The first paramagnetic borohydrido-bridged dinuclear nickel(II) complex, [(L)Ni^II ₂(μ_1,3-BH₄)]⁺, stabilised by a sterically demanding hexaaza-dithiophenolate macrocycle, has been obtained by the reaction of [(L)Ni^II ₂(μ-ClO₄)]⁺ with NⁿBu₄BH₄.

The synthesis and photophysical properties of four new hybrid salicylaldiminato-calix[4]arene ligands and their corresponding zinc(II) complexes are described. The Schiff bases were obtained from condensation reactions between cone-25,27-di(aminoethoxy)-26,28-dihydroxy-calix[4]arene and salicylaldehyde (H₂L¹) or o-vanillin (H₂L²) and 1,3-alt-25,27-di(aminoethoxy)-26,28-di(n-propyloxy)-calix[4]arene and 3,5-di-tert-butyl-salicylaldehyde (H₂L³) or o-vanillin (H₂L⁴). Complexation reactions were investigated by ESI-MS, IR, NMR, UV-vis absorption and steady-state and time resolved fluorescence spectroscopy, and X-ray crystallography. All ligands support 1 : 1 complexes (ZnL¹–ZnL⁴), with equilibrium constants derived from absorption spectrophotometry in the range log K₁₁ = 5.5–8.2 (MeCN or MeOH/CH₂Cl₂, I = 0.01 M). The zinc complexes show blue fluorescence, both in solution as well as in the solid state, with λ_em, Φ_f, and τ ranging from 472–504 nm, 0.11–0.60, and 2–9 ns, respectively. The nature of the substituents on the salicylaldiminato fragments was found to be the main parameter that influences the photophysical properties of the zinc complexes. Insights into the electronic nature of the UV-vis transitions were obtained with time dependent density functional theory (TD-DFT) calculations.

The ligating properties of the 24-membered macrocyclic dinucleating hexaazadithiophenolate ligand (L^Me)²⁻ towards the transition metal ions Cr^II, Mn^II, Fe^II, Co^II, Ni^II and Zn^II have been examined. It is demonstrated that this ligand forms an isostructural series of bioctahedral [(L^Me)M^II ₂(OAc)]⁺ complexes with Mn^II (2), Fe^II (3), Co^II (4), Ni^II (5) and Zn^II (6). The reaction of (L^Me)²⁻ with two equivalents of CrCl₂ and NaOAc followed by air-oxidation produced the complex [(L^Me)Cr^IIIH₂(OAc)]²⁺ (1), which is the first example for a mononuclear complex of (L^Me)²⁻. Complexes 2–6 contain a central N₃M^II(μ-SR)₂(μ-OAc)M^IIN₃ core with an exogenous acetate bridge. The Cr^III ion in 1 is bonded to three N and two S atoms of (L^Me)²⁻ and an O atom of a monodentate acetate coligand. In 2–6 there is a consistent decrease in the deviations of the bond angles from the ideal octahedral values such that the coordination polyhedra in the dinickel complex 5 are more regular than in the dimanganese compound 2. The temperature dependent magnetic susceptibility measurements reveal the magnetic exchange interactions in the [(L^Me)M^II ₂(OAc)]⁺ cations to be relatively weak. Intramolecular antiferromagnetic exchange interactions are present in the Mn^II ₂, Fe^II ₂ and Co^II ₂ complexes where J = −5.1, −10.6 and ∼−2.0 cm⁻¹ (H = −2JS₁S₂). In contrast, in the dinickel complex 5 a ferromagnetic exchange interaction is present with J = +6.4 cm⁻¹. An explanation for this difference is qualitatively discussed in terms of the bonding differences.