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This study represents the first attempt to combine mid infrared (MIR) spectroscopy and multivariate data processing for prediction of alcohol degree, sugars content and total acidity in straw wine. 302 Italian samples, representing different vintages, production regions and grape varieties, were analysed using FT-MIR spectroscopy and reference methods. New regression functions based on a combination of Orthogonal Signal Correction and Partial Least Squares regression are proposed for prediction of quality parameters: this approach allows overcoming the issue of matrix complexity, reducing spectral interferences and enhancing the information embodied in fingerprinting data. The models proposed are characterised by an excellent reliability, with low error in prediction (alcohol: 0.28%; sugars: 9.9 g/L; acidity: 0.29 g/L) comparable both to reference methods and table wine models. Results demonstrate that vibrational spectroscopy, combined with a proper multivariate data strategy, represents a suitable strategy for the quick and non-destructive assessment of quality parameters of straw wine.

Background and Aims Commercial enzyme preparations used in winemaking are mixtures of several enzymatic activities, such as pectinases, cellulases and hemicellulases. The aim of this work was to evaluate the side activities of commercial enzyme preparations and their collateral effects on white wine. Methods and Results The β-glucosidase, cinnamoyl esterase and protease activities of 15 enzyme preparations currently available in the market were screened. Must was treated with the enzyme preparations, and the collateral effects on white wine were evaluated. The application of cinnamoyl esterase-rich preparations induced an increase in hydroxycinnamic acids and 4-vinylguaiacol in the wine that reached a final concentration about twice that of the no enzyme control. Cinnamoyl esterase activity, above 50 U/g or mL of preparation on chlorogenic acid, leads to the risk of an increase of the volatile phenols during fermentation. Enzyme addition to the must influenced the aromatic composition of wine in terms of alcohol, volatile acids and esters. Enzyme treatment led to a decrease in protein concentration and a reduction of haze but was ineffective in resolving protein instability. Conclusions Enzyme preparations formulated for aroma release are more prone to induce collateral effects during winemaking. Significance of the Study Our study clearly highlights that enzyme treatment of must may significantly affect the volatile composition of wine. This result can assist the choice of the most suitable enzyme treatment to improve wine composition.

The reaction of RhCl3 · 3H2O with SbPh3 (Ph, C6H5) in ethanol produced mer-[RhCl3(SbPh3)3] (1), as the main product, together with trans-[RhCl2(Ph)(SbPh3)3] (2) (R. Cini, G. Giorgi, L. Pasquini, Inorg. Chim. Acta 196 (1992) 7; A. Cavaglioni, R. Cini, J. Chem. Soc., Dalton Trans. (1997) 1149). Ways to improve the yield for 1 and 2 were a subject of further works by this laboratory during the past decade and the reactivity of the organometallic compound 2 was investigated towards a variety of bases. Long sought single crystals of 1 suitable for X-ray diffraction have been obtained from hot acetone solution. The metal centre has a pseudo-octahedral coordination environment with the three chloride anions and the three SbPh3 molecules in mer positions. The Rh–Cl bond trans to Sb is significantly weakened by the high trans influence by antimony itself. This gives the rationale for the formation of 2 from RhCl3 and SbPh3 via the preliminary formation of 1, followed by dissociation of the activated chloride anion, and the subsequent formation of the Rh–C(Ph) linkage. The reaction of 1 with 2-thio-1,3-pyrimidine (Htpym) in ethanol produces crystalline [Rh( N 1, S 2-tpym)2( N 1(Sb), S 2(Rh)-tpym)(SbPh3)] (3). Single crystals suitable for X-ray diffraction studies as obtained from ethanol/diethyl-ether contain a complex molecule and a quarter of an ethanol molecule in the asymmetric unit. Two out of three tpym− anions chelate the metal centre via the N1 and S2 atoms, whereas the third tpym− anion behaves as mono-dentate through the S2 atom only. The sixth co-ordination position is occupied by the Sb atom. Interestingly, one of the N atoms of the monodentate tpym− anion behaves as electron donor to Sb and a Sb–N linkage forms (d(Sb–N), 2.846 A). As a consequence, an unusual totally hetero-atomic five-membered co-ordination ring of the type RhSCNSb(Rh) forms. A molecular modelling analysis at the hybrid density functional level DFT-B3LYP was performed on selected co-ordination molecules.

The reaction of [RhCl2(Ph)(PPh3)2] with purine-6-thione (H2tp) in alcohol produced the title compound which consists of aggregates of [Rh(C6H5)(H1,H9-H2tp)2(PPh3)]2+ and [Rh(C6H5)(H1,H9-H2tp)(H9-Ht...

The mononuclear compounds trans-dichloro(η1-phenyl)cis-bis(pyrazine)(triphenylstibine) rhodium(III) (1), and trans-dichloro(η1-rmphenyl) N-(2-cyanoethylpyrole)trans-bis(triphenylstibine)rhodium (III) (3) were prepared from trans-dichloro(η1-phenyl)tris(triphenylstibine)rhodium(III) in ethanol. The mononuclear compounds trans-dichloro(η1-phenyl)trans-bis(pyridine)(thiazole)rhodium(III) (2) and trans-dichloro(η1-phenyl)trans-bis(pyridine)(pyrazine)rhodium(III) (4) were obtained from trans-dichloro(η1-phenyl)tris(pyridine)rhodium(III) in methanol. Compounds1 and2 were analysedvia X-ray diffraction techniques from single crystals. The four compounds were characterized by spectroscopy and elemental analysis. The coordination sphere geometry for all the complexes is octahedral; thetrans influence exerted by the phenyl ligand is responsible for a long Rh N bond distance (2.263(3)A) and of large downfield shifts for1H NMR signals. The pyrazine ligands are monodentate in both1 and4. In the solid state the pyrazine ligands do not bridge the metal centres. Compounds1 and2 are barely stable in solution at room temperature. The thiazole molecule of2 bonds the metal through the nitrogen atom whereas sulfur does not show any donating ability. An extended-Huckel analysis shows that the pyrazine ligands contribute significantly to the frontier unoccupied molecular orbitals. The atomic charges on the non-metal bound nitrogen atoms of pyrazine ligands is −0.175 e in agreement with a bridging ability between two metal centres for this ligand.

Reactions of [Rh III Cl 2 Ph(SbPh 3 ) 3 ] 1 with an excess of purine-6-thione (C 5 H 4 N 4 S) or 1,3-thiazole (C 3 H 3 NS) in absolute ethanol gave crystalline [Rh III Cl 2 Ph(C 5 H 4 N 4 S)(SbPh 3 )] 2 (S trans to Sb), [Rh III Cl 2 Ph(SbPh 3 )(C 3 H 3 NS) 2 ] 3 and [Rh III Cl 2 Ph(SbPh 3 ) 2 (C 3 H 3 NS)] 4. The crystal structure of complex 2 has been determined. Two different rotamers, which differ in the orientation of the phenyl ligand around the Rh–C bond axis, are present. The co-ordination geometry of both molecules is pseudo-octahedral and the neutral, N 1 and N 9 protonated, purine ligand behaves as bidentate through S and N 7 . The Rh–N 7 bonding interaction is much weakened [average 2.262(7) A] by the high trans influence of the phenyl ligand. The H 8 atom of both purine systems points towards the centre of a phenyl ring of SbPh 3 . The geometrical parameters of the SbPh 3 molecules show that an attractive interaction between H 8 and the phenyl ring is operative for each rotamer. The 1 H NMR spectrum of 2, in DCON(CD 3 ) 2 , shows an upfield shift of 1.37 ppm for H 8 , consistent with a shielding effect from a phenyl ring of SbPh 3 . Therefore, the H 8 · · · Ph(Sb) attractive interaction exists also in solution. The crystal structure of 3 has also been determined. The co-ordination geometry is pseudo-octahedral, the metal being linked to two trans chloride ions, one antimony donor from SbPh 3 , one carbon atom from the phenyl ligand and two nitrogen atoms from thiazole ligands, one of which is trans to Ph [Rh–N 2.245(5) A]. The 1 H NMR spectrum shows that the solid-state structure is maintained in CDCl 3 solution. The signals of the H 2 and H 5 protons of the thiazole ligands are shifted downfield by 0.65 and 0.63 and 0.45 and 0.45 ppm for the molecules trans and cis to the C donor, respectively, upon complexation. The 1 H HMR spectrum of 4 is in agreement with the presence of a thiazole ligand trans to Ph. An interaction between the chloride ligands and some protons of the phenyl rings of SbPh 3 is resposible for a downfield chemical shift of about 0.2 ppm for the relevant 1 H NMR signals in compounds 1–4. Molecular mechanics analysis based on the crystal structures of 2 and 3 made it possible to set up force-field parameters suitable for this class of molecules. In the case of 3 the rotation of the SbPh 3 molecule around the Rh–Sb bond is highly hindered; the lowest barrier between minima is higher than 125 kJ mol -1 . The rotations of the thiazole ligands have minima consistent with the crystal structure.

Nitrile complexes of platinum easily hydrolyze to amidate, amide, and mixed amide–nitrile complexes. The amide ligands generally adopt the enol tautomeric form and coordinate to platinum through nitrogen. A mixed amide–nitrile complex, trans-[PtCl2{HN=C(OH)C(CH3)3}{N≡CC(CH3)3}] (trans-3), has shown to be the complex previously formulated as a platinum(IV) dichlorobisamidate derivative having the two amidate ligands in different tautomeric forms. The structure of trans-3 has been solved by single-crystal diffraction. The complex crystallizes in the Pbcn space group. The crystal structure has strong similarities with that previously reported by some of us for trans-[PtCl2{HN=C(OH)C(CH3)3}2] [R. Cini, F.P. Fanizzi, F.P. Intini, C. Pacifico, G. Natile, Inorg. Chim. Acta 264 (1997) 279]. Triplets of complex molecules are stabilized by intra-molecular hydrogen bonds involving N, Cl and O atoms.