Sergio Sanz

Calix[4]arene-supported Fe(2)(III)Ln(2)(III) clusters

A series of Fe(III)(2)Ln(III)(2) clusters have been synthesised under facile bench top conditions. The resulting clusters pack in a manner akin to the calixarene solvate, and represent an important entry point to this new type of 3d-4f system.

p-tert-Butylcalix(8)arene: An extremely versatile platform for cluster formation**

p-tert-Butylcalix[4]arene is a bowl-shaped molecule capable of forming a range of polynuclear metal clusters under different experimental conditions. p-tert-Butylcalix[8]arene (TBC[8]) is a significantly more flexible analogue that has previously been shown to form mono- and binuclear lanthanide (Ln) metal complexes. The latter (cluster) motif is commonly observed and involves the calixarene adopting a near double-cone conformation, features of which suggested that it may be exploited as a type of assembly node in the formation of larger polynuclear lanthanide clusters. Variation in the experimental conditions employed for this system provides access to Ln(1), Ln(2), Ln(4), Ln(5), Ln(6), Ln(7) and Ln(8) complexes, with all polymetallic clusters containing the common binuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln(8)) are in fact based on metal octahedra or the building blocks of octahedra, with the identity and size of the final product dependent upon the basicity of the solution and the deprotonation level of the TBC[8] ligand. This demonstrates both the versatility of the ligand towards incorporation of additional metal centres, and the associated implications for tailoring the magnetic properties of the resulting assemblies in which lanthanide centres may be interchanged.

Progressive decoration of pentanuclear Cu(II) 12-metallacrown-4 nodes towards targeted 1- and 2D extended networks

The synthesis, structures and magnetic characterisation of a family of discrete planar pentanuclear Cu(II) 12-MC-4 metallacrowns of formulae [Cu5(L1)4(MeOH)4](ClO4)2 (1), [Cu5(L1)4(py)2](ClO4)2·py (2), [Cu5(L1)4(py)6](ClO4)2 (3) and [Cu5(L2)4(MeOH)4](ClO4)2·H2O (7) (where L1H2 = 2-(dimethylamino)phenylhydroxamic acid and L2H2 = 2-(amino)phenylhydroxamic acid) are reported. UV-vis and Electrospray MS studies indicate solution stability with respect to their {Cu5(L)4}2+ cores. Magnetic susceptibility measurements confirm strong antiferromagnetic exchange between the Cu(II) ions resulting in isolated S = 1/2 ground spin states. The introduction of ditopic co-ligands such as 4,4′-bipyridine (4,4′-bipy), pyrazine (pz) and 4,4′-azopyridine (4,4′-azp) results in their coordination at a number of axial Cu(II) sites within the {Cu5} metallacrown nodes to afford the extended networks {[Cu5(L1)4(4,4′-bipy)3](ClO4)2·(H2O)}n (4), {[Cu5(L1)4(4,4′-azp)2(MeOH)2](ClO4)2}n (5) and {[Cu5(L2)4(pz)2(MeOH)3](ClO4)2·MeOH}n (6).

Combining Complementary Ligands into one Framework for the Construction of a Ferromagnetically Coupled {[}Mn-12(III)] Wheel

Phenolic oxime and diethanolamine moieties have been combined into one organic framework, resulting in the formation of a novel ligand type that can be employed to construct a rare and unusual dodecametallic Mn wheel, within which nearest neighbours are coupled ferromagnetically.

[CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)

[CrIII8MII6]12+ (MII=Cu, Co) coordination cubes were constructed from a simple [CrIIIL3] metalloligand and a “naked” MII salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior.

A truncated [MnIII12] tetrahedron from oxime-based [MnIII3O] building blocks

The use of the novel pro-ligand H4L combining the complimentary phenolic oxime and diethanolamine moieties in one organic framework, results in the formation of the first example of a [Mn(III)12] truncated tetrahedron and an extremely rare example of a Mn cage conforming to an Archimedean solid.

p-tert-Butylcalix[8]arene: A support for sodium and sodium-manganese clusters that exhibit interesting self-assembly properties

A series of new sodium and mixed sodium/manganese clusters have been formed using p-tert-butylcalix[8]arene as a support. In all cases the calixarene adopts the pleated-loop conformation, and the resulting complexes show interesting self-assembly properties depending on the ligated solvent molecules around individual cluster cores.

Proton Cascade in a Molecular Solid: H/D Exchange on Mobile and Immobile Water†

Funding was provided by the Ministerio de Ciencia e Innovacion (Spain) under Grants MAT2011-27233-C02-01 and MAT2011-27233-C02-02 with cofinancing from the European Union Regional Development Fund (FEDER), and under the program CONSOLIDER-INGENIO in Molecular Nanoscience (reference CSD 2007- 00010). E.F.-V. thanks the Ministry of Education (Spain) for a predoctoral scholarship under the program “Becas y Contratos FPU” (reference AP2009-4211). Funding was also provided by the Diputacion General de Aragon (Spain). We acknowledge the services of the Servicio General de Apoyo a la Investigacion—SAI, University of Zaragoza.

Copper Keplerates: High-Symmetry Magnetic Molecules

Keplerates are molecules that contain metal polyhedra that describe both Platonic and Archimedean solids; new copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low-temperature physics does not necessarily reflect this symmetry.

Bis-Calix[4]arenes: From Ligand Design to the Directed Assembly of a Metal–Organic Trigonal Antiprism

Calix[4]arenes (C[4]s) are versatile platforms for the construction of polymetallic clusters containing paramagnetic metal ions. Synthetic modification at the C[4] methylene bridge allows for the design of bis-C[4]s that, depending on the linker employed, can be used to either dictate which clusters can be formed or direct the assembly of a new metal-organic polyhedron (MOP). The assembly resulting from the latter approach displays thermal stability and uptake of N2 or H2 gas, confirming that this is a viable route to the synthesis of new, functional supramolecular architectures.