Interaction of Co(II), Ni(II) and Cu(II) with dibenzo-substituted macrocyclic ligands incorporating both symmetrically and unsymmetrically arranged N, O and S donors

The synthesis and characterisation of four 17-membered, dibenzo-substituted macrocyclic ligands incorporating unsymmetrical arrangements of their N3S2, N3O2 and N3OS (two ligands) donor atoms are described; these rings complete the matrix of related macrocyclic systems incorporating both symmetric and unsymmetric donor sets reported previously. The X-ray structures of three of the new macrocycles are reported. In two of the Cu(II) structures only three of the possible five donor atoms present in the corresponding macrocyclic ligand bind to the Cu(II) site, whereas all five donors are coordinated in each of the remaining complexes. The interaction of Co(II), Ni(II) and Cu(II) with the unsymmetric macrocycle series has been investigated by potentiometric (pH) titration in 95% methanol; X-ray structures of two nickel and three copper complexes of these ligands, each exhibiting 1 : 1 (M :L) ratios, have been obtained. The results are discussed in the context of previous results for these metals with the analogous 17-membered ring systems incorporating symmetrical arrangements of their donor atoms, with emphasis being given to both the influence of the donor atom set, as well as the donor atom sequence, on the nature of the resulting complexes

Spin-State Patterning in an Iron(II) Tripodal Spin-Crossover Complex

A mononuclear iron(II) complex that displays a gradual two-step spin-crossover (SCO) transition is reported. The intermediate plateau (IP) occurs between HS0.40LS0.60 and HS0.30LS0.70 (HS = high spin; LS = low spin) ratios over the region of ca. 190-170 K. A phase change occurs at the IP, breaking the symmetry, resulting in six independent SCO sites compared to one at the 100% HS and LS plateau regions, respectively. Variableerature X-ray photoelectron spectroscopy shows that the SCO behavior is completely reversible among the HS, IP, and LS regions. The results both confirm and extend the related results for the above system described by Halcrow et al. (Kulmaczewski, R.; Cespedes, O.; Halcrow, M. A. Gradual Thermal Spin-Crossover Mediated By a Reentrant Z′ = 1 Z′ = 6 Z′ = 1 Phase Transition, Inorg. Chem. 2017, 56, 3144-3148) in a recent report

Metallo-supramolecular assemblies incorporating 1,3-and 1,4-aryl linked bis-beta-diketones - Some recent studies

A review of recent work in the authors' laboratories involving the interaction of 1,3- and 1,4-aryl linked bis-β-diketone derivatives with divalent and trivalent metal ions is presented. In some instances, bifunctional bridging ligands have been employed to extend the resulting structures from two to three dimensions. Examples of metallo-supramolecular dinuclear 'platforms', tetranuclear cofacial dimers, dinuclear helicates, trinuclear triangles, stepped metallo-polymers, a prismatic columnar polymer and large cavity-containing, tetranuclear tetrahedra are all discussed