Federica Sabuzi

KuQuinones as sensitizers for NiO based p-type dye-sensitized solar cells

A new series of KuQuinones (KuQs) have been synthesized and employed as dye-sensitizers for NiO-based p-type dye-sensitized solar cells (p-DSSCs). KuQs are pentacyclic quinoid compounds which are characterized by a fully conjugated structure that is responsible for the strong and broad absorption in the visible spectrum. The HOMO/LUMO states of KuQs considered here have matching energy levels with the upper edge of the NiO valence band and I−/I3− redox potential energy. These features render such compounds suitable for NiO sensitization in p-DSSCs. The new carboxylic acid-substituted KuQ derivatives proposed here differ in the length of the alkyl chain. The JV characteristic curves and the external quantum efficiency spectra have been recorded. The results showed that the performances of KuQ-sensitized cells were similar to that of the benchmark sensitizer erythrosine B (Ery B), despite the lack of electronic conjugation between the anchoring group and the light absorbing unit. This result led us to hypothesize that the photoinduced charge transfer between the excited KuQ dyes and the NiO electrode occurred through space and not via chemical bonds as it usually occurs in these systems. The mechanism of charge transfer through space has been supported by data from IR spectroscopy.

KuQuinones: a new class of quinoid compounds as photoactive species on ITO

KuQuinones constitute a new class of quinoid compounds, characterized by a broad absorption spectrum in the visible region, mainly due to their pentacyclic, highly conjugated structure, and a very low reduction potential. These properties make them promising candidates as sensitive material in photoelectrochemical devices. To this purpose, photocurrent generation measurements have been performed, in presence of an electron donor species in solution, using two different derivatives, 1-(9-hydroxynonyl)KuQuinone (KuQ(CH2)9OH) and 1-methylKuQuinone (KuQCH3), as photoactive species on indium-tin oxide surface. Electrodes have been functionalized by Langmuir–Blodgett technique, which allowed to easily prepare homogeneous mono- and multilayers of such molecules. Promising results in terms of Incident Photon to Current Efficiency values (IPCE%) and internal quantum efficiency (Φ%) have been achieved. Furthermore, the significance of the organization of the thin film obtained for the efficiency of the electron transfer process has been evidenced.

Synthesis of tetraferrocenylporphyrin and new metal complexes: Searching for reliable synthetic procedures

The tetraferrocenylporphyrin synthetic procedure was performed varying different reaction conditions. Mg, Mn, Pd and Cd complexes were synthesized and preliminarily studied. The results obtained show that the synthetic procedure strongly depends on catalyst, solvent and reagents concentration, even more than what observed with similar tetraarylporphyrins; concentration of substrates plays an important role in determining the outcome of the reactions.

Thymol and Bromothymol: Two Alleys in Biological Weapons Defeat

In recent years, mounting concerns over the use of biological weapons has raised the need to identify effective countermeasures. In the majority of cases, such weapons have been designed modifying bacterial strains to achieve antidrug-resistance. In order to reduce resistance, treatments based on essential oil extracts are available. Thus, pharmaco-resistance overcoming is possible using the compounds that plants use in preserving themselves from microorganism infections. Among all, thymol is the most interesting compound due to its high efficacy towards a wide range of pathogenic bacteria. Indeed, it shows a Minimum Inhibitory Concentration (MIC) in the micro-nanomolar range. Furthermore, its activity is related with an unspecific mechanism, as the capability in binding ion pumps and interfering with cell membrane stability. In addition, it shows negligible toxicity versus human fibroblast. Our group have been developing the synthesis of a new functionalized thymol molecule, the bromothymol. Preliminary studies have shown that bromothymol is two folds more efficient on Escherichia coli strains and at least 15-folds more active on Staphylococcus strains compared to thymol. To summarize, bromothymol showed promising results as a potential treatment against some strains, such as E. Coli O157:H7 and Yersinia, similar to that used in biological weapons.

Corroles at the real solid-liquid interface: in-situ STM investigation of a water soluble corrole layer deposited onto Au (111)

Corrole derivatives have been recently employed in many applications at the solid-liquid interface. Therefore, the structural arrangement of the molecular layers in direct contact with the liquid is of fundamental interest. We investigated in solution the deposition of molecular layers of the previously prepared water-soluble phosphorus complex of a 2-sulfonato-10-(4-sulfonatophenyl)-5,15-dimesitylcorrole [see synthesis in our previous paper, M. Naitana et al., Chem. Eur. J. 2017, 23, 905-916]. The layer formation of P corroles onto the Au(111) surface was monitored by STM in situ, that is, with the substrate immersed in the solution. Marked differences in the morphology between the organic layer formed on the substrate and that deposited after solvent evaporation (drop casting) are reported. In particular, the coating of gold was more effective and stable in the presence of liquid. Preservation of functionality of the corrole molecules after adsorption was verified. This result validates the relevance of corrole layers at the solid-liquid interface to exploit the peculiar properties of these molecules in real-world applications.

KuQuinones Equilibria Assessment for Biomedical Applications

A small library of pentacyclic quinoid compounds, called KuQuinones (KuQs), has been prepared through a one-pot reaction. KuQuinones complex structure is made up by two naphthoquinone units connected by a five-membered ring. Due to KuQs structural features, keto-enol tautomerization in solution likely occurs, leading to the generation of four different species, i.e., the enol, the enolate, the external enol and the diquinoid species. The interchange among KuQ tautomers leads to substantial spectral variations of the dye depending on the experimental conditions used. The comprehension of tautomeric equilibria of this new class of quinoid compounds is strongly required in order to explain their behavior in solution and in biological environment. UV-vis, 1H NMR spectroscopies, and DFT calculations resulted appropriate tools to understand the nature of the prevalent KuQuinone species in solution. Moreover, due to the structural similarity of KuQuinones with camptothecin (CPT), a largely used anticancer agent, KuQs have been tested against Cisplatin-resistant SKOV3 and SW480 cancer cell lines. Results highlighted that KuQs are highly active toward the analyzed cell lines and almost nontoxic for healthy cell, indicating a high specific activity.