Self-Assembly of Supramolecular Double Helix from a Tetrapeptide and Direct Visualization by Scanning Tunneling Microscopy.

This work reports single-crystal X-ray diffraction (XRD), Scanning Tunneling Microscopy (STM), and quantum mechanics calculations of the 3-helical peptide Z-(Aib)-L-Dap(Boc)-Aib-NHiPr (Aib, α-aminoisobutyric acid; Dap, 2,3-diaminopropionic acid; Z, benzyloxycarbonyl; Boc, t-butoxycarbonyl). The peptide forms a double-helical superstructure, studied by XRD and STM. Such architecture is rare in short peptides.

Ion-Pairing Stereodynamic Probes for Circular Dichroism Chiral Sensing of Amines.

Tris(2-pyridylmethyl)amine () and tris(2-phenolmethyl)amine () metal complexes have been extensively used for catalysis and molecular recognition applications. In particular, due to their ability to form stereodynamic complexes through the helical arrangement of the ligand around the metal in a propeller shape, chiroptical sensing has been extensively investigated. In particular, the capability of the analyte, usually a Lewis base, to bind the metal complex has been the predominant recognition motif.

Mononuclear Rare-Earth Metalloligands Exploiting a Divergent Ligand.

Rare-earth tris-diketonato [RE(dike)pyterpy] metalloligands can be prepared reacting at room temperature [RE(dike)dme] (dme = 1,2-dimethoxyethane; dike = tta with Htta = 2-thenoyltrifluoroacetone and RE = La, ; Y, ; Eu, ; Dy, ; or dike = hfac with Hhfac hexafluoroacetylacetone, and RE = Eu, ; Tb, ; Yb ) with 4'-(4‴-pyridil)-2,2':6',2″-terpyridine (pyterpy). The molecular structures of , , , and have been studied through single-crystal X-ray diffraction showing mononuclear neutral complexes with the rare-earth ion in coordination number nine and with a muffin-like coordination geometry. [RE(tta)pyterpy] promptly reacts with [M(tta)dme] with formation of [Mpyterpy][RE(tta)] (M = Zn, RE = Y, ; M = Co, RE = Dy, ).

Graphene Oxide-Arginine Composites: Efficient Dual Function Materials for Integrated CO Capture and Conversion.

The "on-demand" capture and utilization of CO is effectively realized with a readily accessible dual function organic composite. The covalent and controlled derivatization of graphene oxide (GO) surface with naturally occurring arginine led to a "smart" material capable of capturing (chemisorption) CO from high-purity flue-gas as well as low-concentration streams (i. e.

Supported MOCVD TiO Thin Films Grown on Modified Stainless Steel Mesh for Sensing Applications.

Among semiconductor metal oxides, that are an important class of sensing materials, titanium dioxide (TiO) thin films are widely employed as sensors because of their high chemical and mechanical stability in harsh environments, non-toxicity, eco-compatibility, and photocatalytic properties. TiO-based chemical oxygen demand (COD) sensors exploit the photocatalytic properties of TiO in inducing the oxidation of organic compounds to CO. In this work, we discuss nanostructured TiO thin films grown via low-pressure metal organic chemical vapor deposition (MOCVD) on metallic AISI 316 mesh.

Investigations on Caesium Dispersion and Molybdenum Coating on SPIDER Components.

SPIDER is the 100 keV full-size Negative Ion Source prototype of the ITER Neutral Beam Injector, operating at Consorzio RFX in Padova, Italy. The largest Negative Ion Source in the world, SPIDER generates an RF driven plasma from which Deuterium or Hydrogen negative ions are produced and extracted. At the end of 2021, a scheduled long-term shutdown started to introduce major modifications and improvements aiming to solve issues and drawbacks identified during the first three years of SPIDER operations.

Helicate versus Mesocate in Quadruple-Stranded Lanthanide Cages: A Computational Insight.

To drive the synthesis of metallo-supramolecular assemblies (MSAs) and to fully exploit their functional properties, robust computational tools are crucial. The capability to model and to rationalize different parameters that can influence the outcome is mandatory. Here, we report a computational insight on the factors that can determine the relative stability of the supramolecular isomers helicate and mesocate in lanthanide-based quadruple-stranded assemblies.

Carbodiimide-Mediated Beckmann Rearrangement of Oxyma-B as a Side Reaction in Peptide Synthesis.

The suppression of side reactions is one of the most important objectives in peptide synthesis, where highly reactive compounds are involved. Recently, the violuric acid derivative Oxyma-B was introduced into peptide synthesis protocols as a promising additive to efficiently control the optical purity of the amino acids prone to racemization. However, we discovered a side reaction involving the Beckmann rearrangement of Oxyma-B during the coupling reaction, which compromises the yield and purity of the target peptides.

Origin of the Unusual Ground-State Spin = 9 in a Cr Single-Molecule Magnet.

The molecular wheel [Cr(OMe)(OCCMe)], abbreviated {Cr}, with an unusual intermediate total spin = 9 and non-negligible cluster anisotropy, / = -0.045(2) K, is a rare case among wheels based on an even number of 3d-metals, which usually present an antiferromagnetic (AF) ground state ( = 0). Herein, we unveil the origin of such a behavior.

Nature of the Ligand-Centered Triplet State in Gd β-Diketonate Complexes as Revealed by Time-Resolved EPR Spectroscopy and DFT Calculations.

A series of Gd complexes (-) with the general formula GdL(EtOH), where L is a β-diketone ligand with polycyclic aromatic hydrocarbon substituents of increasing size (-), was studied by combining time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy and DFT calculations to rationalize the anomalous spectroscopic behavior of the bulkiest complex () through the series. Its faint phosphorescence band is observed only at 80 K and it is strongly red-shifted (∼200 nm) from the intense fluorescence band. Moreover, the TR-EPR spectral analysis found that triplet levels of / are effectively populated and have smaller || values than those of the other compounds.

Design of a Zn Single-Site Curing Activator for a More Sustainable Sulfur Cross-Link Formation in Rubber.

ZnO is a worldwide used activator for a rubber vulcanization process, which promotes fast curing kinetics and high cross-linking densities of rubber nanocomposites (NCs). However, its extended use together with leaching phenomena occurring during the production and life cycle of rubber products, especially tires, entails potential environmental risks, as ecotoxicity toward aquatic organisms. Pushed by this issue, a novel activator was developed, which introduces highly dispersed and active zinc species in the vulcanization process, reducing the amount of employed ZnO and keeping high the curing efficiency.

Multireference Investigation on Ground and Low-Lying Excited States: Systematic Evaluation of - Mixing in a Eu Luminescent Complex.

A theoretical protocol combining density functional theory (DFT) and multireference (CAS) calculations is proposed for a Eu complex. In the complex, electronic levels of the central Eu ion are correctly calculated at the CASPT2 level of theory, and the effect of introducing different numbers of states in the configuration interaction matrices is highlighted as well as the shortcomings of DFT methods in the treatment of systems with high spin multiplicity and strong spin-orbit coupling effects. For the D state energy calculation, the inclusion of states with different multiplicity and the number of states considered for each multiplicity are crucial parameters, even if their relative weight is different.

Antenna triplet DFT calculations to drive the design of luminescent Ln complexes.

Density functional theory-based methods have been exploited to look into the structural, vibrational and electronic properties of antenna ligands, all of them being crucial factors for the reliable design of customized luminescent lanthanide (Ln3+) complexes. The X-ray structures, UV-Vis absorption spectra and triplet (T1) energies of three novel β-diketone ligands with a thienyl group and naphthyl (L1), phenanthryl (L2), and pyrenyl (L3) polycyclic aromatic hydrocarbons as substituents have been modelled. Vibronic progressions provide a strong contribution to the L1 and L2 absorption spectra, while the L3 absorption spectrum needs the assumption of different conformational isomers in solution.

Light-Triggered Catalytic Asymmetric Allylic Benzylation with Photogenerated -Nucleophiles.

Herein is reported the asymmetric allylic benzylation of Morita-Baylis-Hillman (MBH) carbonates with 2-methylbenzophenone (MBP) derivatives as nonstabilized photogenerated -nucleophiles. The dual activation of both reaction partners, chiral Lewis-base activation of the electrophile and light activation of the nucleophile, enables the stereoselective installation of benzyl groups at the allylic position to forge tertiary and quaternary carbon centers.

Possible Synthetic Approaches for Heterobimetallic Complexes by Using NHC/NHC Heteroditopic Carbene Ligands.

The synthesis of heterobimetallic complexes remains a synthetic challenge in the field of organometallic chemistry. A possible approach in this regard might be the use of a bidentate heteroditopic bis(carbene) ligand that combines an imidazol-2-ylidene (NHC) with a 1,2,3-triazol-5-ylidene (NHC) connected by an organic spacer. The optimized strategy to heterobimetallic complexes with this type of ligand involves a 3-step procedure: (i) Coordination of the NHC, functionalized with a 1,2,3-triazole ring, to a metal center; (ii) formation of the triazolium ring by alkylation of the triazole N-3; (iii) deprotonation of the NHC precursor and coordination of the second metal center.

A Cu(ii) metallocycle for the reversible self-assembly of coordination-driven polyrotaxane-like architectures.

We report the design and synthesis of a Cu(ii) metallocycle (1) and use the possibility to expand the Cu(ii) coordination sphere to self-assemble mechanically interlocked species via interpenetration. Metallocycle 1 can be used as a platform to reversibly assemble a 1D + 1D → 1D coordination-driven polyrotaxane (3), where 1 acts as the hosting ring as well as the stopper, and 4,4'-bipyridine is the guest-axle. A coordinating solvent can substitute the 4,4'-bipyridine axle to disassemble the polyrotaxane (3 → 2) that is easily restored by further adding 4,4'-bipyridine (2 → 3).

Theoretical Investigation of the Electronic Properties of Three Vanadium Phthalocyaninato (Pc) Based Complexes: PcV, PcVO, and PcVI.

The electronic properties of three vanadium phthalocyaninato (Pc) based complexes (PcV, PcVO, and PcVI; I-III, respectively) were theoretically investigated and corresponding L-edge XAS spectra modeled. Ground state (GS) DFT outcomes indicated that II is more stable than III by 141 kcal/mol; moreover, the Ziegler transition state method allowed us to estimate the PcV-X bond dissociation energy and to quantify σ/π contributions to the V-X interaction. As such, the Nalewajski-Mrozek V-X and V-N bond multiplicity indexes (V-O/V-I = 2.

Surface oxidation of single wall carbon nanohorns for the production of surfactant free water-based colloids.

In this work, powders of Single Wall Carbon Nanohorns (SWCNHs), a typical hydrophobic material, were oxidized with concentrated HNO with the aim of surface carboxylation and consequent improved hydrophilicity and dispersibility in polar solvents. Dynamic Light Scattering and ζ-potential measurements demonstrated that very stable colloidal suspensions of SWCNH in water were obtained in total absence of stabilizers. By properly optimizing the reaction parameters, the suspensions achieved stability even higher than colloids with similar composition but prepared with the use of surfactants.

Hybrid Organic/Inorganic Perovskite-Polymer Nanocomposites: Toward the Enhancement of Structural and Electrical Properties.

Hybrid organic/inorganic perovskite nanoparticles (NPs) have garnered remarkable research attention because of their promising photophysical properties. New and interesting properties emerge after combining perovskite NPs with semiconducting materials. Here, we report the synthesis and investigation of a composite material obtained by mixing CHNHPbBr nanocrystals with the semiconducting polymer poly(3-hexylthiophene) (P3HT).

BiOCl/(BiO)CO Nanocomposite Materials for Pollutant Adsorption and Degradation: Modulation of the Functional Properties by Composition Tailoring.

BiOCl/(BiO)CO nanocomposite materials were studied as bifunctional systems for depuration of wastewater. They are able to efficiently adsorb and decompose rhodamine B (RhB) and methyl orange (MO), used as model pollutants. BiOCl/(BiO)CO nanocomposites were synthesized at room temperature and ambient pressure by means of controlled hydrolysis of BiCl in the presence of a surfactant (Brij 76).

A terminally protected dipeptide: from crystal structure and self-assembly, through co-assembly with carbon-based materials, to a ternary catalyst for reduction chemistry in water.

A terminally protected, hydrophobic dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) was synthesized and its 3D-structure was determined by single crystal X-ray diffraction analysis. This peptide is able to hierarchically self-assemble in a variety of superstructures, including hollow rods, ranging from the nano- to the macroscale, and organogels. In addition, 1 is able to drive fullerene (C60) or multiwalled carbon nanotubes (MWCNTs) in an organogel by co-assembling with them.

Exploiting dimensional variability in coordination polymers: solvent promotes reversible conversion between 3D and chiral 1D architectures.

DMSO promotes dimensional variability driving the formation of Cu-bpy architectures such as a 3D nanoporous network (1) and a 1D chiral polymer (2) self-assembled from achiral building blocks. The same solvent rules a reversible conversion between 1 and 2.

Post-assembly guest oxidation in a metallo-supramolecular host and structural rearrangement to a coordination polymer.

PTA hosted in a copper metallo-supramolecular triangle undergoes post-assembly oxidation to form PTAO in aerated solutions. The oxidation is triggered by selected co-solvents that also govern the formation of the final crystalline product leading to a discrete host-guest triangle {PTAO@[Cu(o-L)]3} or to a 1D coordination polymer {(PTAO)2@[Cu8][Cu2]}∞ containing a {Cu8} ring with a double hosting pocket.

Double level selection in a constitutional dynamic library of coordination driven supramolecular polygons.

A constitutional dynamic library (CDL) of Cu(II) metallo-supramolecular polygons has been studied as a bench test to examine an interesting selection case based on molecular recognition. Sorting of the CDL polygons is achieved through a proper guest that is hosted into the triangular metallo-macrocycle constituent. Two selection mechanisms are observed, a guest induced path and a guest templated self-assembly (virtual library approach).

Self-assembly of a constitutional dynamic library of Cu(II) coordination polygons and reversible sorting by crystallization.

A small coordination constitutional dynamic library (CDL) is self-assembled from Cu(2+) ions and the ortho bis-(3-acetylacetone)benzene ligand. Two coordination polygons, a rhomboid and a triangle, establish a dynamic equilibrium. Quantitative sorting of the rhomboidal polygon is reversibly obtained by crystallization.