Employment of a New Tripodal Ligand for the Synthesis of Cobalt(II/III), Nickel(II), and Copper(II) Clusters: Magnetic, Optical, and Thermal Properties

Abstract

The employment of 2-(β-naphthalideneamino)-2-(hydroxymethyl)-1-propanol (LH(3)) in cobalt, nickel, and copper chemistry has led to the isolation of five new metallic complexes with interesting magnetic properties. More specifically, the reaction of Co(OAc)(2)·4H(2)O with LH(3) in MeOH in the presence of NEt(3) under solvothermal conditions forms the complex [Co(III)(2)Co(II)(3)(L)(2)(LH)(2)(L')(OAc)]·8.5MeOH (1·8.5MeOH; L' = monoanion of 2-hydroxy-1-naphthaldehyde), while in nickel chemistry, a similar reaction of Ni(OAc)(2)·6H(2)O with LH(3) in MeCN in the presence of NEt(3) under high pressure/temperature forms the complex [Ni(II)(LH(2))(2)]·2MeCN (2·2MeCN). Repeating the same reaction in MeOH and switching from Ni(OAc)(2)·4H(2)O to NiSO(4)·4H(2)O produces the complex [Ni(II)(4)(HL)(3)(OMe)(MeOH)(3)](SO(4))(0.5)·2MeOH (3·2MeOH) under solvothermal conditions. Furthermore, in copper chemistry, the reaction of Cu(2)(OAc)(4)·2H(2)O with LH(3) in the presence of NEt(3) in MeOH under solvothermal conditions affords the complex [Cu(II)(4)(LH)(4)] (4), while the same reaction under ambient temperature and pressure conditions forms [Cu(II)(4)(LH)(4)] ·3.5MeOH·2.25H(2)O (5·3.5MeOH·2.25H(2)O). Complex 1 is a mixed-valent [Co(III)(2)Co(II)(3)] complex, consisting of three edge-sharing [Co(3)] triangles. Complex 2 is a nickel(II) monomer in which the central metal is found in an octahedral geometry, while complex 3 describes a [Ni(II)(4)] cubane. Complexes 4 and 5 may be considered as structural isomers because they possess the same formulas but different topologies: 4 describes a highly distorted [Cu(II)(4)(OR)(4)](4+) eight-membered ring, while 5 consists of a distorted [Cu(II)(4)(μ(3)-OR)(4)](4+) cubane. In addition, 5 can be converted to 4 in excellent yield under solvothermal conditions. Direct-current magnetic susceptibility studies have been carried out in the 5-300 K range for complexes 1 and 3-5, revealing the possibility of a high-spin ground state for 1, an S = 4 ground state for 2, and diamagnetic ground states for 4 and 5.

Enneanuclear [Ni6Ln3] Cages: [LnIII3] Triangles Capping [NiII6] Trigonal Prisms Including a [Ni6Dy3] Single-Molecule Magnet

“…These new 4f-containing species, either 3d−4f or purely 4f, display extremely large energy barriers for the reorientation of the magnetization, assuming, of course, that an Arrhenius analysis is valid for such systems. 4 We recently reported the use of the naphthalene-based triol ligand H 3 L [L = 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol, Scheme 1] for the synthesis of polynuclear 3d complexes 5 and Mn-4f complexes. 6 Herein, we report the use X-ray Crystallography.…”

Cobalt(ii/iii), nickel(ii) and copper(ii) coordination clusters employing a monoanionic Schiff base ligand: synthetic, topological and computational mechanistic aspects

“…22 for Co1 and 3.24 for Co2). The ligand undergoes another oxidation (H 2 L 4 Scheme 1) and the methyl group connected to the pyrazolone ring is transformed to a carboxylate, as assigned by the 1.238(5)Å and 1.275(4)Å bond distances, for C31-O7 and C31-O6, respectively.…”

“…This owes to their wide range of useful properties such as strong biological activity, [2][3][4] ease of access and versatile coordination abilities. As a result, CCs using ligands of this nature are of special importance and many examples of their applications in material science, [5][6][7] catalysis, [8][9][10][11][12] biological processes, [13][14][15] molecular magnetic materials, [16][17][18][19][20][21][22][23] photochemistry, 24,25 and nanostructure studies, 26,27 have been explored. In particular, Schiff bases formed from o-vanillin as starting material have been of significant interest and their coordination abilities along with various metal centres have been investigated thoroughly leading to very interesting results.…”

A family of [MnIII6LnIII2] rod-like clusters

“…[4] Especially in the former case, the compounds that have been found to function as SMMs have grown exponentially; a phenomenon firstly observed for "traditional" transition metal centers like Mn, Fe, Co and Ni, [3] has now expanded to include 3d-4d/5d, 3d-4f, as well as 4f-and 5fcompounds; [5] most importantly, the properties of these "new" candidates seem to be very promising towards technological applications, and species with extremely large energy barriers for the re-orientation of the magnetization have been isolated, [6] given that an Arrhenius analysis is valid for such systems. [7] We recently reported the use of the naphthalene-based triol ligand LH 3 (= 2-(β-naphthalideneamino)-2-hydroxymethyl-1propanol, Scheme 1) in Co(II/III), Ni(II) and Cu(II) chemistry leading to the formation of a [Co III 2 Co II 3 ], [Ni 4 ] and two [Cu 4 ] clusters, [8] and we have now expanded our studies in mixedmetal Mn-Ln chemistry, and herein we report the use of this triol ligand for the synthesis of a family of octanuclear [Mn III 6 Ln III 2 ] complexes.…”