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Reaction of Co(OAc) 2 ·4H 2 O and Hsal in a basic MeCN solution affords the hexadecanuclear wheel [Co 16 (sal) 16 (OAc) 16 ]·16MeCN (1·16MeCN) that displays ferromagnetic nearest neighbour exchange and has pseudo-calixarene character. Symmetry equivalent wheels self-assemble to form remarkable tubular networks of capsules in the extended structure.

A series of calix[4]arene-supported Ln(III)(6) clusters have been synthesised under facile bench top conditions. The magnetic and structural properties of these clusters are reported, the latter suggesting that the Ln(III)-calix[4]arene moiety may be used for the construction of other assemblies in a manner akin to that for the Mn(III)-calix[4]arene analogue., (This journal is © The Royal Society of Chemistry 2012)

We report the synthesis and magnetic characterisation of a series of planar [M₇] (M= Ni(II), Zn(II)) disc complexes [Ni₇(OH)₆(L₁)₆](NO₃)₂ (1), [Ni₇(OH)₆(L₁)₆](NO₃)₂·2MeOH (2), [Ni₇(OH)₆(L₁)₆](NO₃)₂·3MeNO₂ (3), [Ni₇(OH)₆(L₂)₆](NO₃)₂·2MeCN (4), [Zn₇(OH)₆(L₁)₆](NO₃)₂·2MeOH·H₂O (5) and [Zn₇(OH)₆(L₁)₆](NO₃)₂·3MeNO₂ (6) (where HL₁ = 2-iminomethyl-6-methoxy-phenol, HL₂ = 2-iminomethyl-4-bromo-6-methoxy-phenol). Each member exhibits a double-bowl pseudo metallocalix[6]arene topology whereby the individual [M₇] units form molecular host cavities which are able to accommodate various guest molecules (MeCN, MeNO₂ and MeOH). Magnetic susceptibility measurements carried out on complexes 1 and 4 indicate weak exchange between the Ni(II) centres.

Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent ‘expansion’ of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species.

The reaction between MnCl2·4H2O, 2,2′-bis-p-tBu-calix[4]arene (H8L1) and 2-(hydroxymethyl)pyridine (hmpH) in a basic dmf/MeOH solution results in the formation of the complex [Mn III10 Mn II4 (L1)3(hmp)4(μ3-O)4(μ3-OH)2(MeOH)4(dmf)6](dmf)4 (6) upon vapour diffusion of petroleum ether into the mother liquor. The crystals are in the monoclinic space group C2/c, with the asymmetric unit (ASU) comprising one half of the molecule. The structure describes a large S-shaped cluster (∼40 Å top to tail) where the unusual syn and anti conformations of the calixarene ligands results in two binding pockets each containing a [Mn III5 Mn II2 ] moiety comprised of two perpendicular, vertex-sharing [Mn4] butterflies. One butterfly possesses a [Mn III4 O4] core and the second a [Mn III2 Mn II2 O3] unit with the MnII ions in the central body positions. Magnetic susceptibility and magnetisation measurements reveal weak exchange interactions between the metal centres. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent ‘expansion’ of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are versatile ligands that, whilst also serving other purposes, can act as platforms for the synthesis of a wide range of 3 d, 4 f, and 3 d-4 f polymetallic clusters. The empirical metal ion binding rules established for calix[4]arene are closely mirrored by bis-calix[4]arene, a relatively new ligand in which two equivalents of the former are directly tethered at a methylene bridge position. The direct tethering within bis-calix[4]arene gives rise to some structural features that are related to calix[4]arene coordination chemistry, but the prevailing clusters have fascinating new topologies and coordination behaviors. Here, we present the synthesis of a family of new bis-calix[4]arene-supported 3 d-4 f clusters, as well as their structural characterization and magnetic properties. Comparison is drawn with calix[4]arene coordination chemistry, showing logical extension of common structural fragments and cluster capping behaviors upon moving to bis-calix[4]arene. This approach therefore holds great potential for tuning cluster formation and composition at a high level through subsequent ligand alteration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are versatile ligands capable of forming a wide range of cluster motifs when reacted with 3d, 4for 3d/4fmetal ions. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to explore cluster formation with these alternative building blocks. Here, we present the synthesis of a range of bis-calix[4]arenes that are tethered by alkyl chains, as well as exploratory structural studies into cluster-forming reactions. Single crystals were formed in four cases, and from the X-ray structures elucidated it is possible to conclude that sufficiently long alkyl tethers allow for the formation of established cluster topologies without disruption to the core coordination chemistry. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to synthesise alternative supramolecular building blocks. This paper describes the synthesis of a range of alkyl-tethered bis-calix[4]arenes, as well as exploratory structural studies into polymetallic cluster formation. [ABSTRACT FROM AUTHOR]

The central MnII ions in a series of calix[4]arenestabilised butterflies can be sequentially replaced with LnIII ions, maintaining the structural integrity of the molecule but transforming its magnetic properties. The replacement of MnII for GdIII allows for the examination of the transferability of spin-Hamiltonian parameters within the family as well as permitting their reliable determination. The introduction of the 4f ions results in weaker intramolecular magnetic exchange, an increase in the number of low-lying excited states, and an increase in magnetisation relaxation, highlighting the importance of exchange over single-ion anisotropy for the observation of SMM behaviour in this family of complexes. The presence of the [TMII/III(TBC[4])(OH)(solvent)] metalloligand (TM=transition metal, TBC=p-tBu-calix[4]arene) suggests that magnetic calix[n]arene building blocks can be employed to encapsulate a range of different "guests" within structurally robust "hosts". [ABSTRACT FROM AUTHOR]

Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3 d-4 f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures. [ABSTRACT FROM AUTHOR]

A new calix[4]arene-supported MnIIIMnII cluster, formed by the introduction of 3,5-dichlorobenzoate to a system known to afford Mn2IIIMn2II Single-Molecule Magnets (SMMs), assembles in a layered manner through halogen interactions; structural and magnetic properties of this new cluster are presented. [ABSTRACT FROM AUTHOR]

A bis-phenolate that has structural similarities to both calix[4]arene and the oxacalix[ n]arenes provides access to a 'butterfly'-like Mn4 cluster in which all metals are in the oxidation state+3. Specific properties of this ligand, in comparison to others in the literature, offer a route to influencing the orientation of the Jahn-Teller axes within this cluster motif, which possesses a rare oxidation state arrangement. [ABSTRACT FROM AUTHOR]

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 Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 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 (Ln8) 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. [ABSTRACT FROM AUTHOR]

We report the synthesis and magnetic characterisation of a series of planar [M7] (M = NiII, ZnII) disc complexes [Ni7(OH)6(L1)6](NO3)2(1), [Ni7(OH)6(L1)6](NO3)2·2MeOH (2), [Ni7(OH)6(L1)6](NO3)2·3MeNO2(3), [Ni7(OH)6(L2)6](NO3)2·2MeCN (4), [Zn7(OH)6(L1)6](NO3)2·2MeOH·H2O (5) and [Zn7(OH)6(L1)6](NO3)2·3MeNO2(6) (where HL1= 2-iminomethyl-6-methoxy-phenol, HL2= 2-iminomethyl-4-bromo-6-methoxy-phenol). Each member exhibits a double-bowl pseudometallocalix[6]arene topology whereby the individual [M7] units form molecular host cavities which are able to accommodate various guest molecules (MeCN, MeNO2and MeOH). Magnetic susceptibility measurements carried out on complexes 1and 4indicate weak exchange between the NiIIcentres. [ABSTRACT FROM AUTHOR]

The ligand bis(5-tert-butyl-2-hydroxy-3-hydroxymethyl-phenyl)methane, a flexible calix[n]arene analogue, is employed to construct an unusual linear [Ln3] trimer. [ABSTRACT FROM AUTHOR]

A series of FeIII2LnIII2clusters 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. [ABSTRACT FROM AUTHOR]

Phosphinate ligands allow for the transformation of a calix[4]arene supported [MnIII2MnII2] tetramer cluster motif into an unusual [MnIIIMnII]2dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates. [ABSTRACT FROM AUTHOR]

New pseudo-trigonal planar supramolecular building blocks housing tri-capped trigonal prismatic [Cu9] clusters have been isolated from the facile reaction of Cu(ii) salts with p-tBut-calix[4]arene. [ABSTRACT FROM AUTHOR]

Supramolecular Chemistry In the Full Paper on page 2804 ff., S. Piligkos, E. K. Brechin, S. J. Dalgarno et al. report the use of methylene ‐ bridged calix[4]arenes as versatile ligand supports for the construction of polymetallic clusters with fascinating magnetic properties. Empirical metal ‐ ion binding rules established for this building block help to partially rationalise the complex assembly process. Linking calix[4]arenes at the methylene bridge provides improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis ‐ calix[4]arenes and transition metal ions or 3d ‐ 4f combinations display characteristic features of the analogous calix[4]arene ‐ supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent ‘expansion’ of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species. [ABSTRACT FROM AUTHOR]

Abstract: Methylene-bridged calix[4]arenes have emerged as excellent ligands for polynuclear cluster formation. In this contribution methylene- and oxa-bridged calix[6]arenes have been examined as candidates for cluster formation with cobalt(II) nitrate, affording two markedly different structures. The nature of the structures is highly dependent on the bridging atoms. Reaction of p-tert-butylcalix[6]arene with cobalt(II) nitrate in DMF results in the formation of a coordination polymer in which the calixarene adopts a ‘double-partial’ cone conformation. A similar reaction with p-tert-butyltetrahomodioxacalix[6]arene affords a discrete complex in which a central heteroatom also coordinates to the metal centre, with the calixarene in a ‘double-cone’ conformation. The synthesis and structure of both compounds is presented. [Copyright &y& Elsevier]

Abstract: Methylene-bridged calix[4]arenes have emerged as excellent ligands for polynuclear cluster formation. In this contribution methylene- and oxa-bridged calix[6]arenes have been examined as candidates for cluster formation with cobalt(II) nitrate, affording two markedly different structures. The nature of the structures is highly dependent on the bridging atoms. Reaction of p-tert-butylcalix[6]arene with cobalt(II) nitrate in DMF results in the formation of a coordination polymer in which the calixarene adopts a ‘double-partial’ cone conformation. A similar reaction with p-tert-butyltetrahomodioxacalix[6]arene affords a discrete complex in which a central heteroatom also coordinates to the metal centre, with the calixarene in a ‘double-cone’ conformation. The synthesis and structure of both compounds is presented. [Copyright &y& Elsevier]