Predesigned Hexanuclear CuIIand CuII/NiIIMetallacycles Featuring Six-Node Metallacoronand Structural Motifs

Three individually addressable spin qubits in a single molecule

An asymmetric bis-phenol-β-diketone (H₄L) has been designed as a ligand programmed to promote the assembly of a molecular arrangement composed of three magnetically exchanged [NiCu] pairs, each exhibiting an S = 1/2 spin. The latter are shown by EPR and magnetometry to be good qubit realizations and non-equivalent within the molecule in the solid state, as required for conditional quantum gates.

Modular [FeIII8MII6] n+ (MII = Pd, Co, Ni, Cu) Coordination Cages

The reaction of the simple metalloligand [Fe^IIIL₃] [HL = 1-(4-pyridyl)butane-1,3-dione] with a variety of different M^II salts results in the formation of a family of heterometallic cages of formulae [Fe^III₈Pd^II₆L₂₄]Cl₁₂ (1), [Fe^III₈Cu^II₆L₂₄(H₂O)₄Br₄]Br₈ (2), [Fe^III₈Cu^II₆L₂₄(H₂O)₁₀](NO₃)₁₂ (3), [Fe^III₈Ni^II₆L₂₄(SCN)₁₁Cl] (4), and [Fe^III₈Co^II₆L₂₄(SCN)₁₀(H₂O)₂]Cl₂ (5). The metallic skeleton of each cage describes a cube in which the Fe^III ions occupy the eight vertices and the M^II ions lie at the center of the six faces. Direct-current magnetic susceptibility and magnetization measurements on 3-5 reveal the presence of weak antiferromagnetic exchange between the metal ions in all three cases. Computational techniques known in theoretical nuclear physics as statistical spectroscopy, which exploit the moments of the Hamiltonian to calculate relevant thermodynamic properties, determine J_Fe-Cu = 0.10 cm^-1 for 3 and J_Fe-Ni = 0.025 cm^-1 for 4. Q-band electron paramagnetic resonance spectra of 1 reveal a significantly wider spectral width in comparison to [FeL₃], indicating that the magnitude of the Fe^III zero-field splitting is larger in the heterometallic cage than in the monomer.

A mixed valent heterometallic CuII/NaI coordination polymer with sodium–phenyl bonds

A mixed valent heterometallic Cu^II/Na^I coordination polymer (1) is generated by the reaction of a Schiff base ligand, (6,6′-(1E,1′E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-methoxyphenol)) with copper(ii) acetate and sodium perchlorate.

Self-assembled Co(II) molecular squares incorporating the bridging ligand 4,7-phenanthrolino-5,6:5',6'-pyrazine

Three high-spin tetranuclear cobalt(II) complexes have been prepared with the bridging ligand 4,7-phenanthrolino-5,6:5',6'-pyrazine (ppz) through metal-ion directed self-assembly. The complexes differ by the incorporation of three different coordinating anions: chloride, thiocyanide and selenocyanide. The physical properties of these complexes have been investigated in detail.

New nickel(II) and iron(II) helicates and tetrahedra derived from expanded quaterpyridines

As an extension of prior studies involving the linear quaterpyridine ligand, 5,5'''-dimethyl-2,2':5',5'':2'',2'''-quaterpyridine 1, the synthesis of the related expanded quaterpyridine derivatives 2 and 3 incorporating dimethoxy-substituted 1,4-phenylene and tetramethoxy-substituted 4,4'-biphenylene bridges between pairs of 2,2'-bipyridyl groups has been carried out via double-Suzuki coupling reactions between 5-bromo-5'-methyl-2'-bipyridine and the appropriate di-pinacol-diboronic esters using microwave heating. Reaction of 2 and 3 with selected Fe(II) or Ni(II) salts yields a mixture of both [M(2)L(3)](4+) triple helicates and [M(4)L(6)](8+) tetrahedra, in particular cases the ratio of the products formed was shown to be dependent on the reaction conditions; the respective products are all sufficiently inert to allow their chromatographic separation and isolation. Longer reaction times and higher concentrations were found to favour tetrahedron formation. The X-ray structures of solvated [Ni(2)(2)(3)](PF(6))(4), [(PF(6)) ⊂ Fe(4)(2)(6)](PF(6))(7), [Fe(4)(3)(6)](PF(6))(8) and [Ni(4)(3)(6)](PF(6))(8) have been determined, while the structure of the parent Fe(II) cage in the series, [(PF(6)) ⊂ Fe(4)(1)(6)](PF(6))(7), was reported previously. The internal volumes of the Fe(II) tetrahedral cages have been calculated and increase from 102 Å(3) for [Fe(4)(1)(6)](8+) to 227 Å(3) for [Fe(4)(2)(6)](8+) to 417 Å(3) for [Fe(4)(3)(6)](8+) and to an impressive 839 Å(3) for [Ni(4)(3)(6)](8+). The corresponding void volume in the triple helicate [Ni(2)(2)(3)](4+) is 29 Å(3).