Formation of Tetranuclear Nickel(II) Complexes with Schiff-Bases: Crystal Structures and Magnetic Properties

The cubane-type structure is a typical representative of tetranuclear coordination compounds. In this work, two anionic Schiff-base ligands, (L1)2− and (L2)2−, each offering an O^N^O coordination pocket, ligate four NiII ions into a [Ni4O4] cubane core. The ligands are H2L1 = 2−[[(3-ethoxy-2−hydroxyphenyl) methylene]amino]benzenemethanol and H2L2 = 2−[[(5-fluoro-2−hydroxyphenyl)methylene]amino]benzenemethanol. In both compounds, [Ni4(L1)4(EtOH)4] (1) and [Ni4(L2)4(MeOH)4] (2), alkoxy oxygens of the ligands act in a bridging μ3-O binding mode. Magnetic susceptibility and magnetization data for compounds 1 and 2 are presented. The Ni–O–Ni bond angles of the cubane core determined from single crystal X-ray diffraction data play a key role for a magneto-structural correlation. Dominant intracube ferromagnetic behavior is observed, and the coupling parameters were determined for both compounds, leading to nonzero spin ground states in accordance with the broadly accepted bond angle guideline.

Phosphorescence at Low Temperature by External Heavy-Atom Effect in Zinc(II) Clusters

Luminescent Zn^II clusters [Zn₄ L₄ (μ₃ -OMe)₂ X₂ ] (X=SCN (1), Cl (2), Br (3)) and [Zn₇ L₆ (μ₃ -OMe)₂ (μ₃ -OH)₄ ]Y₂ (Y=I^- (4), ClO₄ ^- (5)), HL=methyl-3-methoxysalicylate, exhibiting blue fluorescence at room temperature (λ_max =416≈429 nm, Φ_em =0.09-0.36) have been synthesised and investigated in detail. In one case the external heavy-atom effect (EHE) arising the presence of iodide counter anions yielded phosphorescence with a long emission lifetime (λ_max =520 nm, τ=95.3 ms) at 77 K. Single-crystal X-ray structural analysis and time-dependent density-functional theory (TD-DFT) calculations revealed that their emission origin was attributed to the fluorescence from the singlet ligand-centred (¹ LC) excited state, and the phosphorescence observed in 4 was caused by the EHE of counter anions having strong CH-I interactions.

Weak ferromagnetism derived from spin canting in an amido-bridged homochiral Mn(iii) 1-D coordination polymer

An amido-bridged homochiral one-dimensional (1D) Mn(iii) coordination polymer behaves as a weak ferromagnet arising from spin canting with a coercive field of 3.0 kOe.

Creating capsules with cubanes

A sextuply linked capsule incorporating two Ni(ii) cubane units is formed when Ni(ii) salts are reacted with N-aminoalkyl salicylamidato ligands in a 4 : 3 ratio in methanol. With a short (propyl) alkyl substituent, additional chloride counter ions are included in the cavity by occupation of one apex of each of the linked cubanes, while with a longer (pentyl) substituent, perchlorate and tetrafluoroborate anions are included, probably by H-bonding involving hydroxyl groups on the inner apices of the cubanes, indicating that the cavity can be regarded as suited to binding of hydrophilic units despite the lipophilic character of its links. The dicubane capsules show ferromagnetic behaviour typical of Ni(ii) cubanes in general, with coupling constants dependent upon the nature of the salt-derived counter anions.

Wheel-type heterometallic ferromagnetic clusters: [Ni7−xMx(HL)6(μ3-OMe)4(μ3-OH)2]Cl2 (M = Zn, Co, Mn; x = 1, 3)

Wheel-type heptanuclear heterometallic clusters display metal ion dependent ferromagnetic properties and express single molecule magnet behavior based on the magnetic anisotropy.