Electrochemical oxidation of diphenylamines with electron‐donating and electron‐withdrawing substituents in various combinations was investigated. It was shown that the subsequent reaction channels for the radical cations are dependent on the location and electronic properties of the substituents in both phenyl rings. Guidelines for the prediction of the dominant reaction path were formulated. The conclusions developed will be useful for planning electrosynthesis. Digital simulation of the voltammograms allowed estimating the mechanism of N,N‐diaryl‐5,10‐dihydrophenazine formation (which is one of the main reaction channels); the corresponding radical cations were isolated for the first time and characterized by X‐ray, electrochemical and spectral methods. Oxidation peak potentials for diarylaminyl anions (obtained using electrochemically generated base) were measured providing information for mechanistic estimation of anti/prooxidant activity of diarylamines in radical processes.

Ni(II) complexes containing (S)-o-[N-(N-benzylprolyl)amino]benzophenone as an auxiliary chiral moiety in the form of a Schiff base with α-amino acids (α-amino acid = glycine, alanine, dehydroalanine; Gly-Ni, Ala-Ni, and Δ-Ala-Ni) were subjected to various types of electrochemical activation (oxidation, reduction, and a treatment with electrogenerated base), affording regio- and diastereoselective synthesis of novel types of binuclear Ni(II) complexes via C–C coupling. New compounds were fully characterized by HRMS, MALDI-TOF, CD, and 1H and 13C NMR (including two-dimensional techniques) spectroscopy; two complexes were characterized by X-ray diffraction analysis. The structures of the novel complexes obtained via electrosynthesis completely match the predictions (made from preliminary voltammetric investigations of the starting complexes as well as from DFT estimations of the energy and symmetry of their frontier molecular orbitals) about the nature of chemical transformations which may follow the electron transfer steps. Electrochemical oxidation of Gly-Ni and Ala-Ni allows access to new dimeric complexes linked via benzophenone moieties in the Ni(II) coordination environment. These new binuclear Ni(II) complexes are of interest as chiral redox mediators for both oxidative and reductive transformations, since they exhibit quasi-reversible electrochemical behavior (their reduced and oxidized forms are stable, at least on the time scale of cyclic voltammetry). Three other binuclear Ni(II) complexes which were obtained via reductive dimerization of the Δ-Ala-Ni complex, via nucleophilic addition of electrochemically deprotonated Gly-Ni to Δ-Ala-Ni, and via oxidative electrochemical dimerization of deprotonated Gly-Ni are of interest as convenient precursors for the stereoselective preparation of diamino dicarboxylic acids HO(O)CCH(NH2)(CH2) n (NH2)CHC(O)OH (n = 2–0), since the obtained binuclear Ni(II)–Schiff base complexes can be easily disassembled using aqueous HCl in methanol.

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The crystal structures of the monoclinic and triclinic polymorphs of zoledronic acid, C5H10N2O7P2, have been established from laboratory powder X-ray diffraction data. The molecules in both polymorphs are described as zwitterions, namely 1-(2-hydroxy-2-phosphonato-2-phosphonoethyl)-1H-imidazol-3-ium. Strong intermolecular hydrogen bonds (with donor-acceptor distances of 2.60 Å or less) link the molecules into layers, parallel to the (100) plane in the monoclinic polymorph and to the (1-10) plane in the triclinic polymorph. The phosphonic acid groups form the inner side of each layer, while the imidazolium groups lie to the outside of the layer, protruding in opposite directions. In both polymorphs, layers related by translation along [100] interact through weak hydrogen bonds (with donor-acceptor distances greater than 2.70 Å), forming three-dimensional layered structures. In the monoclinic polymorph, there are hydrogen-bonded centrosymmetric dimers linked by four strong O-H...O hydrogen bonds, which are not present in the triclinic polymorph.