Salts bearing the tetracyanopyrrolide anion (TCP) were synthesized from tetracyano‐1,4‐dithiin and sodium azide according to a modified synthetic protocol. The solid‐state structures of HTCP, MeTCP, Me4NTCP, NaTCP, and the ionic liquid EMIMTCP (EMIM = 1‐ethyl‐3‐methylimidazolium) are discussed for the first time. According to experimental and computational data, the TCP anion can be regarded as a pseudohalide with π bonds highly delocalized over the entire anion including the four cyano groups. The planar anion is C2v symmetric and represents a multifunctional binary CN ligand, which is capable of forming classic coordination bonds through the lone pairs of the CN groups or the ring nitrogen atom. In addition, noncovalent interactions such as π–π interactions are found and can be used to strengthen structural and electronic communication between organic ligands.

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Recently, we reported on a series of aminomethylene-phosphonate (AMP) analogues, bearing one or two heterocyclic groups on the aminomethylene moiety, as promising Zn(II) chelators. Given the strong Zn(II) binding properties of these compounds, they may find useful applications in metal chelation therapy. With a goal of inhibiting the devastating oxidative damage caused by prion protein in prion diseases, we explored the most promising ligand, {bis[(1H-imidazol-4yl)methyl]amino}methylphosphonic acid, AMP-(Im) 2 , 4, as an inhibitor of the oxidative reactivity associated with the Cu(II) complex of prion peptide fragment 84−114. Specifically, we first characterized the Cu(II) complex with AMP-(Im) 2 by ultraviolet−visible spectroscopy and electrochemical measurements that indicated the high chemical and electrochemical stability of the complex. Potentiometric pH titration provided evidence of the formation of a stable 1:1 [Cu(II)-AMP-(Im) 2 ] + complex (ML), with successive binding of a second AMP-(Im) 2 molecule yielding ML 2 complex [Cu(II)-(AMP-(Im) 2 ) 2 ] + (log K′ = 15.55), and log β′ = 19.84 for ML 2 complex. The CuN3O1 ML complex was demonstrated by X-ray crystallography, indicating the thermodynamically stable square pyramidal complex. Chelation of Cu(II) by 4 significantly reduced the oxidation potential of the former. CuCl 2 and the 1:2 Cu:AMP-(Im) 2 complex showed one-electron redox of Cu(II)/Cu(I) at 0.13 and −0.35 V, respectively. Indeed, 4 was found to be a potent antioxidant that at a 1:1:1 AMP-(Im) 2 :Cu(II)-PrP 84−114 molar ratio almost totally inhibited the oxidation reaction of 4-methylcatechol. Circular dichroism data suggest that this antioxidant activity is due to formation of a ternary, redox inactive Cu(II)-Prp 84−114 -[AMP-(Im) 2 ] complex. Future studies in prion disease animal models are warranted to assess the potential of 4 to inhibit the devastating oxidative damage caused by PrP.

Hevroni designed, synthesized, and supplied the major compound investigated in our joint paper. Her name was originally on the author list but then was omitted by mistake. Unfortunately, we did not notice this mistake until after the article was published. Her name has been readded to the list with the approval of all of the authors.