7 research outputs found
Directed <i>Ortho</i>-Lithiation of Aminophosphazenes: An Efficient Route to the Stereoselective Synthesis of <i>P</i>āChiral Compounds
<i>Ortho</i>-directed lithiation of <i>P</i>,<i>P</i>-diphenylaminophosphazenes followed by electrophilic quench is described as an efficient process for synthesizing <i>P</i>-chiral <i>ortho</i>-functionalized derivatives in high yields and diastereoselectivities. The method allows the tunable preparation of structurally diverse enantiopure <i>P</i>-chiral compounds including phosphinic and phosphinothioic amides, phosphinic esters, phosphine oxides, and <i>o</i>-aminophosphines
Series of Metal Organic Frameworks Assembled from Ln(III), Na(I), and Chiral Flexible-Achiral Rigid Dicarboxylates Exhibiting Tunable UVāvisāIR Light Emission
Two series of isoreticular chiral metalāorganic
frameworks
assembled from LnĀ(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), NaĀ(I),
and chiral flexible-achiral rigid dicarboxylate ligands, formulated
as [NaLnĀ(Tart)Ā(BDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S1</b>)
and [NaLnĀ(Tart)Ā(biBDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S2</b>) (H<sub>2</sub>Tart = tartaric acid; H<sub>2</sub>BDC = terephthalic
acid; H<sub>2</sub>biBDC = biphenyl-4,4ā²-dicarboxylic acid),
were obtained as single phases under hydrothermal conditions. The
compounds have been studied by single-crystal and powder X-ray diffraction,
thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR),
scanning electron microscopy (SEM-EDX), elemental analysis, and X-ray
thermodiffractometry. The catalytic activity has been also investigated.
The photoluminescence properties of selected compounds have been investigated,
exhibiting room temperature tunable UVāvisāIR light
emission
Series of Metal Organic Frameworks Assembled from Ln(III), Na(I), and Chiral Flexible-Achiral Rigid Dicarboxylates Exhibiting Tunable UVāvisāIR Light Emission
Two series of isoreticular chiral metalāorganic
frameworks
assembled from LnĀ(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), NaĀ(I),
and chiral flexible-achiral rigid dicarboxylate ligands, formulated
as [NaLnĀ(Tart)Ā(BDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S1</b>)
and [NaLnĀ(Tart)Ā(biBDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S2</b>) (H<sub>2</sub>Tart = tartaric acid; H<sub>2</sub>BDC = terephthalic
acid; H<sub>2</sub>biBDC = biphenyl-4,4ā²-dicarboxylic acid),
were obtained as single phases under hydrothermal conditions. The
compounds have been studied by single-crystal and powder X-ray diffraction,
thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR),
scanning electron microscopy (SEM-EDX), elemental analysis, and X-ray
thermodiffractometry. The catalytic activity has been also investigated.
The photoluminescence properties of selected compounds have been investigated,
exhibiting room temperature tunable UVāvisāIR light
emission
Antisymmetric Exchange in Triangular Tricopper(II) Complexes: Correlation among Structural, Magnetic, and Electron Paramagnetic Resonance Parameters
Two new trinuclear copperĀ(II) complexes, [Cu<sub>3</sub>(Ī¼<sub>3</sub>-OH)Ā(daat)Ā(Hdat)<sub>2</sub>(ClO<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>]Ā(ClO<sub>4</sub>)<sub>2</sub>Ā·2H<sub>2</sub>O (<b>1</b>) and [Cu<sub>3</sub>(Ī¼<sub>3</sub>-OH)Ā(aaat)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]Ā(ClO<sub>4</sub>)<sub>2</sub>Ā·3H<sub>2</sub>O (<b>2</b>) (daat = 3,5-diacetylamino-1,2,4-triazolate,
Hdat = 3,5-diamino-1,2,4-triazole, and aaat = 3-acetylamino-5-amino-1,2,4-triazolate),
have been prepared from 1,2,4-triazole derivatives and structurally
characterized by X-ray crystallography. The structures of <b>1</b> and <b>2</b> consist of cationic trinuclear copperĀ(II) complexes
with a Cu<sub>3</sub>OH core held by three <i>N</i>,<i>N</i>-triazole bridges between each pair of copperĀ(II) atoms.
The copper atoms are five-coordinate with distorted square-pyramidal
geometries. The magnetic properties of <b>1</b> and <b>2</b> and those of five other related 1,2,4-triazolato tricopperĀ(II) complexes
with the same triangular structure (<b>3ā7</b>) (whose
crystal structures were already reported) have been investigated in
the temperature range of 1.9ā300 K. The formulas of <b>3ā7</b> are [Cu<sub>3</sub>(Ī¼<sub>3</sub>-OH)Ā(aaat)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]Ā(NO<sub>3</sub>)<sub>2</sub>Ā·H<sub>2</sub>O (<b>3</b>), {[Cu<sub>3</sub>(Ī¼<sub>3</sub>-OH)Ā(aat)<sub>3</sub>(Ī¼<sub>3</sub>-SO<sub>4</sub>)]Ā·6H<sub>2</sub>O}<sub><i>n</i></sub> (<b>4</b>), and [Cu<sub>3</sub>(Ī¼<sub>3</sub>-OH)Ā(aat)<sub>3</sub>AĀ(H<sub>2</sub>O)<sub>2</sub>]ĀAĀ·<i>x</i>H<sub>2</sub>O [A = NO<sub>3</sub><sup>ā</sup> (<b>5</b>), CF<sub>3</sub>SO<sub>3</sub><sup>ā</sup> (<b>6</b>), or ClO<sub>4</sub><sup>ā</sup> (<b>7</b>); <i>x</i> = 0 or 2] (aat =3-acetylamino-1,2,4-triazolate). The magnetic
and electron paramagnetic resonance (EPR) data have been analyzed
by using the following isotropic and antisymmetric exchange Hamiltonian: <i>H</i> = ā<i>J</i>[<i>S</i><sub>1</sub><i>S</i><sub>2</sub> + <i>S</i><sub>2</sub><i>S</i><sub>3</sub>] ā <i>j</i>[<i>S</i><sub>1</sub><i>S</i><sub>3</sub>] + <i>G</i>[<i>S</i><sub>1</sub> Ć <i>S</i><sub>2</sub> + <i>S</i><sub>2</sub> Ć <i>S</i><sub>3</sub> + <i>S</i><sub>1</sub> Ć <i>S</i><sub>3</sub>]. <b>1</b>ā<b>7</b> exhibit strong antiferromagnetic coupling
(values for both ā<i>J</i> and ā<i>j</i> in the range of 210ā142 cm<sup>ā1</sup>) and antisymmetric
exchange (<i>G</i> varying from to 27 to 36 cm<sup>ā1</sup>). At low temperatures, their EPR spectra display high-field (<i>g</i> < 2.0) signals indicating that the triangles present
symmetry lower than equilateral and that the antisymmetric exchange
is operative. A magneto-structural study showing a lineal correlation
between the CuāOāCu angle of the Cu<sub>3</sub>OH core
and the isotropic exchange parameters (<i>J</i> and <i>j</i>) has been conducted. Moreover, a model based on Moriyaās
theory that allows the prediction of the occurrence of antisymmetric
exchange in the tricopperĀ(II) triangles, via analysis of the overlap
between the ground and excited states of the local CuĀ(II) ions, has
been proposed. In addition, analytical expressions for evaluating
both the isotropic and antisymmetric exchange parameters from the
experimental magnetic susceptibility data of triangular complexes
with local spins (<i>S</i>) of <sup>1</sup>/<sub>2</sub>, <sup>3</sup>/<sub>2</sub>, or <sup>5</sup>/<sub>2</sub> have been
purposely derived. Finally, the magnetic and EPR results of this work
are discussed and compared with those of other tricopperĀ(II) triangles
reported in the literature
Phyllanthus emblica
The experimentally observed stereomutation of spiro-1,2-oxaphosphetanes
is shown by DFT calculations to proceed through successive M<sub>B2</sub> or M<sub>B4</sub> and M<sub>B3</sub> mechanisms involving two, four,
and three Berry pseudorotations at phosphorus, respectively. Oxaphosphetane
decomposition takes place in a single step via a polar transition
state. The calculated activation parameters for this reaction are
in good agreement with those determined experimentally
A Binuclear Mn<sup>III</sup> Complex of a Scorpiand-Like Ligand Displaying a Single Unsupported Mn<sup>III</sup>āOāMn<sup>III</sup> Bridge
The crystal structure of a binuclear Mn<sup>III</sup> complex of
a scorpiand-like ligand (<b>L</b>) displays an unsupported single
oxo bridging ligand with a Mn<sup>III</sup>āOāMn<sup>III</sup> angle of 174.7Ā°. Magnetic susceptibility measurements
indicate strong antiferromagnetic coupling between the two metal centers.
DFT calculations have been carried out to understand the magnetic
behavior and to analyze the nature of the observed JahnāTeller
distortion. Paramagnetic <sup>1</sup>H NMR has been applied to rationalize
the formation and magnetic features of the complexes formed in solution
Cycloaurated Phosphinothioic Amide Complex as a Precursor of Gold(I) Nanoparticles: Efficient Catalysts for A<sup>3</sup> Synthesis of Propargylamines under Solvent-Free Conditions
A C,S-cycloaurated complex based
on an ortho-substituted phosphinothioic
amide framework has been synthesized in high yield through tinĀ(IV)āAuĀ(III)
transmetalation from the corresponding chlorodimethylstannyl derivative.
The latter was prepared in a two-step process involving directed ortho
lithiation/quenching with Me<sub>3</sub>SnCl followed by Me/Cl exchange.
The tinĀ(IV) and goldĀ(III) complexes have been characterized in solution
and in the solid state. In both complexes, the phosphinothioic amide
moiety acts as a CāCāPāS pincer ligand with formation
of five-membered-ring metalacycles. The use of the goldĀ(III) complex
in the amineāaldehydeāalkyne (A<sup>3</sup>) three-component
coupling synthesis of propargylamines showed that the compound is
transformed into the Sonogashira-type <i>o</i>-alkynylphosphinothioic
amide with generation of AuĀ(I) nanoparticles with an average size
of around 7 nm. These nanoparticles proved to be excellent catalysts
in A<sup>3</sup> coupling processes, providing propargylamines in
high yields under solvent-free conditions with loadings as low as
0.1 mol % and without the use of additives