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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]

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]

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]