The study reports an advance in designing copper-based redox sensing MRI contrast agents. Although the data demonstrate that copper(II) complexes are not able to compete with lanthanoids species in terms of contrast, the redox-dependent switch between diamagnetic copper(I) and paramagnetic copper(II) yields a novel redox-sensitive contrast moiety with potential for reversibility.

The supramolecular structure of the title molecule, [Ca(C7H4ClO4S)(H2O)6](C7H4ClO4S)·H2O, contains alternating organic and inorganic layers along the b direction. The sulfonate group on one of the aryl units is coordinated to Ca, while the other does not form any interaction with a Ca atom.

The X-ray crystal structures of (N,N'-bis-(o-amidobenzilidene)-1,3-diaminopropane)nickel (Niambpr), (N,N'-bis-(o-amidobenzilidene)-1,4-diaminobutane)nickel (Niambut), (N,N'-bis-(o-thiobenzilidene)-1,4-diaminobutane)nickel(II) (Nitsalbut), {bis-acetonitrile-(N,N'-bis-(o-aminobenzyl)-1,2-diaminoethane)}nickel(II) tetrafluoroborate [Ni(H₄amben)(MeCN)₂] [BF₄]₂, {bis-O-acetato-(N,N'-bis-(o-aminobenzyl)-1,2-diaminoethane)}nickel(II) [Ni(H₄amben)(OAc)₂ · H₂O] and {bis-O-acetato-(N,N'-bis-(o-aminobenzyl)-1,3-diaminopropane)}nickel(II) [Ni(H₄ambpr)(OAc)₂] are presented. These structures complete the structural characterisation of the simple unsubstituted Schiff's base complexes with N₄ and N₂S₂ donor sets and allow us to assess the effects of donor groups and polymethylene chain length on the coordination geometries of nickel(II). The hydrogenated N4 complexes offer an insight into the effects of increased flexibility and character of the internal nitrogen donors. Unlike the parent N4 imine species the hydrogenated amine species do not deprotonate at the peripheral nitrogen donors and do not seem to be restricted to the meridial plane of the nickel.

The title tetradentate Schiff base complex (systematic name: {2,2'-[propane-1,3-diylbis(nitrilomethylidyne)]benzenethiolato- κ⁴S,N,N',S'}nickel(II) 1,4-dioxane solvate), [Ni(C₁₇H₁₆-N₂S₂)]·C₄H₈O₂, contains an Ni atom coordinated within a tetrahedrally distorted planar N₂S₂ environment, with average Ni-N and N-S bond lengths of 1.922 (1) and 2.167 (1) Å, respectively.

We have isolated and crystallographically characterized the three homologous compounds N,N'-bis(2-methoxybenzylidene) ethane-1,2-diamine (MeSalen), C₁₈H₂₀N₂O₂, N,N'-bis-(2-methoxybenzylidene)propane-1,3-diamine (MeSalpr), C₁₉-H₂₂N₂O₂, and N,N'-bis(2-methoxybenzylidene)butane-1,4-diamine (MeSalbu), C₂₀H₂₄N₂O₂. In contrast with MeSalpr, the molecules of MeSalen and MeSalbu, which have an even number of methylene units, have crystallographic '1' symmetry. Comparing these methoxy-substituted species with their hydroxy equivalents shows that the aryl rings rotate upon removal of the O-H···N hydrogen bonds. The packing of MeSalen and MeSalpr is controlled by C-H···π interactions, whereas that of MeSalbu has only van der Waals contacts.