A new triphenylene-imine (ImH) and its ortho-palladated complexes (μ-X)2Pd2Im2 (X = CH3COO–, Cl–, Br–), (μ-Cl)(μ-SC n H2n+1)Pd2Im2 (n = 6, 12), PdIm(acac) PdIm Cl(CNC6H4OC12H25), ...PdImCl(CNC6H3(OC12H25)2), and PdImCl(CNC6H2(OC12H25)3) have been prepared. The free imine ligand is not a liquid crystal, but most ortho-metalated dinuclear palladium complexes and the mononuclear trialkoxyphenyl isocyanide derivative display columnar mesophases at temperatures close to ambient. For the dimeric complexes the mesophase obtained is always columnar rectangular (Colr), with an uncommon structure: the dimeric triphenylene–Pd complex–triphenylene molecules give rise to a triple-column stacking consisting of two columns of stacked triphenylene groups connected to a central column formed by stacking of two ortho-palladated dimeric moieties. For the trialkoxyphenyl isocyanide derivative a related polymer-like arrangement of columns alternating stacking of triphenylenes with stacking of two ortho-palladated dimeric moieties is found. The mesophase structure is columnar oblique (Colob). The free imine and all palladium complexes exhibit fluorescence at room temperature in dichloromethane solution, associated with the triphenylene core.
Gold nanoparticles (Au NPs) have been synthesized using simple thermolysis, whether from the mesophase or from toluene solutions, of mesogenic alkynyl–isocyanide gold complexes Au(CC–C6H4–C m ...H2m+1)(CN–C6H4–O–C n H2n+1). The thermal decomposition from the mesophase is much slower than from solution and produces a more heterogeneous size distribution of the nanoparticles. Working in toluene solution, the size of nanoparticles can be modulated from ∼2 to ∼20 nm by tuning the chain lengths of the ligands present in the precursor. Different experimental conditions have been analyzed to reveal the processes governing the formation of the gold nanoparticles. Experiments on the effect of adding ligands or bubbling oxygen support that the thermal decomposition is a bimolecular process that starts by decoordination of the isocyanide ligand, producing an oxidative coupling of the akynyl group to R–CC–CC–R and reduction of gold(I) to gold(0) as nanoparticles. The nanoparticles obtained behave as a catalyst in the oxidation of isocyanide (CNR) to isocyanate (OCNR), which in turn cooperates to catalyze the decomposition.
Supramolecular metal complexes formed through hydrogen bonding between tris(3,4,5-decyloxy)stilbazole and several metallo-organic acids of the type Au(R)(CNC
6
H
4
CO
2
H) (R = C
6
F
5
, C
6
F
4
OC
...10
H
21
),
cis
-MCl
2
(CNC
6
H
4
COOH)
2
and
trans
-MI
2
(CNC
6
H
4
COOH)
2
(M = Pd, Pt) have been synthesized. All the supramolecular palladium and platinum polycatenar aggregates display a hexagonal columnar mesophase at temperatures close to room temperature. Most of the supramolecular trisalkoxystilbazole complexes exhibit luminescent behaviour. Aggregates of Au(C
6
F
4
OC
10
H
21
)(CNC
6
H
4
CO
2
H) and
trans
-MI
2
(CNC
6
H
4
COOH)
2
(M = Pd, Pt) form stable Langmuir films at the air-water interface.
Supramolecular complexes formed through hydrogen bonding between tris(3,4,5-decyloxy)stilbazole and various metallo-organic acids have been synthesized, revealing the potential of this system to build functional liquid crystals and Langmuir films.
Gold complexes of 4-isocyanobenzoic acid, AuX(CNC(6)H(4)CO(2)H) (X = Ctriple bondC-C(6)H(4)-C(9)H(19), C(6)F(5), C(6)F(4)OC(6)H(13), C(6)F(4)C(6)F(4)Br) and ...(mu-4,4'-C(6)F(4)C(6)F(4)){Au(CNC(6)H(4)CO(2)H)}(2), have been isolated. These metallo-acids are luminescent. The single crystal X-ray diffraction study of Au(C(6)F(5))(CNC(6)H(4)CO(2)H)(infinity) confirms a rod-like structure of the molecule, with a linear coordination around the gold atom, which extends into a supramolecular entity supported by hydrogen bond, gold-gold, and fluorophilic (F(ortho) ... F(meta)) interactions. The carboxylic acid group of the gold isocyanide complexes acts also as a hydrogen donor towards the hydrogen acceptor decyloxystilbazole, affording some hydrogen-bonded supramolecular liquid crystals.
Displacement of a labile ligand from appropriate precursor complexes by 2- or 4-PPh2C6H4COOH yields neutral gold(I) and gold(III) AuX n (PPh2C6H4COOH) (n = 1, X = Cl; n = 3, X = C6F5), cationic ...gold(I) Au(PPh2C6H4COOH)2(CF3SO3), and neutral chromium(0) Cr(CO)5(PPh2C6H4COOH) metallo–organic acids. AuCl(4-PPh2C6H4COOH), Au(C6F5)3(4-PPh2C6H4COOH), and Cr(CO)5(2-PPh2C6H4COOH) have dimeric structures with typical carboxylic H-bond bridges, whereas Au(C6F5)3(2-PPh2C6H4COOH) gives a monomeric species with the carboxylic acid H bonded to cocrystallized solvent molecules. All gold-containing acids are emissive at 77 K in the range 404–520 nm and some of them also at 298 K with emission maxima from 441 to 485 nm. Reaction of these acid metal complexes with the triazine mesogen 2,4,6-{(C10H21O)3C6H2NH}3C3N3 affords some new hydrogen-bonded gold(I) and chromium(0) supramolecular adducts, but the related gold(III) complexes do not form adducts. The 4-diphenylphosphinobenzoic adducts display a columnar hexagonal mesophase (Colhex) at room temperature, with a random one-dimensional stacking of the pseudo-discoid triazine–metallo–organic adducts into columns, where the metallo–phosphinoacid fragments act as the fourth branch of the trifold triazine core. The 2-diphenylphosphinobenzoic mixtures do not display mesophases, as they appear in the X-ray studies as mixtures of the triazine and the metallo–phosphinoacid complex. The aggregates are luminescent at 77 K, with emission maxima in the range 419–455 nm.
Hybrid organic−inorganic supramolecular aggregates displaying liquid crystal properties at room temperature have been synthesized by linking equimolar amounts of 2,4,6-triarylamino-1,3,5-triazine and ...metallo-acids Fe(CO)4(CNC6H4CO2H) and M(CO)5(CNC6H4CO2H) (M = Cr, Mo, W) through hydrogen bonding formation. The starting metalloacids and their triazine aggregates display photoluminescent properties in solution and in the condensed phase (crystalline or glassy) at low temperature, but not in the mesophase. The mesophase produced by the supramolecular hybrid aggregates is always columnar hexagonal (Colh), corresponding to a columnar packing of 1:1 triazine-metalloacid supramolecules. The stability range of the columnar hexagonal mesophases is large, and the clearing temperatures decrease very regularly in the order Fe > Cr > Mo > W. All the supramolecular species show high thermal stability, even in the isotropic state.
Several salen manganese(III) complexes displaying stable columnar mesophases in a wide range of temperatures have been synthesized. In condensed phases the molecules are assembled into dimers through ...intermolecular manganese-oxygen interactions and the columnar structure of the mesophases consist of the stacking of supramolecular discs formed by the association of two or three dimers, depending on the number and location of alkoxy chains in the complex. The catalytic activity of the complexes in solution has been studied, and they behave as efficient homogeneous catalysts in the epoxidation of styrene with iodosylbenzene as oxidant.
Gold nanoparticles have been deposited on three kinds of carbon nanotubes (CNTs), including nitrogen‐doped CNTs, by three different methods, namely, impregnation, organometallic decomposition, and ...deposition–precipitation. The choice of the gold precursor, the support, and the preparation procedure is critical for the control of the size and location (on or inside the nanotubes) of the gold nanoparticles. These catalysts were tested for the selective oxidation of CO in a hydrogen‐rich atmosphere. We have shown that the use of nitrogen‐doped CNTs as a support permits one to reach much higher activity and selectivity at low temperaturethan with the other CNT supports. This catalyst also shows a good stability under reaction conditions without detectable sintering.
Gold nanoparticles have been selectively deposited on or inside different types of carbon nanotubes by using various synthetic strategies. The catalytic systems prepared on nitrogen‐doped nanotubes show promising activity and selectivity for the selective oxidation of CO in a hydrogen‐rich atmosphere.
The second harmonic generations of the dimeric complexes M2(μ-X)(μ-SC n H2 n +1)(RC6H3CHNC6H4R‘) (M = Pd, Pt; X = Cl, CH3COO, (R)-CH3CHClCOO; R, R‘ = NO2 and OC8H17 or N(C4H9)2; n = 4 or 8) and the ...monomeric complexes Pd(RC6H3CHNC6H4R‘)L (L = C5H5 (Cp), CH3COCHCOCH3 (acac)) and Pd(RC6H3CHNC6H4R‘)(CNC6H4R‘‘)Cl (R‘‘ = NO2, OC n H2 n +1, N(C m H2 m +1)2; n = 4 or 8; m = 1 or 4) have been measured, and the influence of the position of donor and acceptor groups is discussed and compared with that of the free imine ligands. The value of the hyperpolarizability (β) is raised only when a strong donor group is located in the cyclometalated ring. Moreover, the β value has been enhanced, too, in the cyclopentadienyl monomer complex by as much as 80% with respect to the β value of the corresponding free imine. The molecular structure of Pd2(μ-Cl)(μ-SC4H9)(N(C4H9)2C6H3CHNC6H4NO2 has been determined by an X-ray diffraction analysis.
A new triphenylene-isocyanide CN-C 6 H 4 -O-(CH 2 ) 6 -TriPh, non mesogenic, and their ortho -metallated benzoquinolate (bzq) complexes, M(bzq)X(CN-C 6 H 4 -O-(CH 2 ) 6 -TriPh) (M = Pd, Pt; X = Cl, ...I) and Pt(bzq)(CN-C 6 H 4 -O-(CH 2 ) 6 -TriPh) 2 A (A = NO 3 − , BF 4 − , PF 6 − ), all displaying a columnar mesophase, have been prepared. The structure of the mesophase, determined by X-ray diffraction methods, is uncommon and consists of a central column formed by stacking of the organometallic benzoquinoline-platinum fragments, surrounded by six columns in hexagonal disposition formed by stacking of the triphenylene groups. These materials show aggregation-induced phosphorescence based on inter-disk Pt⋯Pt interactions.
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