Sintesi e studio fotofisico di sistemi Eu@POSS: controllo dell’emissione attraverso isomeria cis-trans.

Light-induced trans-cis isomerization of terpyridine functionalized POSS nanostructures self-assembled in presence of Eu3+ ions

Cover Feature: Tuneable Emission of Polyhedral Oligomeric Silsesquioxane Based Nanostructures that Self‐Assemble in the Presence of Europium(III) Ions: Reversible trans ‐to‐ cis Isomerization (ChemPlusChem 3/2020)

White light emitting silsesquioxane based materials: the importance of a ligand with rigid and directional arms

The synthesis of a novel polyhedral oligomeric silsesquioxane functionalized with eight rigid and directional terpyridine-based arms (Ter-POSS) was successfully achieved via a Sonogashira reaction. The POSS based ligand was extensively characterized using different techniques including 1H, 13C and 29Si NMR as well as UV-Vis and fluorescence spectroscopies. The assembly of these nano-caged units in the presence of different transition metal ions (Fe2+, Zn2+ and Cu2+) as well as of a cation from the lanthanides (Eu3+) was investigated using absorption and emission spectroscopies. The final materials display an evident emission in different regions of the visible spectrum as a function of the …

Imidazolium-Functionalized Carbon Nanohorns for the Conversion of CO2 Unprecedented Increase of Catalytic Activity after Recycling

Carbon nanohorns (CNHs) were selected as a novel catalytic platform for the design of imidazolium based hybrid materials able to promote the conversion of carbon dioxide into cyclic carbonates. Several heterogeneous catalysts were prepared using a one-step procedure based on the radical polymerization of various bis-vinylimidazolium salts in the presence of pristine CNHs. The as-synthesized materials were tested for the fixation of CO2 into epoxides. The excellent catalytic performances were evaluated in terms of turnover number and productivity. The versatility of the above hybrids was proved using several epoxides as substrate. Catalysts recyclability was successfully verified for several…

Imidazolium-Functionalized Carbon Nanohorns for the Conversion of Carbon Dioxide

Six new hybrid materials composed of carbon nanohorns (CNHs) and highly cross-linked imidazolium salts were easily synthesized using a one-step procedure based on the radical oligomerization of bis-vinylimidazolium salts (bVImiX) in the presence of pristine CNHs. The hybrid materials were characterized and employed as the sole catalysts for the conversion of carbon dioxide into cyclic carbonate by reaction with epoxides. The solids displayed excellent turnover number and productivity. Moreover, four catalysts were investigated in recycling experiments. Two catalysts containing an octyl linker between the imidazolium units and a bromide or an iodide anion showed no loss in activity after thr…

Ship-in-a-Bottle Synthesis of a Large Guest Occupying Two Y Zeolite Neighbour Supercages: Characterisation and Photocatalytic Activity of the Encapsulated Bipyrylium Ion

In a series of papers we reported the ship-in-a-bottle synthesis, photochemical properties and photocatalytic applications of 2,4,6-triphenylpyrylium cation (TP ) encapsulated inside the cavities of large pore zeolites Y and Beta. 2] The identity of encapsulated TP was then confirmed spectroscopically, particularly by the match of the IR spectra of the encapsulated organic material and that of the tetrafluoroborate solid of TP (TPBF4). In addition, the electrochemical response of zeolite Y encapsulated TP (TP@Y) consisted of a reversible single reduction process taking place at the same redox potential as that measured for TPBF4 solutions. Encapsulation of TP has a dramatic influence on its…

Study of Redox Processes in Zeolite Y-Associated 2,4,6-Triphenylthiopyrylium Ion by Square Wave Voltammetry

The electrochemical responses of 2,4,6-triphenylthiopyrylium ion (TTP+) in solution and attached to zeolite Y (TTP@Y) are described using cyclic and square wave voltammetries upon immersion of zeolite-modified polymer film electrodes in MeCN (LiClO4, Et4NClO4, and BuN4PF6 electrolytes) and aqueous (LiNO3, NaNO3, and KNO3 electrolytes) media. The electrochemistry of TTP@Y in contact with Bu4NPF6/MeCN is identical to that of TTP(BF4) in solution, with reduction processes at −0.25, −0.74, and −1.36 V vs SCE, and oxidation steps at +0.85 and +1.11 V. This response differs from those obtained for TTP@Y in Et4NClO4/MeCN and LiClO4/MeCN electrolytes. In contact with aqueous electrolytes, TTP@Y dis…

Electro- and magneto-electrochemistry of zeolite Y- and MCM-41-associated bipyrylium ion

Abstract The electrochemical response of bipyrylium bication [1,4-bis(3,5-diphenyl-4-pyrylium)phenylene] associated with Y and MCM-41 aluminosilicates (BTP@Y and BTP@MCM, respectively) is described using polymer-film electrodes immersed into Et 4 N +  + MeCN and Bu 4 N +  + MeCN electrolytes. BTP@MCM provides a solution-like response in all electrolytes consisting in two successive strongly comproportionation mediated one-electron reduction processes near to +0.05 and −0.12 V vs. Ag|AgCl. The response of BTP@Y in Bu 4 N +  + MeCN is restricted to a unique reduction process near to −0.40 V, while in Et 4 N +  + MeCN, it differs significantly: here, two reduction processes at −0.22 and −0.36 …

Catalizzatori a base di nanocorni di carbonio-liquidi ionici per la conversione della CO2

Nel presente lavoro sono stati impiegati nanocorni di carbonio (CNHs) come piattaforma catalitica per il design di nuovi materiali ibridi a base di sali di imidazolio per la conversione della CO2 in carbonati ciclici. A tale scopo sono stati preparati una serie di catalizzatori eterogenei mediante una procedura sintetica one-pot basata sulla polimerizzazione radicalica di vari sali di bis vinilimidazolio in presenza di nanocorni di carbonio. I suddetti materiali sono stati caratterizzati e testati con successo per la reazione di fissazione della CO2 in epossidi (Figura 1). Figura 1 Conversione della CO2 catalizzata da liquidi ionici supportati su CNHs Le performances catalitiche, valutate i…

Boehmite Supported Pyrene Polyamine Systems as Probes for Iodide Recognition

New organic–inorganic fluorescent probes made by attaching the tripodal polyamine (tris(2-aminoethyl))amine (tren), propylamine, or diethylenetriamine functionalized with pyrene as a fluorophore to an γ-aluminum oxohydroxide matrix have been prepared and studied both in solution and supported on the surface of boehmite nanoparticles. Both kinds of systems have been revealed as sensitive and selective fluorescence turn-off chemosensors for iodide in aqueous solution with an estimated detection limit that reaches 36 ppb. The recognition characteristics and photophysical properties of these molecules are essentially preserved when they are grafted to the surface of the particles. Since the nan…

Tuneable Emission of Polyhedral Oligomeric Silsesquioxane Based Nanostructures that Self-Assemble in the Presence of Europium(III) Ions: Reversible trans-to-cis Isomerization

[EN] Hybrid nanostructures with switchable and reversible "blue-red-green" emission were efficiently synthesized. These nanostructures comprise polyhedral oligomeric silsesquioxanes (POSS) that behave as a nanocage that can be functionalized with terpyridine-based organic ligands, which can be easily complexed with europium (III) ions. The complexes were characterized by UV-Vis and fluorescence spectroscopy and their stoichiometry was also confirmed by H-1 NMR spectroscopy. In the presence of the Eu(III) ions, the octafunctionalized nanocages self-assemble to form 3D architectures that display an intense red-emission, especially in the solid state. The presence of an alkenyl group bridging …

Proximity Effect using a Nanocage Structure: Polyhedral Oligomeric Silsesquioxane-Imidazolium Tetrachloro- palladate Salt as a Precatalyst for the Suzuki-Miyaura Reaction in Water

A polyhedral oligomeric silsesquioxane-imidazolium tetrachloropalladate salt (POSS-Imi-PdCl4) was prepared by the reaction of a polyhedral oligomeric silsesquioxane-imidazolium chloride salt (POSS-Imi-Cl) with PdCl2 and used as a pre-catalyst for the Suzuki-Miyaura reaction in water at 100 °C at a low loading (0.08-0.16 mol %). Biphenyl compounds were isolated in high to excellent yields. A comparison of the POSS-based catalyst with the corresponding catalyst without the nanocage structure (i.e., 1-butyl-3-methylimidazolium tetrachloropalladate) highlighted the role of the POSS structure to reach higher yields in the Suzuki-Miyaura reaction. This result is ascribed to a proximity effect of …

Molecular recognition of nucleotides in water by scorpiand-type receptors based on nucleobase discrimination.

Abstract: The detection of nucleotides is of crucial impor-tance because they are the basic building blocks of nucleicacids. Scorpiand-based polyamine receptors functionalizedwith pyridine or anthracene units are able to form stablecomplexes with nucleotides in water, based on coulombic,p–p stacking, and hydrogen-bonding interactions. This be-havior has been rationalized by means of an explorationwith NMR spectroscopy and DFT calculations. Binding con-stants were determined by potentiometry. Fluorescencespectroscopy studies have revealed the potential of these re-ceptors as sensors to effectively and selectively distinguishguanosine-5’-triphosphate (GTP) from adenosine-5’-triphos-phate (ATP…