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Research paper thumbnail of Polycyclic aromatic hydrocarbons assessment in the sediments of the Porto Torres Harbor (Northern Sardinia, Italy

Marine Chemistry, 2004

The distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Porto Torres Harb... more The distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Porto Torres Harbor (north Sardinia, Italy) was investigated by gas chromatography/mass spectrometry (GCMS). PAHs concentrations in the sediment (SPAHs) ranged from 0.07 to 1.21 Ag g À 1 , indicating low to moderate PAHs pollution. Principal component analysis (PCA), the comparative evaluation of PAHs low/high molecular weight and isomeric ratios, suggests that the pollution source is petrogenic (probably due to oil spills from ship and tanker, and to petrochemical plants near the shoreline). A significant contribution from pyrolytic PAHs is found only in the most polluted sediments. Terrigenous flows (e.g., municipal or river waters) do not affect the PAHs balance of the harbor at all. The good linear correlation between chrysene concentration and the total amount of the other 15 US EPA concerning PAHs suggests the use of chrysene as a possible marker of PAHs pollution. D

Research paper thumbnail of Nature, distribution and origin of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (Northern Sardinia, Italy

Marine Pollution Bulletin, 2005

The nature, origin and distribution of US EPA polycyclic aromatic hydrocarbons (PAHs) in the sedi... more The nature, origin and distribution of US EPA polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (North Sardinia, Italy) were investigated by gas-chromatography/mass spectrometry (GCMS). PAH concentrations in the sediments ( P PAHs) ranged from 0.16 to 0.77 lg g À1 , indicating a homogeneously low level of pollution. A rather exceptional prevalence of low molecular weight PAHs was substantiated: nearly 80% of P PAHs include naphthalene (15.19%) and phenanthrene (64.47%). Carcinogenic compounds were present in very low (BaP, BkF, BaA and DBA) or negligible (BbF and Inp) concentrations. As indicated by the Phen/Ant molar ratio, the main source of PAHs is petrogenic, probably due to oil spills from shipping. The low/high molecular weight ratio (ranging between 1.2 and 26) distinguishes the sediments of the tourist harbor from those of the commercial/ industrial harbor. Moreover, a slight but meaningful pyrolytic contribution to pollution was found in the tourist harbor, which has the most polluted sediments in the whole harbor. Finally, good linear correlations were found between a selected PAH (Phen and Naph) and selected sums of PAHs (i.e. the total amount of the other 15 US EPA and the sum of low molecular weight PAHs).

Research paper thumbnail of Electrochemical and spectroelectrochemical characterisation of poly(3′-hydroxymethyl-2,2′:5′,2″-terthiophene

Synthetic Metals, 2006

Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electroch... more Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The investigated compounds are 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrins (Ph) 2 (P(O)-(OEt) 2 ) 2 PorM and 5,15-bis(diethoxyphosphoryl)-10,20-di(para-carbomethoxyphenyl)porphyrins (PhCOOMe) 2 (P(O)(OEt) 2 ) 2 PorM where M = 2H, Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Pd(II). The free-base and five metalated porphyrins with nonredox active centers undergo two ring-centered oxidations and two ring-centered reductions, the latter of which is followed by a chemical reaction of the porphyrin dianion to give an anionic phlorin product. The phlorin anion is electroactive and can be reoxidized by two electrons to give back the starting porphyrin, or it can be reversibly reduced by one electron at more negative potentials to give a phlorin dianion. The chemical conversion of the porphyrin dianion to a phlorin anion proceeds at a rate that varies with the nature of the central metal ion and the solvent. This rate is slowest in the basic solvent pyridine as compared to CH 2 Cl 2 and PhCN, giving further evidence for the involvement of protons in the chemical reaction leading to phlorin formation. Calculations of the electronic structure were performed on the Ni(II) porphyrin dianion, and the most favorable atoms for electrophilic attack were determined to be the two phosphorylated carbon atoms. Phlorin formation was not observed after the two-electron reduction of the cobalt porphyrins due to the different oxidation state assignment of the doubly reduced species, a Co(I) π anion radical in one case and an M(II) dianion for all of the other derivatives. Each redox reaction was monitored by thin-layer UV−visible spectroelectrochemistry, and an overall mechanism for each electron transfer is proposed on the basis of these data.

Research paper thumbnail of Synthesis and electrochemical polymerisation of 3′-functionalised terthiophenes

Electrochimica Acta, 2006

A new terthienyl derivative, 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine, was ... more A new terthienyl derivative, 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine, was synthesised in order to electrogenerate a new conducting polymer as an electrode coating suitable to complex metal ions. The characteristics of the system obtained have been defined through electrochemical and spectroelectrochemical techniques. The physical and chemical properties of 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine are compared with those of 3 -hydroxymethyl-2,2 :5 ,2 -terthiophene, i.e. the corresponding trimer not bearing the terpyridine ligand. Under the same conditions for both monomers, both electrochemical and spectroelectrochemical tests show that 4 -[(2,2 :5 ,2 -terthien-3yl)methoxy]-2,2 :6 ,2 -terpyridine leads to the formation of a narrower molecular weight distribution, with shorter-conjugated polymer chains.

Research paper thumbnail of Electrochemical behaviour of cyclometallated gold(III) complexes. Evidence of transcyclometallation in the fate of electroreduced species

Journal of Organometallic Chemistry, 2001

The electrochemical behaviour of a series of neutral and cationic N -C and N-N-C cyclometallated ... more The electrochemical behaviour of a series of neutral and cationic N -C and N-N-C cyclometallated gold(III) species: ([Au(py 1 )(Cl) 2 ], Hpy 1 =2-benzylpyridine; [Au(bipy n )(Cl)][PF 6 ], Hbipy 1 = 6-benzyl-2,2%-bipyridine, Hbipy 2 = 6-(1-methylbenzyl)-2,2%-bipyridine, Hbipy 3 =6-(1,1-dimethylbenzyl)-2,2%-bipyridine, Hbipy 4 = 6-phenyl-2,2%-bipyridine) has been investigated in different solvent systems using cyclic voltammetry and controlled-potential coulometry. All the species considered show, in cyclic voltammetry, an irreversible one-electron reduction in the potential range − 0.9/−1.2 V versus Fc +/0 , using a Pt electrode. On the other hand, exhaustive coulometries have shown the consumption of a number of Faraday per mole within the range 1-2. The very complex decomposition of the electrogenerated species affords elemental gold and significant amounts of different gold by-products. In some situations (e.g. reduction of [Au(bipy 4 )(Cl)][PF 6 ]), working with 0.1 mol dm − 3 Na[PF 6 ], CH 3 CN solvent system, it has been possible to characterise the most abundant gold(III) compound, by NMR, FAB-MS, and elemental analysis. The analytical and spectroscopic data provide evidence for the N -C bis-cyclometallated gold(III) derivative (e.g.

Research paper thumbnail of Platinum complexes with NNC ligands. Syntheses, electrochemical and spectroscopic characterisations of platinum(II) and relevant electroreduced species

Inorganica Chimica Acta, 2000

A series of cyclometallated platinum(II) species with N N C ligands (N N C= ortho-C-deprotonated ... more A series of cyclometallated platinum(II) species with N N C ligands (N N C= ortho-C-deprotonated form of 6-benzyl-substituted 2,2%-bipyridines) and different fourth monodentate ligands (Cl − , I − , CN − , CO, PPh 3 , Py, MeCN) has been investigated electrochemically, with particular emphasis to the analysis of the relatively stable one-electron reduced species. EPR spectra have been recorded at different temperatures on the electroreduced solutions. The analyses were supported by a systematic comparison with simulated spectra and allowed a definition of the interaction of the additional unpaired electron with the 195 Pt, 14 N, and 1 H nuclei present in the molecule. Attention has been also paid to the effects of the ligands on the thermodynamics (E 1/2,r ) of the reduction, as well as to some reactivity aspects of the substrates that could be shown by voltammetric tests. A number of these compounds have been synthesised for the first time, so that a full characterisation has been performed.

Research paper thumbnail of Polycyclic aromatic hydrocarbons assessment in the sediments of the Porto Torres Harbor (Northern Sardinia, Italy

Marine Chemistry, 2004

The distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Porto Torres Harb... more The distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Porto Torres Harbor (north Sardinia, Italy) was investigated by gas chromatography/mass spectrometry (GCMS). PAHs concentrations in the sediment (SPAHs) ranged from 0.07 to 1.21 Ag g À 1 , indicating low to moderate PAHs pollution. Principal component analysis (PCA), the comparative evaluation of PAHs low/high molecular weight and isomeric ratios, suggests that the pollution source is petrogenic (probably due to oil spills from ship and tanker, and to petrochemical plants near the shoreline). A significant contribution from pyrolytic PAHs is found only in the most polluted sediments. Terrigenous flows (e.g., municipal or river waters) do not affect the PAHs balance of the harbor at all. The good linear correlation between chrysene concentration and the total amount of the other 15 US EPA concerning PAHs suggests the use of chrysene as a possible marker of PAHs pollution. D

Research paper thumbnail of Nature, distribution and origin of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (Northern Sardinia, Italy

Marine Pollution Bulletin, 2005

The nature, origin and distribution of US EPA polycyclic aromatic hydrocarbons (PAHs) in the sedi... more The nature, origin and distribution of US EPA polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (North Sardinia, Italy) were investigated by gas-chromatography/mass spectrometry (GCMS). PAH concentrations in the sediments ( P PAHs) ranged from 0.16 to 0.77 lg g À1 , indicating a homogeneously low level of pollution. A rather exceptional prevalence of low molecular weight PAHs was substantiated: nearly 80% of P PAHs include naphthalene (15.19%) and phenanthrene (64.47%). Carcinogenic compounds were present in very low (BaP, BkF, BaA and DBA) or negligible (BbF and Inp) concentrations. As indicated by the Phen/Ant molar ratio, the main source of PAHs is petrogenic, probably due to oil spills from shipping. The low/high molecular weight ratio (ranging between 1.2 and 26) distinguishes the sediments of the tourist harbor from those of the commercial/ industrial harbor. Moreover, a slight but meaningful pyrolytic contribution to pollution was found in the tourist harbor, which has the most polluted sediments in the whole harbor. Finally, good linear correlations were found between a selected PAH (Phen and Naph) and selected sums of PAHs (i.e. the total amount of the other 15 US EPA and the sum of low molecular weight PAHs).

Research paper thumbnail of Electrochemical and spectroelectrochemical characterisation of poly(3′-hydroxymethyl-2,2′:5′,2″-terthiophene

Synthetic Metals, 2006

Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electroch... more Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The investigated compounds are 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrins (Ph) 2 (P(O)-(OEt) 2 ) 2 PorM and 5,15-bis(diethoxyphosphoryl)-10,20-di(para-carbomethoxyphenyl)porphyrins (PhCOOMe) 2 (P(O)(OEt) 2 ) 2 PorM where M = 2H, Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Pd(II). The free-base and five metalated porphyrins with nonredox active centers undergo two ring-centered oxidations and two ring-centered reductions, the latter of which is followed by a chemical reaction of the porphyrin dianion to give an anionic phlorin product. The phlorin anion is electroactive and can be reoxidized by two electrons to give back the starting porphyrin, or it can be reversibly reduced by one electron at more negative potentials to give a phlorin dianion. The chemical conversion of the porphyrin dianion to a phlorin anion proceeds at a rate that varies with the nature of the central metal ion and the solvent. This rate is slowest in the basic solvent pyridine as compared to CH 2 Cl 2 and PhCN, giving further evidence for the involvement of protons in the chemical reaction leading to phlorin formation. Calculations of the electronic structure were performed on the Ni(II) porphyrin dianion, and the most favorable atoms for electrophilic attack were determined to be the two phosphorylated carbon atoms. Phlorin formation was not observed after the two-electron reduction of the cobalt porphyrins due to the different oxidation state assignment of the doubly reduced species, a Co(I) π anion radical in one case and an M(II) dianion for all of the other derivatives. Each redox reaction was monitored by thin-layer UV−visible spectroelectrochemistry, and an overall mechanism for each electron transfer is proposed on the basis of these data.

Research paper thumbnail of Synthesis and electrochemical polymerisation of 3′-functionalised terthiophenes

Electrochimica Acta, 2006

A new terthienyl derivative, 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine, was ... more A new terthienyl derivative, 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine, was synthesised in order to electrogenerate a new conducting polymer as an electrode coating suitable to complex metal ions. The characteristics of the system obtained have been defined through electrochemical and spectroelectrochemical techniques. The physical and chemical properties of 4 -[(2,2 :5 ,2 -terthien-3 -yl)methoxy]-2,2 :6 ,2 -terpyridine are compared with those of 3 -hydroxymethyl-2,2 :5 ,2 -terthiophene, i.e. the corresponding trimer not bearing the terpyridine ligand. Under the same conditions for both monomers, both electrochemical and spectroelectrochemical tests show that 4 -[(2,2 :5 ,2 -terthien-3yl)methoxy]-2,2 :6 ,2 -terpyridine leads to the formation of a narrower molecular weight distribution, with shorter-conjugated polymer chains.

Research paper thumbnail of Electrochemical behaviour of cyclometallated gold(III) complexes. Evidence of transcyclometallation in the fate of electroreduced species

Journal of Organometallic Chemistry, 2001

The electrochemical behaviour of a series of neutral and cationic N -C and N-N-C cyclometallated ... more The electrochemical behaviour of a series of neutral and cationic N -C and N-N-C cyclometallated gold(III) species: ([Au(py 1 )(Cl) 2 ], Hpy 1 =2-benzylpyridine; [Au(bipy n )(Cl)][PF 6 ], Hbipy 1 = 6-benzyl-2,2%-bipyridine, Hbipy 2 = 6-(1-methylbenzyl)-2,2%-bipyridine, Hbipy 3 =6-(1,1-dimethylbenzyl)-2,2%-bipyridine, Hbipy 4 = 6-phenyl-2,2%-bipyridine) has been investigated in different solvent systems using cyclic voltammetry and controlled-potential coulometry. All the species considered show, in cyclic voltammetry, an irreversible one-electron reduction in the potential range − 0.9/−1.2 V versus Fc +/0 , using a Pt electrode. On the other hand, exhaustive coulometries have shown the consumption of a number of Faraday per mole within the range 1-2. The very complex decomposition of the electrogenerated species affords elemental gold and significant amounts of different gold by-products. In some situations (e.g. reduction of [Au(bipy 4 )(Cl)][PF 6 ]), working with 0.1 mol dm − 3 Na[PF 6 ], CH 3 CN solvent system, it has been possible to characterise the most abundant gold(III) compound, by NMR, FAB-MS, and elemental analysis. The analytical and spectroscopic data provide evidence for the N -C bis-cyclometallated gold(III) derivative (e.g.

Research paper thumbnail of Platinum complexes with NNC ligands. Syntheses, electrochemical and spectroscopic characterisations of platinum(II) and relevant electroreduced species

Inorganica Chimica Acta, 2000

A series of cyclometallated platinum(II) species with N N C ligands (N N C= ortho-C-deprotonated ... more A series of cyclometallated platinum(II) species with N N C ligands (N N C= ortho-C-deprotonated form of 6-benzyl-substituted 2,2%-bipyridines) and different fourth monodentate ligands (Cl − , I − , CN − , CO, PPh 3 , Py, MeCN) has been investigated electrochemically, with particular emphasis to the analysis of the relatively stable one-electron reduced species. EPR spectra have been recorded at different temperatures on the electroreduced solutions. The analyses were supported by a systematic comparison with simulated spectra and allowed a definition of the interaction of the additional unpaired electron with the 195 Pt, 14 N, and 1 H nuclei present in the molecule. Attention has been also paid to the effects of the ligands on the thermodynamics (E 1/2,r ) of the reduction, as well as to some reactivity aspects of the substrates that could be shown by voltammetric tests. A number of these compounds have been synthesised for the first time, so that a full characterisation has been performed.