We report the synthesis and structural diversity of Zn(II) metal-organic framework (MOF) with in situ formation of tetrazole ligand 3-ptz [3-ptz = 5-(3-pyridyl)tetrazolate] as a function pH. By varying the initial reaction pH, we obtain high-quality crystals of the noncentrosymmetric three-dimensional MOF Zn(3-ptz)₂, mixed phases involving the zinc-aqua complex [Zn(H₂O)₄(3-ptz)₂]·4H₂O, and two-dimensional MOF crystals Zn(OH)(3-ptz) with a tunable microrod morphology, keeping reaction time, temperature, and metal–ligand molar ratio constant. Structures are characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV–vis spectroscopy. We discuss the observed structural diversity in terms of the relative abundance of hydroxo-zinc species in solution for different values of pH.

The addition of water to a chloroform solution of the Cu₆ trigonal prism complex [Cu₆(μ₆F)(μ₂OH)(μ₃OCH₃)₂(μ₂OCH₃)₂(3,5-Me₂pz)₆] (1) (3,5-Me₂pz⁻ = 3,5-dimethylpyrazolate) results in the formation of the Cu₆ planar hexagonal ring complex [Cu₆(μ₂OH)₆(3,5-Me₂pz)₆]·CH₃CN·CHCl₃ (2). A simple mechanism for this structural re-arrangement is proposed, in which 2 can be viewed as a hydrolysis product of 1. This process is clearly noticeable in the magnetic properties, which change from spin frustrated with a weak antiferromagnetic coupling in 1, to strongly antiferromagnetic in 2. Interestingly, the hexagonal ring complex 2 self-assembles in the solid state to form a porous hexagonal tubular structure containing guest solvent molecules that can be removed and CO₂-exchanged without loss of crystallinity.

In the present work, the synthesis and structural characterization of four new polyoxovanadoborate (BVO) frameworks based on the [V₁₂B₁₈O₆₀H₆]¹⁰⁻ polyanion are reported: (NH₄)₈(1,3-diapH₂)[V₁₂B₁₈O₆₀H₆]·5H₂O (1), K₈(NH₄)₂[V₁₂B₁₈O₆₀H₆]·18H₂O (2), K₁₀[V₁₂B₁₈O₆₀H₆]·10H₂O (3) and K₈Cs₂[V₁₂B₁₈O₆₀H₆]·10H₂O (4). A global antiferromagnetic behaviour is observed for these 10V^IV/2V^V mixed valence clusters. The magnetic data of 1, 2 and 3, which present different countercation environments, show that 1 is more coupled than 2 and 3. DFT calculations show that the positive charges strongly influence the polarization mechanism of the spin density of the vanadyl groups and the extent of the magnetic orbitals, therefore corroborating the experimental observation of the quenching effect of the magnetic coupling between vanadium centres of 2 and 3.

Magnetic analogues of Alq ₃ give rise to molecular/ferromagnetic interfaces with specific hybridization, opening the door to interesting spintronic effects.

A series of hybrid organo–inorganic mononuclear lanthanoid complexes, [n-NBu₄]₃[LnH(PW₁₁O₃₉)(phen)₂]·H₂O, denoted as LM⁴-1-Ln (Ln = Dy^III, Tb^III, Eu^III, Nd^III, Er^III, Ho^III and Gd^III), were synthesized via hydrothermal synthesis and were structurally characterized by X-ray diffraction. The optical properties of all complexes have been investigated in the solid state. The temperature-dependent emission spectra of LM⁴-1-Dy, LM⁴-1-Tb and LM⁴-1-Eu complexes show intense lanthanoid emissions in the visible region, while LM4-1-Nd shows near-infrared (NIR) luminescence. The Eu^III complex shows typical strong red emissions from the ⁵D₀ → ⁷F_0,1,2,3,4 transitions, with the CIE colour coordinates (0.631,0.364), the colour purity value of 83.9% and a quantum yield of up to 4.3%, suggesting that the organic fragment has an effect on the optical properties compared to fully inorganic systems, making this complex very attractive as a red component of light-emitting diodes. The luminescence decays of LM⁴-1-Dy, LM⁴-1-Tb and LM⁴-1-Eu exhibit a biexponential behaviour, with τ_AV = 4.1(7) μs, 0.35(2) ms and 0.94(3) ms, respectively. The values obtained for Judd–Ofelt intensity parameters Ω₂ and Ω₄ support the interaction between the Eu^III and the ligands. Furthermore, those with Er^III and Ho^III present weak emissions in the visible region. The T-dependent photoluminescence results show that the LM⁴-1-Dy, LM⁴-1-Tb and LM⁴-1-Nd complexes have good temperature sensitivity, demonstrating that the materials have the potential to be used as a sensing element for luminescent thermometers in different temperature ranges.

The first family of hybrid mononuclear organic–inorganic lanthanoid complexes is reported, based on [PW₁₁O₃₉]⁷⁻ and 1,10-phenanthroline ligands. This hybrid approach causes a dramatic improvement of the relaxation time (×1000) with a decrease of the optimal field while maintaining the U_eff of the inorganic analogues.