Selective Gold Recovery and Catalysis in a Highly Flexible Methionine-Decorated Metal–Organic Framework

A novel chiral 3D bioMOF exhibiting functional channels with thio-alkyl chains derived from the natural amino acid l-methionine (<b>1</b>) has been rationally prepared. The well-known strong affinity of gold for sulfur derivatives, together with the extremely high flexibility of the thioether “arms” decorating the channels, account for a selective capture of gold­(III) and gold­(I) salts in the presence of other metal cations typically found in electronic wastes. The X-ray single-crystal structures of the different gold adsorbates <b>Au</b>^<b>III</b><b>@1</b> and <b>Au</b>^<b>I</b><b>@1</b> suggest that the selective metal capture occurs in a metal ion recognition process somehow mimicking what happens in biological systems and protein receptors. Both <b>Au</b>^<b>III</b><b>@1</b> and <b>Au</b>^<b>I</b><b>@1</b> display high activity as heterogeneous catalyst for the hydroalkoxylation of alkynes, further expanding the application of these novel hybrid materials

Slow Magnetic Relaxation in a Hydrogen-Bonded 2D Array of Mononuclear Dysprosium(III) Oxamates

The reaction of <i>N</i>-(2,6-dimethylphenyl)­oxamic acid with dysprosium­(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium­(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology

Slow Magnetic Relaxation in a Hydrogen-Bonded 2D Array of Mononuclear Dysprosium(III) Oxamates

The reaction of <i>N</i>-(2,6-dimethylphenyl)­oxamic acid with dysprosium­(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium­(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology

A Chiral, Photoluminescent, and Spin-Canted {Cu^IRe^IV₂}_<i>n</i> Branched Chain

A new heteroleptic 1D Cu^I–Re^IV coordination polymer of the formula {Cu^IRe^IVCl₄(μ-Cl)­(μ-pyz)­[Re^IVCl₄(μ-bpym)]}_<i>n</i>·<i>n</i>MeNO₂ (<b>1</b>; pyz = pyrazine, bpym = 2,2′-bipyrimidine) has been prepared through the Cu^I-mediated self-assembly of two different Re^IV metalloligands, namely, [ReCl₅(pyz)]⁻ and [ReCl₄(bpym)]. <b>1</b> consists of chiral branched chains with an overall rack-type architecture displaying photoemission and magnetic ordering. These results constitute a first step toward making new multifunctional magnetic materials based on mixed 3d–5d molecular systems

Dicopper(II) Metallacyclophanes with Oligo(<i>p</i>‑phenylene-ethynylene) Spacers: Experimental Foundations and Theoretical Predictions on Potential Molecular Magnetic Wires

Two novel double-stranded dicopper­(II) metallacyclophanes of formula (<i>n</i>Bu₄N)₄­[Cu₂(dpeba)₂]·­4MeOH·2Et₂O (<b>1</b>) and (<i>n</i>Bu₄N)₄[Cu₂(tpeba)₂]·12H₂O (<b>2</b>) have been prepared by the Cu^II-mediated self-assembly of the rigid (‘rod-like’) bridging ligands <i>N</i>,<i>N</i>′-4,4′-diphenylethynebis­(oxamate) (dpeba) and <i>N</i>,<i>N</i>′-1,4-di­(4-phenylethynyl)­phenylenebis­(oxamate) (tpeba), respectively. Single crystal X-ray diffraction analysis of <b>1</b> confirms the presence of a dicopper­(II)­tetraaza[3.3]­4,4′-diphenylethynophane metallacyclic structure featuring a very long intermetallic distance between the two square planar Cu^II ions [<i>r</i> = 14.95(1) Å]. The overall parallel-displaced π-stacked conformation of the two nearly planar para substituted diphenylethyne spacers [dihedral angle (ψ) of 7.8(1)°] leads to important deviations from the perpendicular orientation of the copper mean basal planes with respect to the facing benzene planes [dihedral angles (ϕ) of 56.4(1) and 58.4(1)°]. X-band EPR spectra together with variable-temperature magnetic susceptibility and variable-field magnetization measurements of <b>1</b> and <b>2</b>, both in solution and in the solid state, show the occurrence of a non-negligible, moderate to weak intramolecular antiferromagnetic coupling [−<i>J</i> = 3.9–4.1 (<b>1</b>) and 0.5–0.9 cm^–1 (<b>2</b>); <b>H</b> = −<i>J</i> <b>S</b>_<b>1</b>·<b>S</b>_<b>2</b> with <i>S</i>₁ = <i>S</i>₂ = <i>S</i>_Cu = 1/2]. Density functional calculations on the BS singlet (<i>S</i> = 0) and triplet (<i>S</i> = 1) spin states of the model complexes <b>1</b> and <b>2</b> with an ideal orthogonal molecular geometry (ψ = 0° and ϕ = 90°) support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the <i>d</i>_<i>xy</i> orbital of each square planar Cu^II ion through the predominantly π-type orbital pathway of the double <i>p</i>-diphenylethyne (<b>1</b>) and di­(phenylethynyl)­phenylene spacers (<b>2</b>). Time-dependent density functional calculations reproduce the observed bathochromic shift of the main intraligand (IL) π–π* transition in the electronic absorption spectra of <b>1</b> and <b>2</b> [λ₁ = 308 (<b>1</b>) and 316 nm (<b>2</b>)]. In the series of orthogonal model complexes <b>1</b>–<b>5</b> with linear oligo­(<i>p</i>-phenylene-ethynylene) (OPE) spacers, −C₆H₄(CCC₆H₄)_<i>n</i>– (<i>n</i> = 1–5), a linear increase of the IL π–π* transition energy with the reciprocal of the intermetallic distance is theoretically predicted [ν_max = 1.99 × 10⁴ + 2.15 × 10⁵ (1/<i>r</i>) (<i>S</i> = 0) or ν = 2.01 × 10⁴ + 2.18 × 10⁵ (1/<i>r</i>) (<i>S</i> = 1)], which clearly indicates that the effective π-conjugation length increases with the number of phenylethyne repeating units. This is accompanied by an exponential decay of the antiferromagnetic coupling with the intermetallic distance [−<i>J</i> = 1.08 × 10³ exp­(−0.31<i>r</i>)], which supports the ability of the extended π-conjugated OPEs to mediate the exchange interaction between the unpaired electrons of the two Cu^II centers with intermetallic distances in the range of 1.5–4.3 nm. Further developments may be then envisaged for this new family of oxamato-based dicopper­(II) oligo-<i>p</i>-phenylethynophanes on the basis of the unique ligand capacity to act as a molecular antiferromagnetic wire