Mass spectrometry in the characterization of reactive metal alkoxides.

Metal alkoxides are metal-organic compounds characterized by the presence of MOC bonds (M = metal). Their chemistry seems to be, in principle, relatively simple but the number of possible reactant species arising as a consequence of their behavior is very remarkable. The physico-chemical properties of metal alkoxides are determined by many different parameters, the most important ones being the electronegativity of the metal, the ramification of the ligand, and the acidity of the corresponding alcohol. Their reactivity makes them suitable and versatile candidates for many applications, including homogeneous catalysis, synthesis of new ceramic materials through the sol-gel process and, recently, also for Cultural Heritage. Metal alkoxides are characterized by a strong tendency to give clusters and/or oligomers through oxo-bridges. Mass spectrometry has been successfully employed for the characterization of metal alkoxides in the gas-phase. Electron ionization (EI) allowed the assessment of the molecular weight and of the most relevant decomposition pathways giving information on the relative bond strength of differently substituted molecules. On the other hand, information on the reactivity in solution of these molecules have been obtained by electrospray ionization (ESI)-matrix assisted laser desorption ionization (MALDI) experiments performed on their reaction products. These data were relevant to investigate the sol-gel process. In this review, these aspects are described and the results obtained are critically evaluated. © 2016 Wiley Periodicals, Inc. Mass Spec Rev.

Re-investigation of lead(II) formate.

The crystal structure of the title compound, poly[di-µ(4)-formato-lead(II)], [Pb(HCOO)(2)](n), has been re-investigated. It consists of a three-dimensional polymeric network of Pb(2+) nodes connected by bridging formate anions. Despite having been described previously, the structural information available so far [Harrison & Steel (1982). J. Organomet. Chem. 239, 105-113] is incomplete and the reported Pnma space group is incorrect. In this work, the space-group assignment to P2(1)2(1)2(1) is discussed and a complete description of the structural features of lead(II) formate is provided.

Study of challenging calcium alkoxides in solution by electrospray ionization mass spectrometry (Part 1).

Electrosprayionization was applied on calcium altkoxides studying the mostsuitableoperativeconditions for their detection/identification. To reach this aim, calcium methoxide and ethylate were obtained by two different synthetic pathways, in order to understand their possible different aggregation states. The reaction mixture shows the presence of a supernatant and of a precipitate poorly soluble in most organic solvents. The purpose of this preliminary study is to understand the qualitative differences between the precipitated species and the ones in solution by analyzing both of them with the same analytical method. The electrospray ionization (ESI) operating conditions (voltages, temperatures, solvents) allow not only the detection of single species but also the study of clusters present in solution. Particular attention was paid to establishing the role of ESI conditions in the formation of the detected species. Experiments performed at different sprayer voltages (1 kV, 2kV, 3 kV and 4 kV) proved that ESI does not perturbate the equilibria present in the original solution, demonstrating that the technique can be a useful tool to achieve information on this class of compounds.

Study of challenging calcium alkoxides in solution by electrospray ionisation mass spectrometry (Part 2).

Calcium alkoxides in solution give rise to oligomers with different reactivity and solubility and, as observed in a previous investigation, small differences in the ligand structure lead to strong differences in the cluster composition. Electrospray ionisation mass spectrometry (ESI-MS) gives evidence of this behaviour, allowing the identification of these oligomers. In this paper, ESI was applied in the study of calcium alkoxides with different steric hindrances and with additional donor atoms on the ligands. A systematic analysis was conducted by varying the ESI instrumental parameters (voltages, temperatures) to identify the best conditions for the analysis of this class of compounds. Furthermore, particular attention was paid to the study of the best solvent to be employed, considering the possible occurrence of alcoholysis and decomplexation phenomena.

Zinc(II) complexes with dithiocarbamato derivatives: structural characterisation and biological assays on cancerous cell lines.

Zinc is one of the most important trace elements in the body and it is essential as a cofactor for the structure and function of a number of cellular molecules including enzymes, transcription factors, cellular signalling proteins and DNA repair enzymes. On the other hand, recent studies have shown that zinc could play a role both in the development of various cancers and in the induction of apoptosis in some cell types, however, no established common relationships of zinc with cancer development and progression have been identified. To date, in our research group different metal-dithiocarbamato complexes have been designed that were expected to resemble the main features of cisplatin together with higher activity, improved selectivity and bioavailability, and lower side-effects. On the basis of the obtained encouraging achievements with other metals (such as gold and copper) we have decided to enlarge the studies to the complexes of zinc(II) using the same ligands. Hereby, we report the results on the synthesis and characterisation of ZnL(2) complexes with five different dithiocarbamato derivatives, such as dimethyl-(DMDT), pyrrolidine-(PyDT), methyl-(MSDT), ethyl-(ESDT) and tert-butyl-(TSDT) sarcosinedithiocarbamate. All the obtained compounds have fully been characterised by means of several spectroscopic techniques. In addition, the crystal structure of [Zn(MSDT)(2)](2) dinuclear complex is also reported. In order to evaluate the in vitro cytotoxic properties, some biological assays have been carried out on a panel of human tumour cell lines sensible and resistant to cisplatin. Some of the tested compounds show cytotoxicity levels comparable or even greater than the reference drug (cisplatin).

Microbial deterioration of artistic tiles from the façade of the Grande Albergo Ausonia & Hungaria (Venice, Italy).

The Grande Albergo Ausonia & Hungaria (Venice Lido, Italy) has an Art Nouveau polychrome ceramic coating on its façade, which was restored in 2007. Soon after the conservation treatment, many tiles of the façade decoration showed coloured alterations putatively attributed to the presence of microbial communities. To confirm the presence of the biological deposit and the stratigraphy of the Hungaria tiles, stereomicroscope, optical and environmental scanning electron microscope observations were made. The characterisation of the microbial community was performed using a PCR-DGGE approach. This study reported the first use of a culture-independent approach to identify the total community present in biodeteriorated artistic tiles. The case study examined here reveals that the coloured alterations on the tiles were mainly due to the presence of cryptoendolithic cyanobacteria. In addition, we proved that the microflora present on the tiles was generally greatly influenced by the environment of the Hungaria hotel. We found several microorganisms related to the alkaline environment, which is in the range of the tile pH, and related to the aquatic environment, the presence of the acrylic resin Paraloid B72® used during the 2007 treatment and the pollutants of the Venice lagoon.