "Confinement of Polyiodides by Dual-Functional Tetrazine Cathodes in Zn-I₂ Batteries"

In a recent research article (doi.org/10.1002/anie.202507497), Chi, Huang, Qu et al. described a multifunctional cathode for Zn-I₂ batteries based on a s-tetrazine ligand bearing two morpholine pendants, forming the active 2I₃ ^-@BMT complex. In addition to the lack of proper attribution for prior reports by other authors (doi.org/10.1021/acs.inorgchem.6b01138; doi.org/10.1039/c7dt00134g) regarding the design of this ligand as an anion receptor, its synthesis and its ability to form triiodide complexes, the article is affected by serious scientific/technical flaws. The actual composition of the 2I₃ ^-@BMT complex was not established, and protonation of morpholine groups in aqueous media, essential to the formation of the triiodide complex, was overlooked, despite prior studies and crystallographic evidence. The 2:1 I₃ ^-:BMT ratio was investigated in chloroform using a Job plot, while a 1:1 stability constant was determined via UV-vis titration in the same solvent. Both methods raise concerns, their results lack consistency and the extrapolation of data from chloroform to aqueous systems is not justified. Additionally, theoretical calculations yielded a highly positive binding energy, erroneously interpreted as indicative of complex stability, and a questionable complex structure featuring unconvincingly short anion-tetrazine contacts. Nevertheless, functioning of reported cathode for Zn-I₂ batteries is a notable outcome of the study.