Molecular organization of n-cyanobiphenyl liquid crystals on a molybdenite surface

The alignement and anchoring of liquid crystals on solid surfaces is a key problem for modern device technology that until now has been treated empirically, but that can now be tackled by atomistic computer simulations. Molecular dynamics (MD) simulations were used in this thesis work to study two films of 7 and 8 n-alkyl-4’cyanobiphenyl (7CB and 8CB) liquid crystals , with a thickness of 15 nm, confined between two (001) surfaces of MoS2 (molybdenite). The isotropic and nematic phases of both liquid crystals were simulated, and the resulting structures characterized structurally. A new force field was designed to model the interactions between the liquid crystal (LC) molecules and the surface of molybdenite, while an accurate force field developed previously was used to model the 7CB and 8CB molecules. The results show that the (001) molybdenite surface induces a planar orientation in both the liquid crystals. For the nematic phase of 8CB, one of the two solid/LC interfaces is composed of a first layer of molecules aligned parallel to the surface, followed by a second layer of molecules aligned perpendicular to the surface (also called, homeotropic). The effect of the surface appears to be local in nature as it is confined to the first 15 Angström of the LC film. Conversely, for the nematic phase of 7CB, a planar ordering is established into the LC film. The LC molecules at the interface with the molybdenite appear to align preferentially their alkyl chains toward the solid substrate. The resulting tilt angle of molecules was found to be in good agreement with experimental measurements available in literature. Despite the fact that the MD simulations spanned a time range of more than 100 ns, the nematic phases of both 7CB and 8CB were found not to be completely formed. In order to confirm the findings presented in this thesis, we propose to extend the current study.

Sintesi e Caratterizzazione di Elettrodi Modificati Chimicamente con nuovi complessi Carbenici del Ferro

The Chemically Modified Electrodes (CME) are widely used in electroanalytical chemistry as chemical sensors. The interest in the covalent anchoring of a redox mediator on the electrode surface is increasing, because it allows the sensibility and the selectivity of this kind of systems to improve. My work is situated in this field of research and involves the synthesis of new Iron(0) complexes that contain cyclopentadienone, N-heterocyclic carbene (NHC) and carbonyl ancillary ligands. These complexes have shown electrochemical properties similar to those of ferrocene (organometallic compound widely used as electrochemical sensor). These complexes have been properly functionalized with a EDOT group in the NHC ligand side chain that it was after used for the realization of Electrochemically Modified PEDOT thanks to copolymerization reaction between the functionalized complex and the EDOT in different amounts. All the synthetic steps were assisted by suitable characterizations (NMR, IR, ESI-MS, cyclic voltammetry and X-ray for the monomeric compound as imidazolium salt and NHC functionalized complexes; cyclic voltammetry, IR e SEM for the copolymers). The properties of the polymer as a selective sensor was preliminarily investigated for dopamine and 2-propanol.

A first survey on the status of the Posidonia oceanica meadow in Calpe Bay (Alicante, Spain).

Posidonia oceanica, endemic seagrass of the Mediterranean Sea, forms extensive meadows. It is included among the Mediterranean protected habitats by the Habitat Directive (92/43/EEC). P. oceanica meadows are exposed to anthropogenic impacts that are more evident in areas close to cities, ports or areas with a large coastal tourism development. Mean exponential decline rate of 5 % yr-1 is estimated for the Spanish meadows. If this trend is maintained, most of the meadows are predicted to halve in shoot density over the next 20 years. The meadows regression can give way to a new regime, which supposes the loss of the multiple services that the meadows provided. It is necessary to recognize situations of stress in time, before irreversible damages and changes towards alternative regimes are evident. This study has been carried out in Calpe Bay, Alicante (Spain), during May and June 2017, with the aim of assessing, for the first time, the status of the P. oceanica meadows providing a baseline data for the future monitoring scheme. The features and status of the seagrass beds have been assessed by physical, physiographical, structural and functional descriptors. The results showed that the health status classification of P. oceanica meadows in Calpe Bay vary between “equilibrium” and “disturbed”. The “disturbed” conditions were observed in a shaded area where it is probably due to the low solar radiance. In a lower limit in a shallow meadow, where it could be due to the combined effect of substrate structure and hydrodynamic regime. Finally in a touristic area where patchy impacts could be attributed to direct human disturbance (e.g. anchoring). Overall the status of P. oceanica meadows in Calpe bay is not worrying. However, it is important to develop monitoring plans to assess the dynamics of the seagrass detecting any early decline symptom in order to act, as soon as possible because, when a regression of a meadow is produced, it could not be recovered at human scales.

Direct C–H silylation and borylation of biomass derivatives by iridium heterogeneous catalysts

Furfural and its derivatives represent renewable and readily available platforms for a wide range of chemicals. Much attention has been devoted to their functionalization over the last years. TM-catalysed C–H activation has emerged as a powerful tool for synthesizing new C–C and C–X bonds. Moreover, it provides a sustainable way to obtain molecules by reducing waste and saving steps. At the same time, iridium catalysts have proven to be very active in some C–H functionalizations of several (hetero)arenes. Although very promising, this technique is still poorly applied on an industrial scale due to the severe conditions required. Continuous flow chemistry using heterogeneous catalysts appears to be a valuable way to overcome these problems. In this work, we present different solutions for the immobilization of homogeneous iridium complexes on silica gels, using bidentate amines and phosphines as anchoring ligands. We successfully employed the catalysts in C–H silylation and borylation of furfural, using C2 located directing group. In this way, we finally obtained a suitable catalyst that could be potentially applied in continuous-flow chemistry.