From Small Metal Clusters to Molecular Nanoarchitectures with a Core-Shell Structure: The Synthesis, Redox Fingerprint, Theoretical Analysis, and Solid-State Structure of [Co38As12(CO)50]4.

The cluster [Co38As12(CO)50]4- was obtained by pyrolysis of [Co6As(CO)16]-. The metal cage features a closed-packed core inside a Co/As shell that progressively deforms from a cubic face-centered symmetry. The redox and acid-base reactivities were determined by cyclic voltammetry and spectrophotometric titrations. The calculated electron density revealed the shell-constrained distribution of the atomic charges, induced by the presence of arsenic.

Evaluation of chitosan aggregates as pickering emulsifier for the remediation of marine sediments.

To restore the marine environments contaminated by oil spills to an acceptable state, sediments are commonly washed with seawater, and surfactants added into the aqueous solution to increase the oil recovery. However, the resulting mixture may release toxic break-down products, and the surfactants may themselves pose an environmental risk to marine species. In this work we investigated for the first time the addition of chitosan nanoparticles to the washing solution as an alternative and greener method to ensure the cleanup of contaminated sediments. Results showed 65.1 ± 6.4% of average removal from sand and seafloor sediments artificially contaminated at 4 wt % with crude oils displaying different specific gravity. These results were comparable to those obtained with commercial surfactant mixtures containing non-ionic and anionic surfactant (67.8 ± 5.2% removal). Moreover it was possible to recover the crude oil from the washing solution thanks to the reversible demulsification induced by the addition of CO2.

Multi-analytical characterization of perigonadal fat in bluefin tuna: from waste to marine lipid source.

BACKGROUND: Marine lipids are widely recognized as supplements beneficial to health in the human diet. Bluefin tuna, as most migrating fish, may have high and variable marine lipid contents in their tissues. The viscera of the specimens caught in the Mediterranean Sea are generally discarded. Only ovaries are (locally) used for artisanal seafood preparations. RESULTS: A multi-analytical approach carried out using infrared (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS) revealed that the perigonadal fats usually discarded during bluefin tuna evisceration are characterized by a high relative abundance of polyunsaturated triacylglycerols (76.2% of dry mass), with docosahexaenoic (DHA, 22:6) and eicosapentaenoic (EPA, 20:5) acids preferentially located at the sn-2 position of the glycerol backbone. By contrast, in fats from the ovarian tissues, no wax esters and phospholipids were evidenced. Cholesterol was found in very low amounts (84 mg/100 g ovarian tissue). In vitro assays showed that this fatty material is rapidly hydrolyzed by lipase and is prone to auto-oxidation, especially if compared to the stable wax esters contained in the ovary. CONCLUSION: The results show that the perigonadal fats of bluefin tuna, traditionally wasted after evisceration, may be an interesting source for the preparation of marine lipid supplements that do not require complex fractionation processes. © 2019 Society of Chemical Industry.

Lipid classes and fatty acids composition of the roe of wild Silurus glanis from subalpine freshwater.

The fat content and the fatty acid composition of the roe of European catfish (Silurus glanis) wild specimens captured in the Lambro river basin (Como, Northern Italy) were investigated in order to assess their nutritional value. Total extracted lipid values on roe weight were 5.8-6.3%. Phospholipids (40.2-43.6%) and triacylglycerols (31.8-34.7%) were the most represented lipid classes. Relevant amount of cholesteryl esters (14.3-15.6%) were also detected. The main fatty acids were palmitic, oleic and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA). Total saturated fatty acids were 28.1-30.9%, monounsaturated fatty acids were 28.2-30.6%, and polyunsaturated fatty acids (PUFAs) were 26.7-29.1%. The good found content of phospholipids and ω3-polyunsaturated fatty acids encourage further investigation for the exploitation of Silurus glanis roe in food products and/or supplements.

Sphingoid esters from the molecular distillation of squid oil: A preliminary bioactivity determination.

A mixture of sphingoid esters was isolated (1.4% w/w) from the molecular distillation of crude squid visceral oil. A preliminary investigation on the bioactivity profile and toxic potential of this residue was carried out by in vitro experiments. No cytotoxicity and a moderate lipase inhibition activity were highlighted.

Platinum carbonyl clusters stabilized by Sn(II)-based fragments: syntheses and structures of [Pt6(CO)6(SnCl2)2(SnCl3)4](4-), [Pt9(CO)8(SnCl2)3(SnCl3)2(Cl2SnOCOSnCl2)](4-) and [Pt10(CO)14{Cl2Sn(OH)SnCl2}2](2.).

The reaction of [Pt15(CO)30](2-) with increasing amounts of SnCl2 affords [Pt8(CO)10(SnCl2)4](2-) (2), [Pt10(CO)14{Cl2Sn(OH)SnCl2}2](2-) (5), [Pt6(CO)6(SnCl2)2(SnCl3)4](4-) (3), [Pt9(CO)8(SnCl2)3(SnCl3)2(Cl2SnOCOSnCl2)](4-) (4) and [Pt5(CO)5{Cl2Sn(OR)SnCl2}3](3-) (R = H, Me, Et, and (i)Pr) (1-R). 1-R and 2 have been previously described, whereas 3-5 are herein reported for the first time. The species 1-3 are the main products of the reaction under different experimental conditions, whereas 4 and 5 are by-products of the synthesis of 3 and 2, respectively. From a structural point of view, the clusters 1-5 all show a perfect segregation of the two metals, which are composed of a low valent Pt core decorated on the surface by Sn(II) fragments such as SnCl2, [SnCl3](-), [Cl2Sn(OH)SnCl2](-) and [Cl2SnOCOSnCl2](2-). These fragments behave as two electron donor ligands via each Sn-atom (and also the C-atom in the case of [Cl2SnOCOSnCl2](2-)). The [Cl2SnOCOSnCl2](2-) ligand is rather unique and may be viewed as a bis-stannyl-carboxylate, a carbon dioxide µ3:k(3)-C,O,O'-CO2 or a carbonite ion [CO2](2-) stabilized by coordination to metal atoms. Compounds 1-5 have been fully characterised via IR spectroscopy, X-ray crystallography and DFT calculations.

Cooperative effects of electron donors and acceptors for the stabilization of elusive metal cluster frameworks: synthesis and solid-state structures of [Pt19(CO)24(µ4-AuPPh3)3]- and [Pt19(CO)24{µ4-Au2(PPh3)2}2].

The anionic cluster [Pt(19)(CO)(22)](4-) (1), of pentagonal symmetry, reacts with CO and AuPPh(3)(+) fragments. Upon increasing the Au:Pt(19) molar ratio, different species are sequentially formed, but only the last two members of the series could be characterized by X-ray diffraction, namely, [Pt(19)(CO)(24)(µ(4)-AuPPh(3))(3)](-) (2) and [Pt(19)(CO)(24){µ(4)-Au(2)(PPh(3))(2)}(2)] (3). The metallic framework of the starting cluster is completely modified after the addition of CO and AuL(+), and both products display the same platinum core of trigonal symmetry, with closely packed metal atoms. The three AuL(+) units cap three different square faces in 2, whereas four AuL(+) fragments are grouped in two independent bimetallic units in the neutral cluster 3. Electrochemical and spectroelectrochemical studies on 2 showed that its redox ability is comparable with that of the homometallic 1.

Structural variations, electrochemical properties and computational studies on monomeric and dimeric Fe-Cu carbide clusters, forming copper-based staple arrays.

The halide ligands of [Fe(4)C(CO)(12)(CuCl)(2)](2-) (1) and [Fe(5)C(CO)(14)CuCl](2-) (2) can be displaced by N-, P- or S-donors. Beside substitution, the clusters easily undergo structural rearrangements, with loss/gain of metal atoms, and formation of Fe(4)Cu/Fe(4)Cu(3) metallic frameworks. Thus, the reaction of 1 with excess dppe yielded [{Fe(4)C(CO)(12)Cu}(2)(µ-dppe)](2-) (3). [{Fe(4)C(CO)(12)Cu}(2)(µ-pyz)](2-) (4) was obtained by reaction of 2 with Ag(+) and pyrazine. [Fe(4)C(CO)(12)Cu-py](-) (5) was formed more directly from [Fe(4)C(CO)(12)](2-), [Cu(NCMe)(4)](+) and pyridine. [Fe(4)Cu(3)C(CO)(12)(µ-S(2)CNEt(2))(2)](-) (6) and [{Fe(4)Cu(3)C(CO)(12)(µ-pz)(2)}(2)](2-) (7) were prepared by substitution of the halides of 1 with diethyldithiocarbamate and pyrazolate, in the presence of Cu(i) ions. All of these products were characterized by X-ray analysis. 3 and 4 and 5 are square based pyramids, with iron in the apical sites, the bridging ligands connect the two copper atoms in 3 and 4. 6 and 7 are octahedral clusters with an additional copper ion held in place by the two bridging anionic ligands, forming a Cu(3) triangle with Cu-Cu distances ranging 2.63-3.13 Å. In 7, an additional unbridged cuprophilic interaction (2.75 Å) is formed between two such cluster units. DFT calculations were able to reproduce the structural deformations of 3-5, and related their differences to the back-donation from the ligand to Cu. Additionally, DFT found that, in solution, the tight ion pair [NEt(4)](2)7 is almost isoenergetic with the monomeric form. Thus, 3, 4 and 7 are entities of nanometric size, assembled either through conventional metal-ligand bonds or weaker electrostatic interactions. None of them allows electronic communication between the two monomeric units, as shown by electrochemistry and spectroelectrochemical studies. (dppe = PPh(2)CH(2)CH(2)PPh(2), pyz = pyrazine C(4)N(2)H(4), py = pyridine C(5)H(5)N, pz = pyrazolate C(3)N(2)H(3)(-)).

FT-IR spectroscopy and DFT calculations on fluorinated macromer diols: IR intensity and association properties.

Fluorinated macromeric diols have been investigated by means of Fourier transform infrared (FT-IR) spectroscopy; the absolute intensities of characteristic bands of OH stretching have been determined and related to aggregation phenomena. Main results show that the ratio between "free" and "hydrogen-bonded" OH groups strictly depends on the polarity of chemical environment (macromeric-polymeric matrix). The intepretation of the experimental data has been supported by density functional theory (DFT) calculations on suitable molecular models, validating the results obtained both qualitatively and quantitatively.

Copolymerization of Fe4Cu2C(CO)12 moieties with bidentate N-ligands: synthesis and crystal structure of the [Fe4Cu2(micro6-C)(CO)12(micro-bipy)]4.8THF square tetramer and the infinite [Fe4Cu2(micro6-C)(CO)12(micro-L-L)]infinity zigzag chains.

Substitution of the acetonitrile ligands in Fe(4)Cu(2)C(CO)(12)(MeCN)(2) with bidentate L-L ligands, such as 4,4'-bipyridine (bipy), pyrazine (pyz) or p-dicyanobenzene (p-DCB), gives rise to either infinite [Fe(4)Cu(2)(micro(6)-C)(CO)(12)(micro-L-L)](infinity) zigzag chain polymers or to [Fe(4)Cu(2)(micro(6)-C)(CO)(12)(micro-L-L)](4).8THF square oligomers, as a function of the crystallization solvent.

A traditional synthetic method, and a new structural motif, for molybdenum-gold clusters: synthesis and solid-state structure of Au8{Mo(CO)5}4(PPh3)4.

The neutral cluster [Au8Mo4(CO)20(PPh3)4] was synthesized in low yield from [AuCl(PPh3)] and [Mo2(CO)10]2- in acetonitrile at room temperature. The cluster was characterized by X-ray analysis, IR, and 31P NMR spectroscopy. Its solid-state structure consists of four Au(3)Mo tetrahedral units, fused by four Au atoms in a ring. The average bond lengths are Au-Au 2.77 Angstrom and Mo-Au 2.93 Angstrom. The internal angles of the planar square ring are very close to 90 degrees.

Electron transfer and CO addition to polynitrido cobalt carbonyl clusters: parallel pathways for conversion of the [Co10N2(CO)19]4- anion to the novel [Co11N2(CO)21]3- anion.

The redox aptitude of the dinitrido anion [Co10N2(CO)19]4- has been tested from both chemical and electrochemical points of view, together with its reactivity toward CO that induces disproportionation. In any case, through a remarkable overlapping of intermediate steps, the new anion [Co11N2(CO)21]3- (4) is eventually obtained. A detailed study of the pathways to 4 allowed the identification of three labile intermediates by their characteristic IR spectra as well as their electrochemical and paramagnetic properties. The unprecedented structure of trianion 4 has been studied in details in two different crystalline salts.

Iron-Rhodium and Iron-Iridium Mixed-Metal Nitrido-Carbonyl Clusters. Synthesis, Characterization, Redox Properties, and Solid-State Structure of the Octahedral Clusters [Fe(5)RhN(CO)(15)](2)(-), [Fe(5)IrN(CO)(15)](2)(-), and [Fe(4)Rh(2)N(CO)(15)](-). Infrared and Nuclear Magnetic Resonance Spectroscopic Studies on the Interstitial Nitride.

The cluster [Fe(5)RhN(CO)(15)](2)(-) was synthesized in 40% yield from [Fe(4)N(CO)(12)](-) and [Rh(CO)(4)](-) in refluxing tetrahydrofuran, whereas the analogous anion [Fe(5)IrN(CO)(15)](2)(-) was prepared in CH(3)CN at room temperature from [Fe(6)N(CO)(15)](3)(-) and [Ir(C(8)H(14))(2)Cl](2); the yields are higher than 60%. The monoanion [Fe(4)Rh(2)N(CO)(15)](-) was obtained in 70% yield from [Fe(5)RhN(CO)(15)](2)(-) and hydrated RhCl(3). The solid-state structures of the three anions were determined on their [PPh(4)](+) salts: the six metal atoms are arranged in octahedral cages and are coordinated to 3 edge-bridging and 12 terminal carbonyl ligands and to a &mgr;(6)-N ligand. The Rh and Ir atoms have less terminal COs than Fe, in order to equalize the excess electrons at the d(9) metal centers. The two rhodium atoms in [Fe(4)Rh(2)N(CO)(15)](-) are directly bound. The (15)N NMR spectra of the three compounds have been recorded; the signals of the nitride ligands were found at delta = 514 ppm for the dianions and 470 ppm for [Fe(4)Rh(2)N(CO)(15)](-); any group 9 atom shifts the resonance of nitrogen to higher fields. The coupling constants J((15)N-(103)Rh) are 8-9 Hz. The vibrational patterns of the metal cores have been interpreted on the basis of an idealized M(6) octahedral arrangement, subsequently modified by the perturbations given by different atomic masses and M-M stretching force constants. The motions of the nitrogen are related to the idealized symmetry of the cage; the M-N force constant values depend on the type of metal and on the charge of the anion. The dianions [Fe(5)MN(CO)(15)](2)(-) can be electrochemically oxidized at -20 degrees C to their short-lived monoanions, which can be characterized by EPR spectroscopy. In contrast, the cluster [Fe(4)Rh(2)N(CO)(15)](-) undergoes a single-step 2-electron reduction to the partially stable trianion [Fe(4)Rh(2)N(CO)(15)](3)(-), which was also characterized by EPR spectroscopy. The Fe-Rh nitride clusters are active catalysts for the hydroformylation of 1-pentene, but display low selectivity (35-65%) in n-hexanal and are demolished under catalytic conditions.