Polynuclear metal clusters using polyalkoxide ligands

We have investigated the use of calix[4]arenes in 3d and 3d/4f chemistry which produced a family of 7 new complexes. These are: [MnIII2MnII2(OH)2(TBC4)2(DMF)6] (1) , the analogous version with C4 (2). [MnIII4GdIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (3), [MnIII4TbIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (4), [MnIII4DyIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (5), [CuII9(OH)3(TBC4)3Cl2(DMSO)6](CuICl2)·DMSO (6·DMSO) (6) and [CuII9(OH)3(TBC4)3(NO3)2(DMSO)6](NO3)· DMSO (7·DMSO) (7). We continued with a series of Pseudo Metallocalix[6]arene planar disc complexes : [Ni7(OH)6(L1)6](NO3)2 (8), [Ni7(OH)6(L1)6](NO3)2.2MeOH (9), [Ni7(OH)6(L1)6](NO3)2.3MeNO2 (10), [Ni7(OH)6(L2)6](NO3)2.2MeCN (11), [Zn7(OH)6(L1)6](NO3)2.2MeOH.H2O (12) and [Zn7(OH)6(L1)6](NO3)2.3MeNO2 (13) and in the final part of this thesis we present a family of tetranuclear mixed valent Mn complexes using the tripodal ligand heedH2 : [MnII2MnIV2O2(heed)2(EtOH)6Br2]Br2 (14), [MnII2MnIV2O2(heed)2(H2O)2Cl4] (15), [MnII2MnIV2O2(heed)2(heedH2)2](ClO4)4 (16), [MnII2MnIV2O2(heed)2(MeCN)2(H2O)2(bpy)2](ClO4)4 (17), [MnII2MnIV2O2(heed)2(bpy)2Br4] (18); and the 2-D network of tetranuclear MnII/IV clusters {[MnII2MnIV2O2(heed)2(H2O)2(MeOH)2(dca)2]Br2}n (19). In total nineteen new complexes are reported. Studies of the magnetic properties show that 1 and 2 are SMM’s, whilst complex 3 is an excellent magnetic refrigerant for low-temperature applications and 4 and 5 behave as low-temperature molecular magnets

[Mn(4)(III)Ln(4)(III)] Calix[4]arene Clusters as Enhanced Magnetic Coolers and Molecular Magnets

The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [MnIII4LnIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of LnIII ions housed within a square of MnIII ions. Magnetic studies reveal that 1 has a large number of molecular spin states that are populated even at the lowest investigated temperatures, while the ferromagnetic limit S = 22 is being approached only at the highest applied fields. This, combined with the high magnetic isotropy, makes the complex an excellent magnetic refrigerant for low-temperature applications. Replacement of the isotropic GdIII ions with the anisotropic TbIII and DyIII ions “switches” the magnetic properties of the cluster so that 2 and 3 behave as low-temperature molecular magnets, displaying slow relaxation of the magnetization.M.E. thanks the Spanish Ministry for Science and Innovation for grants MAT2009-13977-C03 and CSD2007- 00010.Peer Reviewe

A family of double-bowl <i>pseudo</i> metallocalix[6]arene discs

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 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 NiII centres

\u27Metal complexes as ligands\u27 for the synthesis of coordination polymers: A MnIII monomer as a building block for the preparation of an unprecedented 1-D {Mn\u3csup\u3eII\u3c/sup\u3eMn\u3csup\u3eIII\u3c/sup\u3e}n linear chain

A relatively unexplored synthetic route in redox-active Mn(II/III) coordination chemistry has been employed toward the preparation of a new mixed-valence MnII/III 1-D linear chain from the reaction of [MnIII(sacb)2]-precursor with a MnII source, where sacbH2 is the Schiff base ligand N-salicylidene-2-amino-5-chlorobenzoic acid. The mononuclear (Pr2NH2)[MnIII(sacb)2] (1) compound was obtained in excellent yields (\u3e85%) from the 1:2:3 reaction of Mn(O2CMe)2·4H2O, sacbH2 and Pr2NH, respectively. In 1, the two doubly deprotonated sacb2- ligands act as Ocarboxylate, Nimine, Ophenoxide-tridentate chelates, while the second carboxylate O atom of sacb2- is dangling and H-bonded to the Pr2NH2+ countercation. Complex 1 was subsequently used as a \u27ligand\u27 to react stoichiometrically with the \u27metal\u27 Mn(NO3)2· 4H2O thus leading to the 1-D coordination polymer ([MnIIMnIII(sacb)2(H2O)2(MeOH)2](NO3))n (2) in good yields (~50%). The removal of Pr2NH2+ from the vicinity of the [MnIII(sacb)2]-metalloligand has rendered possible (vide infra) the coordination of the second Ocarboxylate of sacb2- to neighboring (MnII(H2O)2(MeOH)2)2+ units, and consequently the formation of the 1-D polymer 2. Direct-current (dc) magnetic susceptibility studies revealed the presence of very weak antiferromagnetic exchange interactions between alternating MnIII and MnII atoms with a coupling constant of J =-0.08 cm-1 for g = 2.00. The combined results demonstrate the potential of the \u27metal complexes as ligands\u27 approach to yield new mixed-valence Mn(II/III.)coordination polymers with interesting structural motifs and physicochemical properties

Molecular and supramolecular Ni(II) wheels from alpha-benzoin oxime

The use of alpha-benzoin oxime in Ni(II) chemistry leads to the formation of a family of unusual molecular and supramolecular wheels

Planar [Ni7] discs as double-bowl, pseudometallacalix[6]arenehost cavities

We report three heptanuclear[Ni-7] complexes with planar disc-like cores, akin to double-bowl metallocalix[6]arenes, which form molecular H-bonded host cavities

Molecular and supramolecular Ni(II) wheels from alpha-benzoin oxime

The use of alpha-benzoin oxime in Ni(II) chemistry leads to the formation of a family of unusual molecular and supramolecular wheels.</p