Tandem templating strategies facilitate the assembly of calix[8]arene-supported Ln18 clusters.

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., NdIII10, GdIII8). However, the number of metal centers they can accommodate is still limited compared to that achievable with smaller ligands (e.g., GdIII140, GdIII104). Here, we exploit a combination of the "anion template strategy" and "templating ligands" to synthesise three highly symmetric (D3h, trigonal planar) LnIII18 (Ln = La, Nd, and Gd) systems, representing the largest calix[n]arene-based coordination clusters yet. The LnIII18 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 GdIII18 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.

Synthesis and characterization of two self-assembled [Cu6Gd3] and [Cu5Dy2] complexes exhibiting the magnetocaloric effect, slow relaxation of magnetization, and anticancer activity.

Two new paths for coordination driven self-assembly reactions under the binding support of 2-((1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H2L) have been discovered from the reactions of Cu(ClO4)2·6H2O, NEt3 and GdCl3/DyCl3·6H2O in MeOH/CHCl3 (2 : 1) medium. A similar synthetic protocol is useful to provide two different types of self-aggregated molecular clusters [Cu6Gd3(L)3(HL)3(µ3-Cl)3(µ3-OH)6(OH)2]ClO4·4H2O (1) and [Cu5Dy2(L)2(HL)2(µ-Cl)2(µ3-OH)4(ClO4)2(H2O)6](ClO4)2·2NHEt3Cl·21H2O (2). The adopted reaction procedure established the importance of the HO- and Cl- ions in the mineral-like growth of the complexes, derived from solvents and metal ion salts. In the case of complex 1, one GdIII center has been trapped at the central position of the core upheld by six µ3-OH and three µ3-Cl groups, whereas for complex 2 one CuII center was trapped using four µ3-hydroxo and two µ-chlorido groups. The magnetothermal behavior of 1 has been examined for a magnetocaloric effect of -ΔSm = 11.3 J kg-1 K-1 at 2 K for ΔH = 7 T, whereas the magnetic susceptibility measurements of 2 showed slow magnetic relaxation with Ueff = 15.8 K and τ0 = 9.8 × 10-7 s in zero external dc field. Cancer cell growth inhibition studies proved the potential of both the complexes with interestingly high activity for the Cu6Gd3 complex against human lung cancer cells. Both complexes 1 and 2 also exhibited DNA and human serum albumin (HSA) binding abilities in relation to the involved binding sites and thermodynamics.

Employment of a new tripodal ligand for the synthesis of cobalt(II/III), nickel(II), and copper(II) clusters: magnetic, optical, and thermal properties.

The employment of 2-(ß-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.