The first total synthesis of (R)-convolutamydine A

The first total synthesis of (R)-convolutamydine A has been achieved by the organocatalytic addition of acetone to 4,6-dibromoisatin. The absolute configuration was determined by single crystal X-ray diffraction. DFT studies were used to model the transition states for the aldol reaction and equilibrium geometries of the post-aldol reaction intermediates. The DFT study revealed that the aldol bond forming reaction was considerably endothermic.     

Collection and analytical characterisation of the atmospheric particulate in the city of Bari

In this paper an application of new procedures for atmospheric particulate analysis is illustrated. PM10, PAHs (benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), benzo[j]fluoranthene (BjF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1, 2, 3-cd]pyrene (Ip), dibenzo[a, h]anthracene (DbA)) and heavy metals (Cu, Ni, Zn, Co, Mn, Cd, Fe and Pb) were investigated. PM10 determination was performed by gravimetric method, PAHs were measured by GC-MS, and heavy metals by HPIC. An air quality monitoring campaign on the territory of Bari municipality has been organised, and its results are shown.     

Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. II: Sinks and fate

This paper reviews the transformation processes that polycyclic aromatic hydrocarbons (PAHs) undergo in the atmosphere. These processes can take place both in the gas phase and in the particulate/aerosol one. Among the gas-phase processes, the most important ones are the daytime reaction with *OH and the nighttime reaction with *NO3. The relative importance of the two processes depends on the particular PAH molecule. For instance, gaseous naphthalene is mainly removed from the atmosphere upon reaction with *OH, while gaseous phenanthrene is mainly removed by reaction with *NO3. Oxy-, hydroxy-, and nitro-PAHs are the main transformation intermediates. Reaction with ozone and photolysis play a secondary role in the transformation of gaseous PAHs. The particle-associated processes are usually slower than the gas-phase ones, thus the gas-phase PAHs usually have shorter atmospheric lifetimes than those found on particulate. Due to the higher residence time on particulate when compared with the gas phase, direct or assisted photolysis plays a relevant role in the transformation of particle-associated PAHs. Among the other processes taking place in the condensed phase, nitration plays a very important role due to the health impact of nitro-PAHs, some of them being the most powerful mutagens found so far in atmospheric particulate extracts.     

Theoretical analysis of residual dipolar coupling patterns in regular secondary structures of proteins

A new approach to the interpretation of residual dipolar couplings for the regular secondary structures of proteins is presented. This paper deals with the analysis of the steric and chiral requirements of protein secondary structures and establishes a quantitative correlation between structure periodicity and the experimental values of the backbone residual dipolar couplings. Building on the recent interpretation of the periodicity of residual dipolar couplings in alpha-helices (i.e., "dipolar waves"), a general parametric equation for fitting the residual dipolar couplings of any regular secondary structure is derived. This equation interprets the modulation of the residual dipolar couplings' periodicity in terms of the secondary structure orientation with respect to an arbitrary reference frame, laying the groundwork for using backbone residual dipolar couplings as a fast tool for determining protein folding by NMR spectroscopy.     

An improvement on geometrical parameterizations by transfinite maps

We present a method to generate a non-affine transfinite map from a given reference domain to a family of deformed domains. The map is a generalization of the Gordon–Hall transfinite interpolation approach. It is defined globally over the reference domain. Once we have computed some functions over the reference domain, the map can be generated by knowing the parametric expressions of the boundaries of the deformed domain. Being able to define a suitable map from a reference domain to a desired deformation is useful for the management of parameterized geometries.     

Ternary Sn-Ti-O Electrocatalyst Boosts the Stability and Energy Efficiency of CO2 Reduction

Simultaneously improving energy efficiency (EE) and material stability in electrochemical CO₂ conversion remains an unsolved challenge. Among a series of ternary Sn-Ti-O electrocatalysts, 3D ordered mesoporous (3DOM) Sn_0.3Ti_0.7O₂ achieves a trade-off between active-site exposure and structural stability, demonstrating up to 71.5 % half-cell EE over 200 hours, and a 94.5 % Faradaic efficiency for CO at an overpotential as low as 430 mV. DFT and X-ray absorption fine structure analyses reveal an electron density reconfiguration in the Sn-Ti-O system. A downshift of the orbital band center of Sn and a charge depletion of Ti collectively facilitate the dissociative adsorption of the desired intermediate COOH* for CO formation. It is also beneficial in maintaining a local alkaline environment to suppress H₂ and formate formation, and in stabilizing oxygen atoms to prolong durability. These findings provide a new strategy in materials design for efficient CO₂ conversion and beyond.     

Size‐Mediated Recurring Spinel Sub‐nanodomains in Li‐ and Mn‐Rich Layered Cathode Materials

Li‐ and Mn‐rich layered oxides are among the most promising cathode materials for Li‐ion batteries with high theoretical energy density. Its practical application is, however, hampered by the capacity and voltage fade after long cycling. Herein, a finite difference method for near‐edge structure (FDMNES) code was combined with in situ X‐ray absorption spectroscopy (XAS) and transmission electron microscopy/electron energy loss spectroscopy (TEM/EELS) to investigate the evolution of transition metals (TMs) in fresh and heavily cycled electrodes. Theoretical modeling reveals a recurring partially reversible LiMn₂O₄‐like sub‐nanodomain formation/dissolution process during each charge/discharge, which accumulates gradually and accounts for the Mn phase transition. From the modeling of spectra and maps of the valence state over large regions of the cathodes, it was found that the phase change is size‐dependent. After prolonged cycling, the TMs displayed different levels of inactivity.     

Bridging fluorides and hard/soft mismatch in d6 and d8 complexes: the case of [Tl(mu-F)3Ru(PPh3)3

[RuCl2(PPh3)3] reacts with thallium(I) fluoride to give either [Tl(mu-F)3Ru(PPh3)3] (1) or [Tl(mu3-F)(mu2-Cl)2Ru2(mu2-Cl)(mu2-F)(PPh3)4] (2) depending on the excess of TlF used. Both 1 and 2 were fully characterized, including X-ray structure determinations. Complex 1 reacts with dihydrogen to form the known ruthenium hydride complex [Ru(H)2(H2)(PPh3)3] upon hydrogenolysis of the Ru-F bond. The reaction of 1 with activated alkyl bromides (R-Br) gives the corresponding alkyl fluorides and the trinuclear complex [Tl(mu3-F)(mu2-F)(mu2-X)Ru2(mu2-Br)(mu2-F)(PPh3)4] (X=Br, F) (3), whose structure closely resembles that of 2. However, 1 is not active as catalyst for the nucleophilic fluorination of R-Br in the presence of thallium fluoride. The effect of the bridging coordination mode of fluoride on the Ru-F bond is discussed in terms of the HSAB principle, which suggests a more general model for predicting the stability of d6 and d8 complexes containing hard ligands (such as fluoro, oxo, and amido).     

Introduction of 4(S)-oxazolidineacetic acid, 2-oxo (D-Oxac) motif in a polypeptide chain: synthesis and conformational analysis

A four step synthesis of 4(S)-oxazolidineacetic acid, 2-oxo benzyl ester (D-Oxac-OBn) from L-Asp-OH in 45% overall yield is reported. The formation of by-products is completely avoided, by microwave irradiation and by the use of caesium carbonate as base. Moreover the synthesis and IR and 1H NMR conformational analysis of the tetramers Boc-L-Val-D-Oxac-L-Ala-OBn and Boc-L-Val-D-Oxac-Aib-L-Ala-OBn in solution is reported.     

Preliminary results and status of the MUNU experiment

We built a low background detector to measure the _ee⁻ elastic cross section at low energy. The detector has been installed close to a nuclear reactor in Bugey and it is running since almost one year. After having reduced the electron background by more than 2 orders of magnitude we are now taking data to be sensitive to a neutrino magnetic moment in the region below 10⁻¹⁰ Bohr magnetons.