Giuliano Giambastiani

Amine-Templated Polymeric Lanthanide Formates: Synthesis, Characterization, and Applications in Luminescence and Magnetism

The novel polymeric formates of general formula [(Fmd)Ln(III)(HCOO)(4)](∞) (Fmd(+) = NH(2)-CH(+)-NH(2); Ln = Eu (1), Gd (2), Tb (3), Dy (4)] were synthesized through solvothermal methods in formamide solutions. The compounds are isotructural; they crystallize in the orthorhombic C222(1) chiral space group. The coordination geometry at the metal centers is square antiprismatic (coordination number eight), with each formate ligand bridging adjacent lanthanide ions. The overall negative three-dimensional (3D) framework charge is balanced by the formamidinium cations sitting inside the channels along the a axis, forming extensive N-H···O hydrogen bonding with the surrounding cage. All the compounds have been characterized through single-crystal/powder X-ray diffraction, IR spectroscopy, and TG-MS analysis. Finally, their luminescence and magnetic properties have been assessed, leading to remarkable emission intensities, especially for the Tb(III) compound (Φ = 0.83), with corresponding lifetime decays in the micro (Dy) and millisecond (Tb, Eu) time scale. A weak but sizable antiferromagnetic interaction has been observed for the Gd(III) derivative.

Renewable H2 from Glycerol Steam Reforming: Effect of La2O3 and CeO2 Addition to Pt/Al2O3 catalysts.

Glycerol is the main byproduct of biodiesel production and its increased production volume derives from the increasing demand for biofuels. The conversion of glycerol to hydrogen-rich mixtures presents an attractive route towards sustainable biodiesel production. Here we explored the use of Pt/Al(2)O(3)-based catalysts for the catalytic steam reforming of glycerol, evidencing the influence of La(2)O(3) and CeO(2) doping on the catalyst activity and selectivity. The addition of the latter metal oxides to a Pt/Al(2)O(3) catalyst is found to significantly improve the glycerol steam reforming, with high H(2) and CO(2) selectivities. A good catalytic stability is achieved for the Pt/La(2)O(3)/Al(2)O(3) system working at 350 degrees C, while the Pt/CeO(2)/Al(2)O(3) catalyst sharply deactivates after 20 h under similar conditions. Studies carried out on fresh and exhausted catalysts reveal that both systems maintain high surface areas and high Pt dispersions. Therefore, the observed catalyst deactivation can be attributed to coke deposition on the active sites throughout the catalytic process and only marginally to Pt nanoparticle sintering. This work suggests that an appropriate support composition is mandatory for preparing high-performance Pt-based catalysts for the sustainable conversion of glycerol into syngas.

Poly(lactic acid) as a transparent matrix for luminescent solar concentrators: a renewable material for a renewable energy technology

The suitability of L-poly(lactic acid) (L-PLA) as a transparent matrix, alternative to poly(methylmetacrilate) (PMMA), for use in luminescent solar concentrators is herein demonstrated. Low molecular weight L-PLA-based films, both chemically modified or blended with an oligothiophene luminescent dye (T5OH), showed excellent processability, photostability, and exhibited fluorescence quantum yields (of about 35%) even higher than T5OH-doped PMMA.

Facing Unexpected Reactivity Paths with ZrIV–Pyridylamido Polymerization Catalysts

This work provides original insights to the better understanding of the complex structure-activity relationship of Zr(IV)-pyridylamido-based olefin polymerization catalysts and highlights the importance of the metal-precursor choice (Zr(NMe(2))(4) vs. Zr(Bn)(4)) to prepare precatalysts of unambiguous identity. A temperature-controlled and reversible σ-bond metathesis/protonolysis reaction is found to take place on the Zr(IV)-amido complexes in the 298-383 K temperature range, changing the metal coordination sphere dramatically (from a five-coordinated tris-amido species stabilized by bidentate monoanionic {N,N(-)} ligands to a six-coordinated bis-amido-mono-amino complexes featured by tridentate dianionic {N(-),N,C(-)} ligands). Well-defined neutral Zr(IV)-pyridylamido complexes have been prepared from Zr(Bn)(4) as metal source. Their cationic derivatives [Zr(IV) N(-),N,C(-)}Bn](+)[B(C(6)F(5))(4)](-) have been successfully applied to the room-temperature polymerization of 1-hexene with productivities up to one order of magnitude higher than those reported for the related Hf(IV) state-of-the-art systems. Most importantly, a linear increase of the poly(1-hexene) M(n) values (30-250 kg mol(-1)) has been observed upon catalyst aging. According to that, the major active species (responsible for the increased M(n) polymer values) in the aged catalyst solution, has been identified.

Photothermally Activated Hybrid Films for Quantitative Confined Release of Chemical Species

Illuminating films of a porous chitosan matrix containing gold nanorods and thermosensitive micelles loaded with a chemical stimulates local photothermal conversion of the gold nanorods. The heat produced activates the ejection of the chemical from the micelles (see scheme), and causes the transient permeabilization of adjacent cell membranes, resulting in a selective cellular uptake of the released chemical with control over spatiotemporal parameters and dosage.

Metal-to-Ligand Alkyl Migration Inducing Carbon–Sulfur Bond Cleavage in Dialkyl Yttrium Complexes Supported by Thiazole-Containing Amidopyridinate Ligands: Synthesis, Characterization, and Catalytic Activity in the Intramolecular Hydroamination Reaction

Neutral Y(III) dialkyl complexes supported by tridentate N(-) ,N,N monoanionic methylthiazole- or benzothiazole-amidopyridinate ligands have been prepared and completely characterized. Studies on their stability in solution revealed progressive rearrangement of the coordination sphere in the benzothiazole-containing system through an unprecedented metal-to-ligand alkyl migration and subsequent thiazole ring opening. Attempts to synthesize hydrido species from the dialkyl precursor led to the generation of a dimeric yttrium species stabilized by a trianionic N(-) ,N,N(-) ,S(-) ligand as the result of metal-to-ligand hydride migration with chemoselective thiazole ring opening and subsequent dimerization through intermolecular addition of the residual YH group to the imino fragment of a second equivalent of the ring-opened intermediate. DFT calculations were used to elucidate the thermodynamics and kinetics of the process, in support of the experimental evidence. Finally, all isolated yttrium complexes, especially their cationic forms prepared by activation with the Lewis acid Ph3 C(+) [B(C6 F5 )4 ](-) , were found to be good candidate catalysts for intramolecular hydroamination/cyclization reactions. Their catalytic performance with a number of primary and secondary amino alkenes was assessed.

Amine-templated polymeric Mg formates: crystalline scaffolds exhibiting extensive hydrogen bonding

Two novel polymeric Mg formates [(Fmd)Mg(HCOO)3]∞ (1) and [(Gua)Mg(HCOO)3]∞ (2) containing the formamidinium [Fmd+, (NH2–CH+–NH2)] and guanidinium [Gua+, C+(NH2)3] cations have been prepared under solvothermal conditions. 1 and 2 are isostructural; they crystallize in the orthorhombic space group Pnna. Their 3D scaffolds consists of Mg ions in an octahedral coordination environment bridged by formate ligands. The overall framework charge is negative, and the cations are located in the centre of the lattice cavities, forming extensive N–H⋯O hydrogen bonding with the surrounding cage. Both compounds have been characterized through single-crystal and powder X-ray diffraction, 1D and 2D solid-state NMR (1H, 13C and 15N), IR spectroscopy and TG-MS analysis. Their chemical reactivity towards ion exchange and ability as CO2 storage materials has been finally examined.

Pd(0)-catalyzed allylic alkylation/Heck coupling in domino sequence ☆

Abstract A new molecular queuing process has been achieved, in which a single Pd-based catalytic system promotes two unrelated, sequential catalytic cycles in chronologically distinct order. This study demonstrates also that allylic alkylations can be catalyzed by the Herrmanns phosphapalladacycle, a result that further supports the involvement of a Pd(0) species in its mechanism of action.

“Click” on Tubes: a Versatile Approach towards Multimodal Functionalization of SWCNTs

Organic functionalization of carbon nanotube sidewalls is a tool of primary importance in material science and nanotechnology, equally from a fundamental and an applicative point of view. Here, an efficient and versatile approach for the organic/organometallic functionalization of single-walled carbon nanotubes (SWCNTs) capable of imparting multimodality to these fundamental nanostructures, is described. Our strategy takes advantage of well-established Cu-mediated acetylene-azide coupling (CuAAC) reactions applied to phenylazido-functionalized SWCNTs for their convenient homo-/heterodecoration with a number of organic/organometallic frameworks, or mixtures thereof, bearing terminal acetylene pendant arms. Phenylazido-decorated SWCNTs were prepared by chemoselective arylation of the CNT sidewalls with diazonium salts under mild conditions, and subsequently used for the copper-mediated cycloaddition protocol in the presence of terminal acetylenes. The latter reaction was performed in one step by using either single acetylene derivatives or equimolar mixtures of terminal alkynes bearing either similar functional groups (masked with orthogonally cleavable protecting groups) or easily distinguishable functionalities (on the basis of complementary analytical/spectroscopic techniques). All materials and intermediates were characterized with respect to their most relevant aspects/properties by TEM microscopy, thermogravimetric analysis coupled with MS analysis of volatiles (TG-MS), elemental analysis, cyclic voltammetry (CV), Raman and UV/Vis spectroscopy. The functional loading and related chemical grafting of both primary amino- and ferrocene-decorated SWCNTs were spectroscopically (UV/Vis, Kaiser test) and electrochemically (CV) determined, respectively.

Synthesis, characterization and CO2 uptake of a chiral Co(II) metal–organic framework containing a thiazolidine-based spacer

The polytopic ligand thiazolidine-2,4-dicarboxylic acid (H2L) has been synthesised on a large scale starting from the naturally occurring amino acid L-cysteine. The (R,R)/(S,R)diastereomeric mixture has been separated into its constituents through selective precipitation of the pure (R,R) isomer from concentrated H2O/MeOH solutions. The enantiomerically pure ligand (H2L-RR) has been reacted with CoCl2·6H2O under hydrothermal conditions, with the final product being [Co(L-RR)(H2O)·H2O]∞ (1). The obtained coordination polymer is optically pure, and it maintains the chiral information that is present in its building block. Two different kinds of channels are present in the 3D structure of 1: one hydrophobic (with the sulfur atoms of the thiazolidine rings exposed) and the other hydrophilic [with the aquo ligand on Co(II) exposed, and hosting the crystallization water solvent]. 1 has been characterized through a combination of X-ray diffraction (single-crystal and powder) and spectroscopic (CD, IR, UV-Vis, XANES, EXAFS) techniques. Finally, CO2 adsorption tests conducted at 273 K and (pCO2)max = 920 torr have shown a good carbon dioxide uptake, equal to 4.7 wt%.