Oxime ligands are able to form stable binuclear species with copper(II) ions in aqueous solution. They also have a strong tendency to decrease the Mn+/(n-1)+ redox potentials of the central ions. Ligands possessing the hydroxyimino groups together with other powerful sigma-donor groups can be very efficient chelating agents able to facilitate the stabilisation of high oxidation states of 3d-metals. Here we report the synthesis, structural characterization and redox behaviour of mononuclear and binuclear complexes based on hydroxyiminoamide tetradentate open-chain ligands. In all mononuclear anionic complexes the central atom is situated in a square-planar surrounding of four nitrogen atoms. This pseudo-macrocyclic conformation is due to the presence of short intramolecular hydrogen bonds uniting the cis-oximate oxygen atoms. The square-planar surrounding of the strong sigma-donors facilitates efficient stabilization of the trivalent state of copper and nickel ions. In cyclic voltammetry studies the quasi-reversible processes M2+-->M3+ can be observed. In the binuclear complexes the coordinatively saturated octahedral ion M[prime or minute] is bound to the two oxygen atoms of the bridging oximate groups and the four nitrogen atoms of the tetradentate ligand tren. Two metal ions (M and M') are linked by the double cis-oximate bridge and are incorporated in a six-membered bimetallic chelate ring. Metallamacrocycle formation leads to certain changes in the structural parameters of the binuclear complexes as compared to those observed in the mononuclear species. Also the study of the electrochemical activity of binuclear complexes has shown important differences in their redox behaviour as compared to their mononuclear precursors.

A missing member of the tetraphenylmethane-based family of supramolecular tectons, tetrakis(4-phosphonophenyl)methane, TPPM (1), has been obtained, characterized, and reacted with organic amines that possess modulated conformational flexibility. The obtained adducts serve as a diverse platform for the investigation of the amine templating effect on phenyl embraces, the resulting supramolecular network, and its topology. Hirshfeld surface (HS) analysis has been employed for the investigation of phenyl embraces, which led to the indication of characteristic HS features of 4PE and 6PE phenyl embraces. One can also observe a new subtype of phenyl embrace, namely, HBA-PE (hydrogen bondassisted phenyl embrace), which constitutes the cooperation of two interactions: strong hydrogen bonding and a phenyl embrace. A topological insight into TPPM hydrogen-bonded networks is also provided. As a result, we found a connection of the amine template type with the periodicity of the underlying supramolecular network. Additionally, we report three previously unknown topologies. The obtainment of an unusual example of a phosphonic acid cocrystal with base (adduct 3) allowed for the determination of specific 2D fingerprint plot patterns for acid−base structures, with and without proton transfer.

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The first example of a Cu(II) [12]-MC-4 hydroxamic metallacrown compound containing a carboxyl group as a supporting donor function is described. The solution equilibria of malonomonohydroxamic acid (MACZ, H 2 L) with Cu(II) are investigated in aqueous solution using a combination of potentiometry, UV-vis absorption spectrophotometry, EPR spectroscopy and ESI mass spectrometry. Among the four complexes fitting the best speciation model ([CuL], [Cu 5 L 4 H À4 ] 2À , [CuL 2 ] 2À and [CuL 2 H À1 ] 3À ), a pentameric metallacrown molecule of composition Cu : L = 5 : 4 predominates in solution over the pH 4 to 11 range, and the corresponding complex was isolated in the solid state. The crystallization of the complex [Cu 5 L 4 H À4 ] 2À in the presence of [Cu(en) 2 (H 2 O) 2 ] 2+ cations resulted in the isolation of [Cu(en) 2 (H 2 O) 2 ] n [Cu(en) 2 (H 2 O)(m-H 2 O){Cu 5 (L 4 H À4 )(H 2 O) 3 } 2 ] n Á 20nH 2 O (1), whose crystal structure has been determined by X-ray analysis. The structure of 1 consists of centrosymmetric complex cations [Cu(en) 2 (H 2 O) 2 ] 2+ , infinite complex anionic chains [Cu(en) 2 (H 2 O)-(m-H 2 O){Cu 5 (L 4 H À4 )(H 2 O) 3 } 2 ] n 2nÀ and solvate water molecules. Within the complex anionic chains, the decanuclear double-decked bis([12]-MC-4) complex anions {Cu 5 (L 4 H À4 )(H 2 O) 3 } 2 4À are united by the [Cu(en) 2 (H 2 O) 2 ] 2+ complex cations due to the bridging function of the axial water molecule O (5). The magnetic behaviour of 1, studied in the temperature range 1.8-300 K, suggests the presence of both antiferromagnetic and ferromagnetic contributions to the observed magnetic susceptibility, resulting in a ground state of S = 2 per formula unit.