16 research outputs found
Circularly Polarized Luminescence from an Eu(III) Complex Based on 2‑Thenoyltrifluoroacetyl-acetonate and a Tetradentate Chiral Ligand
A new
chiral complex {[Eu<b>L</b>(tta)<sub>2</sub>(H<sub>2</sub>O)]ÂCF<sub>3</sub>SO<sub>3</sub>; <b>L</b> = <i>N</i>,<i>N</i>′-bisÂ(2-pyridylmethylidene)-1,2-(<i>R</i>,<i>R</i> + <i>S</i>,<i>S</i>)-cyclohexanediamine;
tta = 2-thenoyltrifluoroacetyl-acetonate} has
been synthesized and characterized from a structural and spectroscopic
point of view. The molecular structure in the solid state shows the
presence of one chiral <b>L</b>, two tta, and one water molecules
bound to the metal center. <b>L</b> and tta molecules can efficiently
harvest and transfer to EuÂ(III) the UV light absorbed in the 250–400
nm range. The forced electric-dipole <sup>5</sup>D<sub>0</sub> → <sup>7</sup>F<sub>2</sub> emission band dominates the EuÂ(III) emission
spectra recorded in the solid state and in solution of acetonitrile
or methanol and the calculated intrinsic quantum yield of the metal
ion is around 40–50%. The light emitted by the enantiopure
complex shows a sizable degree of polarization with a maximum value
of the emission dissymmetry factor (<i>g</i><sub>lum</sub>) equal to 0.2 in methanol solution. If compared with the complex
in the solid state or in acetonitrile solution, then the first coordination
sphere of EuÂ(III) when the complex is dissolved in methanol is characterized
by the presence of one CH<sub>3</sub>OH molecule instead of water.
This fact is related to different EuÂ(III) CPL signatures in the two
solvents
Boron Functionalization and Unusual B–C Bond Activation in Rhodium(III) and Iridium(III) Complexes with Diphenylbis(pyrazolylborate) Ligands (Ph<sub>2</sub>Bp)
The
RhÂ(III) and IrÂ(III) pentamethylcyclopentadienyl compounds [MÂ(Cp*)Â(κ<sup>2</sup>-Ph<sub>2</sub>Bp)ÂCl] (M = Rh, <b>1</b>; M = Ir, <b>4</b>) were readily prepared from interaction of the salt KÂ[Ph<sub>2</sub>Bp] (Ph<sub>2</sub>Bp = diphenylbisÂ(pyrazolyl)Âborate) and
the [MÂ(Cp*)ÂCl<sub>2</sub>]<sub>2</sub> dimer precursors in dichloromethane
under anhydrous conditions. When the same reactions were carried out
in non-anhydrous conditions by using acetonitrile as solvent, we observed,
in the case of Rh, both B–N bond hydrolysis and Rh–CÂ(Ph)
bond activation with the formation of the hydroxyÂ(pyrazolyl)Âborate
complex [RhÂ(Cp*)Â(Ph)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBPh<sub>2</sub>}]
(<b>2</b>). In contrast, in the case of Ir only B–N hydrolysis
was observed and the ionic species [IrÂ(Cp*)Â(Hpz)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBPh<sub>2</sub>}]Cl (<b>5</b>) was obtained, upon
coordination of the liberated Hpz. Additionally, by reaction of <b>1</b> with AgClO<sub>4</sub> in acetonitrile, the ionic [RhÂ(Cp*)Â(Ph)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBÂ(OH)}]ÂClO<sub>4</sub> (<b>3</b>) was isolated.
Complexes <b>1</b>–<b>3</b> and <b>5</b> have
been structurally characterized by X-ray crystallography. Spectral
studies have been performed for all species, together with a computational
DFT modeling investigation. A decomposition mechanism for the diphenylbisÂ(pyrazolyl)Âborate
ligand in the different complexes is proposed
Boron Functionalization and Unusual B–C Bond Activation in Rhodium(III) and Iridium(III) Complexes with Diphenylbis(pyrazolylborate) Ligands (Ph<sub>2</sub>Bp)
The
RhÂ(III) and IrÂ(III) pentamethylcyclopentadienyl compounds [MÂ(Cp*)Â(κ<sup>2</sup>-Ph<sub>2</sub>Bp)ÂCl] (M = Rh, <b>1</b>; M = Ir, <b>4</b>) were readily prepared from interaction of the salt KÂ[Ph<sub>2</sub>Bp] (Ph<sub>2</sub>Bp = diphenylbisÂ(pyrazolyl)Âborate) and
the [MÂ(Cp*)ÂCl<sub>2</sub>]<sub>2</sub> dimer precursors in dichloromethane
under anhydrous conditions. When the same reactions were carried out
in non-anhydrous conditions by using acetonitrile as solvent, we observed,
in the case of Rh, both B–N bond hydrolysis and Rh–CÂ(Ph)
bond activation with the formation of the hydroxyÂ(pyrazolyl)Âborate
complex [RhÂ(Cp*)Â(Ph)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBPh<sub>2</sub>}]
(<b>2</b>). In contrast, in the case of Ir only B–N hydrolysis
was observed and the ionic species [IrÂ(Cp*)Â(Hpz)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBPh<sub>2</sub>}]Cl (<b>5</b>) was obtained, upon
coordination of the liberated Hpz. Additionally, by reaction of <b>1</b> with AgClO<sub>4</sub> in acetonitrile, the ionic [RhÂ(Cp*)Â(Ph)Â{κ<sup>2</sup>-(pz)Â(OH)ÂBÂ(OH)}]ÂClO<sub>4</sub> (<b>3</b>) was isolated.
Complexes <b>1</b>–<b>3</b> and <b>5</b> have
been structurally characterized by X-ray crystallography. Spectral
studies have been performed for all species, together with a computational
DFT modeling investigation. A decomposition mechanism for the diphenylbisÂ(pyrazolyl)Âborate
ligand in the different complexes is proposed
Synthesis and Structural Characterizations of New Coordination Polymers Generated by the Interaction Between the Trinuclear Triangular SBU [Cu<sub>3</sub>(μ<sub>3</sub>‑OH)(μ-pz)<sub>3</sub>]<sup>2+</sup> and 4,4′-Bipyridine. 3°
The reactions of 4,4′-bipyridine
with selected trinuclear
triangular copperÂ(II) complexes, [Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub>(RCOO)<sub>2</sub>L<sub><i>x</i></sub>], [pz = pyrazolate anion, R = CH<sub>3</sub>(CH<sub>2</sub>)<sub><i>n</i></sub> (2 ≤ <i>n</i> ≤
5); L = H<sub>2</sub>O, MeOH, EtOH] yielded a series of 1D coordination
polymers (CPs) based on the repetition of [Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub>] secondary building units joined
by bipyridine. The CPs were characterized by conventional analytical
methods (elemental analyses, ESI-MS, IR spectra) and single crystal
XRD determinations. An unprecedented 1D CP, generated through the
bipyridine bridging hexanuclear copper clusters moieties, two 1D CPs
presenting structural analogies, and two monodimensional tapes having
almost exactly superimposable structures, were obtained. In one case,
the crystal packing makes evident the presence of small, not-connected pores, accounting for ca.
6% of free cell volume
Interaction of the Trinuclear Triangular Secondary Building Unit [Cu<sub>3</sub>(μ<sub>3</sub>‑OH)(μ-pz)<sub>3</sub>]<sup>2+</sup> with 4,4′-Bipyridine. Structural Characterizations of New Coordination Polymers and Hexanuclear Cu<sup>II</sup> Clusters. 2°
By reacting 4,4′-bipyridine
(bpy) with selected trinuclear
triangular Cu<sup>II</sup> complexes, [Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub>Â(RCOO)<sub>2</sub>Â(LL′)] [pz = pyrazolate anion; R = CH<sub>3</sub>, CH<sub>3</sub>CH<sub>2</sub>, CH<sub>2</sub>î—»CH, CH<sub>2</sub>î—»CÂ(CH<sub>3</sub>); L, L′ = Hpz, H<sub>2</sub>O, MeOH] in MeOH, the
substitution of monotopic ligands by ditopic bpy was observed. Depending
on the stoichiometric reaction ratios, different compounds were isolated
and structurally characterized. One- and two-dimensional coordination
polymers (CPs), as well as two hexanuclear Cu<sup>II</sup> clusters
were identified. One of the hexanuclear clusters self-assembles into
a supramolecular three-dimensional structure, and its crystal packing
shows the presence of two intersecting channels, one of which is almost
completely occupied by guest bpy, while in the second one guest water
molecules are present. This compound also shows a reversible, thermally
induced, single-crystal-to-single-crystal transition
A new copper(I) coordination polymer from 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine: Synthesis, characterization, and use as additive in transparent submicron UV filters
<p>The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu<sub>2</sub>(<i>μ</i> − I)<sub>2</sub>(<i>μ</i> − <b>L</b>)<sub>2</sub>]<sub><i>n</i></sub>, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.</p
[OSSO]-Type Iron(III) Complexes for the Low-Pressure Reaction of Carbon Dioxide with Epoxides: Catalytic Activity, Reaction Kinetics, and Computational Study
The
selective conversion of variously substituted epoxides into
the corresponding cyclic carbonates under mild reaction conditions
was achieved with mononuclear FeÂ(III) complexes bearing bis-thioether-diphenolate
[OSSO]-type ligands, in combination with tetrabutylammonium bromide
(TBAB). For example, propylene carbonate was obtained in 1 h at 35
°C (turnover frequency, TOF = 290 h<sup>–1</sup>), from
propylene oxide and 1 bar of CO<sub>2</sub> pressure, using 0.1 mol
% of the FeÂ(III) complex and 0.5 mol % of TBAB. Product divergence
is observed only for cyclohexene oxide toward the exclusive formation
of the aliphatic polycarbonate (TOF = 165 h<sup>–1</sup> at
80 °C and 1 bar of CO<sub>2</sub> pressure, using 0.1 mol % of
the FeÂ(III) complex and 0.1 mol % of tetrabutylammonium chloride).
Kinetic investigations indicated reaction orders of two and one, with
respect to the FeÂ(III) complex, for the production of propylene carbonate
and the polyÂ(cyclohexene carbonate), respectively. The enthalpy and
entropy of activation were determined using the Eyring equation [for
propylene carbonate: Δ<i>H</i><sup>‡</sup> =
8.4 ± 0.7 kcal/mol and Δ<i>S</i><sup>‡</sup> = −33 ± 3 cal/(mol·K); for polyÂ(cyclohexene carbonate):
Δ<i>H</i><sup>‡</sup> = 11.9 ± 0.3 kal/mol
and Δ<i>S</i><sup>‡</sup> = −36 ±
2.2 cal/(mol·K)]. Supported by density functional theory based
investigations, we propose a mechanistic scenario in which the rate-limiting
step is the bimetallic ring opening of the epoxide, in the case of
propylene carbonate, and the monometallic insertion of the epoxide
in the growing polymer chain, in the case of polyÂ(cyclohexene carbonate)
Coordination Polymers Based on the Trinuclear Triangular Secondary Building Unit [Cu<sub>3</sub>(μ<sub>3</sub>‑OH)(μ-pz)<sub>3</sub>]<sup>2+</sup> (pz = pyrazolate) and Succinate Anion
Reaction conditions (solvent, temperature, pressure)
and reagents
ratios control the formation of different products from the reactions
involving Cu<sup>II</sup>, pyrazole (Hpz), and succinate ion (Suc).
Three different coordination polymers (CPs) (one of which porous)
based on the trinuclear triangular Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub> secondary building unit (SBU), as well
as a 1D CP based on the CuÂ(Hpz)<sub>2</sub> SBU were obtained. Moreover,
a 3D supramolecular network, formed through quite strong H-bonding
interactions involving the mononuclear CuÂ(HSuc)<sub>2</sub>(Hpz)<sub>4</sub> complex, was also synthesized when an excess of H<sub>2</sub>Suc was added
Coordination Polymers Based on the Trinuclear Triangular Secondary Building Unit [Cu<sub>3</sub>(μ<sub>3</sub>‑OH)(μ-pz)<sub>3</sub>]<sup>2+</sup> (pz = pyrazolate) and Succinate Anion
Reaction conditions (solvent, temperature, pressure)
and reagents
ratios control the formation of different products from the reactions
involving Cu<sup>II</sup>, pyrazole (Hpz), and succinate ion (Suc).
Three different coordination polymers (CPs) (one of which porous)
based on the trinuclear triangular Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub> secondary building unit (SBU), as well
as a 1D CP based on the CuÂ(Hpz)<sub>2</sub> SBU were obtained. Moreover,
a 3D supramolecular network, formed through quite strong H-bonding
interactions involving the mononuclear CuÂ(HSuc)<sub>2</sub>(Hpz)<sub>4</sub> complex, was also synthesized when an excess of H<sub>2</sub>Suc was added
Coordination Polymers Based on the Trinuclear Triangular Secondary Building Unit [Cu<sub>3</sub>(μ<sub>3</sub>‑OH)(μ-pz)<sub>3</sub>]<sup>2+</sup> (pz = pyrazolate) and Succinate Anion
Reaction conditions (solvent, temperature, pressure)
and reagents
ratios control the formation of different products from the reactions
involving Cu<sup>II</sup>, pyrazole (Hpz), and succinate ion (Suc).
Three different coordination polymers (CPs) (one of which porous)
based on the trinuclear triangular Cu<sub>3</sub>(μ<sub>3</sub>-OH)Â(μ-pz)<sub>3</sub> secondary building unit (SBU), as well
as a 1D CP based on the CuÂ(Hpz)<sub>2</sub> SBU were obtained. Moreover,
a 3D supramolecular network, formed through quite strong H-bonding
interactions involving the mononuclear CuÂ(HSuc)<sub>2</sub>(Hpz)<sub>4</sub> complex, was also synthesized when an excess of H<sub>2</sub>Suc was added