Daniele Vitalini

Synthesis and Characterization of Uncharged Water-Soluble Star Polymers Containing a Porphyrin Core

Uncharged water-soluble porphyrins were prepared by reaction between tetrakis(p-hydroxy-phenyl)porphyrin and chlorinated poly(ethylen glycol) methyl ethers of different molecular weights. Water-solubility was achieved by binding four poly(ethylene glycol) branches to a porphyrin core to give star polymers with molecular weights in the range 2000-21 000 Da. Structural characterization of these star polymers was performed by means of gel permeation chromatography, NMR spectroscopy, and MALDI-TOF analysis.

Effect of combined changes in delayed extraction time and potential gradient on the mass resolution and ion discrimination in the analysis of polydisperse polymers and polymer blends by delayed extraction matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Data reported here show that, in the delayed extraction matrix-assisted laser desorption/ionization time-of-flight (DE-MALDI-TOF) mass spectrometric analysis of synthetic polydisperse polymers, different experimental conditions of spectral recording are required to optimize the signal in all the m/z regions of the spectrum. The effect of combined changes in delay time and grid voltage % values on both mass resolution and mass accuracy of DE spectra of a polyethylene glycol sample (PEG(mix), with a well-defined molar distribution of its components) is discussed. The necessity of a compromise between the values of these two parameters is shown. Furthermore, the occurrence of analyte discrimination, which can invalidate the composition analysis especially in the case of polymer blends, is demonstrated. Copyright 1999 John Wiley & Sons, Ltd.

A NEW PROCEDURE FOR QUANTITATIVE CORRECTION OF MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRIC RESPONSE

A simple procedure for the correction of the decreasing detection response in a Matrix-assisted laser desorption/Ionization time-of-flight (MALDI-TOF) mass spectrum with increasing ion mass is reported. On the basis of the experimental MALDI-TOF mass spectrum of a mixture of four polymethylmethacrylate (PMMA) standards (molecular masses in the range 4–100 kDa), present in equal molar abundance, an equation describing the MALDI-TOF response has been derived. This equation has been used to correct any subsequently recorded MALDI spectrum. As an example, the procedure has been applied here to normalize the MALDI-TOF mass spectrum of a 1,20-di(bisphenoxy-A)eicosane based copolyformal (I) containing porphyrin units in the main chain. # 1998 John Wiley & Sons, Ltd.

Uncharged water-soluble porphyrin tweezers as a supramolecular sensor for α-amino acids

The binding between uncharged cobalt porphyrin tweezers and L-amino acids in aqueous solutions is studied by means of UV–vis and circular dichroism spectroscopy. By varying the length of the aliphatic bridge between the two porphyrin units, the number of cobalt ions in the porphyrin cores and the pH of the solution, the chirality induction phenomenon has been investigated. The binding of the amino acid to the porphyrin seems to occur via a coordination mechanism between the metal and the nitrogen of the amino group; the steric, hydrophobic and π–π interactions operate to stabilize the complexes. The chirogenesis displays an opposite behaviour in the presence of aromatic guests with respect to the non-aromatic ones. Moreover, the UV–vis and the induced circular dichroism spectral changes suggest that the amino acid arrangement in the tweezers is determined by many factors, so that, unlike in organic solvent, the porphyrin tweezers in aqueous solution allow for two different arrangements of the same aromatic amino acid. The experimental findings indicate that the porphyrins tweezers reported in the paper are promising in opening perspectives toward their application as a selective molecular sensor in aqueous solutions directly.

Identification of pyrolysis products of polysulphides by collisionally activated decomposition linked scanning mass spectrometry

Abstract Collisionally activated decomposition (CAD) linked scan mass spectra have been used in the identification of pyrolysis products obtained by the direct pyrolysis of some polysulphides in a mass spectrometer. Structures were determined by comparing the CAD spectra of the pyrolysis products with those of authentic compounds. The results are of help in elucidating the thermal degradation mechanisms that occur in the pyrolysis of the polysulphides investigated.

Synthesis and structural characterization by fast-atom bombardment mass spectrometry of exactly alternating copolyesters containing photolabile units in the main chain

Abstract Polycondensation between bis(2-hydroxymethylenephenyl)adipate, bis(3-hydroxypropylene)terephthalate and bis(2-hydroxyethylene)terephthalate with α-truxilloyl chloride were performed to obtain exactly alternating copolyesters containing photoreactive cyclobutane units in the main chain. The resulting copolyesters were characterized by fast-atom bombardment (f.a.b.) mass spectrometry, and the structure of the oligomers detected in the f.a.b.(+) and f.a.b.(−) mass spectra allowed confirmation of the alternating sequence present in the copolymers.

Thermal decomposition processes in alphatic-aromatic polysulphides investigated by electron impact and chemical ionization mass spectrometry

Abstract The thermal degradation of four aliphatic-aromatic polysulphides was investigated by direct pyrolysis in the ion source of a mass spectrometer operating both in electron impact and chemical ionization modes. The overall evidence indicates that the primary thermal decomposition processes of these polysulphides yield cyclic sulphides or disulphides according to a backbiting process initiated at the SH ends. A β-CH hydrogen transfer process occurring in parallel with the former produces compounds with both olefin and SH end-groups.

Copper(II) assisted self-Assembly of functionalized β-Cyclodextrins with β-Alanyl-l-histidine

Abstract A combined UV–visible, CD and ESI-MS spectroscopic approach has been followed to obtain the speciation and the bonding details of copper(II) complexes with β-cyclodextrins functionalized by means of the bio-active peptide β-alanyl- l -histidine (carnosine). A new metal-assisted self-assembled system of bifunctionalized β-cyclodextrins has been shown to exist.

Structural characterization of butadiene/acrylonitrile copolymers by fast atom bombardment mass spectrometric analysis of the partial ozonolysis products

Abstract The partial ozonolysis of three random butadiene/acrylonitrile copolymers I–III, with butadiene contents of 78, 67 and 55 mol%, respectively, has been performed in order to form low-molecular-weight products by cleavage of double bonds along the main chain. The fragments thus obtained have been directly analysed by both positive and negative fast atom bombardment mass spectrometry (f.a.b.-m.s.). According to a random distribution of butadiene (Bt) and acrylonitrile (AN) subunits in the copolymer chains, peaks due to fragments with different Bt/AN ratio in the molecule have been detected in the mass spectra. The relative abundances of the species having the same total number of AN and Bt subunits, detected in the mass spectra of ozonolysed copolymers I–III, have been compared with those calculated according to a theoretical combination of AN and Bt units. Good agreement has been found between the two sets of data. A graphical procedure for rapid determination of Bt/AN copolymer composition by f.a.b.-m.s. data has been also developed.

Freestanding photocatalytic materials based on 3D graphene and polyporphyrins

A new concept in the formulation of hybrid nanostructured materials combining high quality graphene 3D supported by Nickel foam and polyporphyrins for visible light photocatalytic application is here reported. Our innovative approach involves the development of a freestanding device able to: i) offer a high surface area to bind the photosensitizers by π-π interactions, and ii) enhance stability and photocatalytic efficiency by using cyclic porphyrin polymers. For these purposes, homo- and co-polymerization reactions by using different porphyrin (free or zinc complexed) monomers were performed. The microscopic structures and morphology of graphene polymer nanocomposites were investigated by using Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Atomic Force Microscopy (AFM). Finally, photocatalytic activity under visible light irradiation of the obtained nanocomposites was tested, by using methylene blue (MB) as organic pollutant. The obtained data suggested that hindered cyclic polymeric structures stacked on graphene surface by non-covalent interactions, restrict the formation of non photoactive aggregates and, as a consequence, induce an enhancement of photocatalytic activity. Remarkably, our systems show a degradation efficiency in the visible-light range much higher than other similar devices containing nanoporphyrin units reported in literature.