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Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with Cu(NO3)2·3H2O and N-methyldiethanolamine (Me-deaH2) in a basic dmf/MeOH mixture affords [CuII16(L)2(Me-dea)4(μ4-NO3)2(μ-OH)4(dmf)3.5(MeOH)0.5(H2O)2](H6L)·16dmf·4H2O (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu12], in which the four capping metal ions are the CuII ions housed in the calix[4]arene polyphenolic pockets. The [CuII8] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the N-methyldiethanolamine co-ligands forming dimeric [CuII2] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated H6L2- ligand per [Cu16] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an S = 1 ground state, while EPR is consistent with a large zero-field splitting.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with MnCl2·4H2O, GdCl3·6H2O and 2,6-pyridinedimethanol (H2pdm) affords [MnIIIMnIIGdIII(H3L)(pdmH)(pdm)(MeOH)2(dmf)]·3MeCN·dmf (3·3MeCN·dmf) upon vapour diffusion of MeCN into the basic dmf/MeOH mother liquor. 3 crystallises in the tetragonal space group P41212 with the asymmetric unit comprising the entire cluster. The highly unusual core contains a triangular arrangement of MnIIIMnIIGdIII ions housed within a [MnIIIMnIIGdIII(OR)4]4- partial cubane. Magnetic susceptibility and magnetisation data reveal best fit parameters JMn(II)-Mn(III) = +0.415 cm-1, JMn(III)-Gd(III) = +0.221 cm-1, JMn(II)-Gd(III) = -0.258 cm-1 and DMn(III) = -4.139 cm-1. Theoretically derived magnetic exchange interactions, anisotropy parameters, and magneto-structural correlations for 3 are in excellent agreement with the experimental data.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with MnCl2·4H2O, GdCl3·6H2O and 2,6-pyridinedimethanol (H2pdm) affords [MnIIIMnIIGdIII(H3L)(pdmH)(pdm)(MeOH)2(dmf)]·3MeCN·dmf (3·3MeCN·dmf) upon vapour diffusion of MeCN into the basic dmf/MeOH mother liquor. 3 crystallises in the tetragonal space group P41212 with the asymmetric unit comprising the entire cluster. The highly unusual core contains a triangular arrangement of MnIIIMnIIGdIII ions housed within a [MnIIIMnIIGdIII(OR)4]4- partial cubane. Magnetic susceptibility and magnetisation data reveal best fit parameters JMn(II)-Mn(III) = +0.415 cm-1, JMn(III)-Gd(III) = +0.221 cm-1, JMn(II)-Gd(III) = -0.258 cm-1 and DMn(III) = -4.139 cm-1. Theoretically derived magnetic exchange interactions, anisotropy parameters, and magneto-structural correlations for 3 are in excellent agreement with the experimental data.

The reaction of MnCl2·4H2O with HL ((1-methyl-1H-imidazol-2-yl)methanol) and pdH2 (1, 3 propanediol) in a basic MeCN solution results in the formation of a mixed-valence [Mn20] cationic cluster and two [MnIICl4] counter anions. The metallic skeleton of the cluster describes two geometrically equivalent mixed-valent, linked [MnIII6MnII4] supertetrahedra in which nearest-neighbor metal ions have a different oxidation state. Magnetic susceptibility, magnetization data and heat capacity measurements support evidence of predominant ferromagnetic correlations, leading to a s = 22 spin ground state for the [MnIII6MnII4] supertetrahedra, which are pair-linked by a weak antiferromagnetic coupling. The properties are discussed in the context of the magnetocaloric effect and the potential application of this compound in cryogenic refrigeration. [ABSTRACT FROM AUTHOR]

The solvothermal reaction of FeCl2 ⋅ 4H2O and H4TBC[4] in a basic dmf/EtOH solution affords an [FeIII18] Keplerate conforming to a stellated cuboctahedron. Magnetic and heat capacity measurements reveal spin frustration effects arising from the high symmetry. A crossover between inverse and direct magnetocaloric effects is observed at ~10 K for applied‐field changes lower than 3 T. [ABSTRACT FROM AUTHOR]

The solvothermal reaction of FeCl2 ⋅ 4H2O and H4TBC[4] in a basic dmf/EtOH solution affords an [FeIII18] Keplerate conforming to a stellated cuboctahedron. Magnetic and heat capacity measurements reveal spin frustration effects arising from the high symmetry. A crossover between inverse and direct magnetocaloric effects is observed at ~10 K for applied‐field changes lower than 3 T. [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.

C-alkylpyrogallol[4]arenes (PgCs) have been studied for their ability to form metal-organic nanocapsules (MONCs) through coordination to appropriate metal ions. Here we present the synthesis and characterization of an MnII/MnIII-seamed MONC in addition to its electrochemical and magnetic behavior. This MONC assembles from 24 manganese ions and 6 PgCs, while an additional metal ion is located on the capsule interior, anchored through the introduction of bridging nitrite ions. The latter originate from an in situ redox reaction that occurs during the self-assembly process, thus representing a new route to otherwise unobtainable nanocapsules.

Calix[4]arenes are versatile ligands, capable of supporting the formation of a wide variety of polymetallic clusters comprising 3d, 4f or 3d-4f metal ions. Calixarene-based metal ion fragments act as both bridging and structure capping moieties in these systems, and this behaviour is systematically extended upon moving to bis-calix[4]arene, a relatively new ligand in which two calix[4]arenes are tethered at the methylene bridge position. N,O-Ligands greatly influence cluster formation with bis-calix[4]arene, affording a remarkable mixed-valence [MnMnMn] cluster that displays coordination chemistry typical of each ligand type, but also new structure capping behaviour for the latter.

Calix[4]arenes are versatile ligands, capable of supporting the formation of a wide variety of polymetallic clusters comprising 3d, 4f or 3d-4f metal ions. Calixarene-based metal ion fragments act as both bridging and structure capping moieties in these systems, and this behaviour is systematically extended upon moving to bis-calix[4]arene, a relatively new ligand in which two calix[4]arenes are tethered at the methylene bridge position. N,O-Ligands greatly influence cluster formation with bis-calix[4]arene, affording a remarkable mixed-valence [MnMnMn] cluster that displays coordination chemistry typical of each ligand type, but also new structure capping behaviour for the latter.

Reaction of [VO(OR)3] (R = Et, nPr) with 2,2′-diphenylglycine afforded the alkoxide-bridged dimers {[VO(OR)(μ-OR)][Ph2C(NH2)(CO2)]}2, whereas use of benzilic acid, in the presence of alkali metals, afforded 16-membered metallocycles {V8(O)4M(OR)8[Ph2C(OH)(CO2)]12} (M = <1 Na, K). For the ring systems, magnetic susceptibility data is consistent with mixed-valence vanadium with an average oxidation state of 3.5. The dimer and ring systems are capable of the ring opening polymerisation (ROP) of ε-caprolactone under N2, air, or as melts affording mostly low to medium molecular weight cyclic and linear products. [ABSTRACT FROM AUTHOR]

Calix[n]arenes offer ideal chemical functionality through the polyphenolic lower rim to construct nano-sized coordination clusters with lanthanide (Ln) metal ions (e.g., Nd III10 , Gd III8). However, the number of metal centers they can accommodate is still limited compared to that achievable with smaller ligands (e.g., Gd III140 , Gd III104). Here, we exploit a combination of the "anion template strategy" and "templating ligands" to synthesise three highly symmetric (D3h, trigonal planar) Ln III18 (Ln = La, Nd, and Gd) systems, representing the largest calix[n]arene-based coordination clusters yet. The Ln III18 fragment is templated by a chloride anion located at the center of the cluster, wherefrom twelve μ3-OH− ligands bind 'internally' to the eighteen LnIII ions. 'Externally' the metallic skeleton is connected by p-tert-butylcalix[8]arene, oxo, chloro and carbonate ligands. The crystal packing in the lattice reveals large cylindrical channels of ∼26 Å in diameter, whose pore volume corresponds to ∼50% of the unit cell volume (using a 1.2 Å spherical probe radius). Magnetic measurements reveal the predominance of weak antiferromagnetic exchange in the Gd analog. Heat capacity data of Gd III18 reveal a high magnetic entropy with −ΔSm = 23.7 J K−1 kg−1, indicating potential for engineering magnetic refrigerant materials with calix[8]arenes. [ABSTRACT FROM AUTHOR]

Reaction of 2,2′-bis-p-tBu-calix[4]arene (H8L) with Cu(NO3)2·3H2O and N-methyldiethanolamine (Me-deaH2) in a basic dmf/MeOH mixture affords [Cu II16 (L)2(Me-dea)4(μ4-NO3)2(μ-OH)4(dmf)3.5(MeOH)0.5(H2O)2](H6L)·16dmf·4H2O (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu12], in which the four capping metal ions are the CuII ions housed in the calix[4]arene polyphenolic pockets. The [Cu II8 ] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the N-methyldiethanolamine co-ligands forming dimeric [Cu II2 ] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated H6L2− ligand per [Cu16] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an S = 1 ground state, while EPR is consistent with a large zero-field splitting. [ABSTRACT FROM AUTHOR]