Stephanie M. Taylor

Selective Metal Cation Capture by Soft Anionic Metal-Organic Frameworks via Drastic Single-Crystal-to-Single-Crystal Transformations

Flexible anionic metal-organic frameworks (MOFs) are transformed into neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs displays highly selective uptake of divalent transition-metal cations (e.g., Co(2+) and Ni(2+)) over alkali-metal cations (Li(+) and Na(+)).

A Family of Calix{[}4]arene-Supported {[}(Mn2Mn2II)-Mn-III] Clusters

In the cone conformation calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition-metal centres. Reaction of these molecules with manganese salts in the presence of an appropriate base (and in some cases co-ligand) results in the formation of a family of calixarene-supported [Mn(III)(2)Mn(II)(2)] clusters that behave as single-molecule magnets (SMMs). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs.

Calixarene-supported clusters: employment of complementary cluster ligands for the construction of a ferromagnetic [Mn5] cage

A combination of complementary cluster ligands results in the formation of a new calixarene-supported ferromagnetic [Mn(5)] cage that displays the characteristic bonding modes of each support.

Calix[4]arene supported clusters: a dimer of [MnIIIMnII] dimers

Phosphinate ligands allow for the transformation of a calix[4]arene supported [Mn(III)(2)Mn(II)(2)] tetramer cluster motif into an unusual [Mn(III)Mn(II)](2) dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates.

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.

Oxacalix[3]arene-supported supertetrahedron.

The initial use of oxacalix[3]arene in manganese chemistry affords an unusual [Mn(10)] supertetrahedron with an even more unusual oxidation state distribution.

Investigating the solid state hosting abilities of homo- and hetero-valent [Co7] metallocalix[6]arenes

A family of homo-valent [Co(II)(7)(OH)(6)(L(1))(6)](NO(3))(2) (1), [(MeOH)(2) is a subset of Co(II)(7)(OH)(6)(L(1))(6)](NO(3))(2) (2) (where L(1)H = 2-iminomethyl-6-methoxyphenol) and hetero-valent [(NO(3))(2) is a subset of Co(III)Co(II)(6)(OH)(6)(L(2))(6)](NO(3))·3MeCN (4) (where L(2)H = 2-iminophenyl-6-methoxyphenol) complexes possess metallic skeletons describing planar hexagonal discs. Their organic exteriors form double-bowl shaped topologies, and coupled with their 3-D connectivity, this results in the formation of molecular cavities in the solid state. These confined spaces are shown to behave as host units in the solid state for guests including solvent molecules and charge balancing counter anions. Magnetic susceptibility measurements on 2 and 4 reveal weak ferro- and ferrimagnetism, respectively. The utilisation of other Co(II) salt precursors gives rise to entirely different species including the mononuclear and trinuclear complexes [Co(II)(L(2))(2)] (5) and [Co(III)(2)Na(I)(1)(L(3))(6)](BF(4)) (6) (where L(3)H = 2-iminomethyl-4-bromo-6-methoxyphenol).

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).

Calixarene-supported rare-earth clusters: heteroatom bridge influences cluster composition

Rare-earth octahedra have been previously synthesised using p-tert-butylcalix[4]arene as a cluster support. Introduction of a heteroatom bridge in the calixarene framework, with concomitant alteration to the nature of the metal binding pocket, influences lanthanide composition in the cluster.

Homo- and heterometallic planes, chains and cubanes

The synthesis, structural and magnetic characterisation of a family of homo- and heterometallic complexes constructed with the Schiff base ligands 2-iminomethyl-6-methoxy-phenol (L1H) and 2-imino-6-methoxy-phenol (L2H), are discussed. Members include the heterometallic tetranuclear complexes of general formula [Na2M2(X)2(L1)4(Y)2] (where M = Fe(III), X = (-)OMe, Y = NO3(-) (1) and M = Ni(II), X = N3(-) and Y = MeCN (2)), each possessing a butterfly-like topology. We also report the formation of the heterometallic molecular cage [Na3Ni2(L1)6](ClO4) (3) whose metallic skeleton describes a [rare] trigonal bipyramid, the homometallic 1-D coordination polymer [Mn(L1)2(Cl)]n (4), and the tetranuclear cubane clusters [Mn(III)3Mn(IV)(O)3(OEt)(OAc)3(L1)3] (5) and [Ni4(μ3-OMe)4(L2)4(MeOH)4] (6). Dc and ac magnetic susceptibility studies on complexes 5 and 6 reveal S = 9/2 and S = 4 spin ground states.