ADVERTISEMENT RETURN TO ISSUEPREVArticleSimple and hydrolyzable compounds in virgin olive oil. 3. Spectroscopic characterizations of the secoiridoid derivatives.Gianfrancesco. Montedoro, Maurizio. Servili, Maura. Baldioli, Roberto. Selvaggini, Enrico. Miniati, Alceo. MacchioniCite this: J. Agric. Food Chem. 1993, 41, 11, 2228–2234Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November...

This contribution details the synthesis and chemical/physical characterization of a series unconventional twisted pi-electron system electro-optic (EO) chromophores. Crystallographic analysis these chromophores reveals large ring-ring dihedral twist angles (80-89 degrees) highly charge-separated zwitterionic structure dominating ground state. NOE NMR measurements angle in solution confirm that solid-state twisting persists essentially unchanged solution. Optical, IR, spectroscopic studies...

The phenolic composition of peel, pulp, and seed the olive fruit was studied for several Italian cultivars used oil extraction. contained a compound never previously detected in peel pulp. spectroscopic characterization this proved, first time, presence nüzhenide seed. Study showed that oleuropein, demethyloleuropein, verbascoside were present all constitutive parts fruit; by contrast, exclusively seeds at ripening stages studied. Keywords: Nüzhenide; phenols; secoiridoids; NMR

Changing the counteranion along series Br, BF4, PF6, SbF6 in their ion-paired 2-pyridylmethyl imidazolium salts causes kinetic reaction products with IrH5(PPh3)2 to switch from chelating N-heterocyclic carbenes (NHCs) having normal C2 (N path) abnormal C5 binding (AN path). Computational work (DFT) suggests that AN path involves C-H oxidative addition Ir(III) give Ir(V) little anion dependence. The N path, contrast, goes by heterolytic activation proton transfer adjacent hydride. is...

We report on three Ir(iii) molecular catalysts for water oxidation: 1, [Cp*Ir(ppy)Cl]; 2, [Cp*Ir(bzpy)NO(3)]; 3, [Cp*Ir(H(2)O)(3)](NO(3))(2). 2 and 3 are water-soluble show a long-term activity ca. times higher than 1. It is remarkable that having the simplest structure, catalyst with highest activity.

The activity of three [Cp*IrLn] (Cp* = pentamethylcyclopentadienyl) archetypal catalysts ([Cp*Ir (bpy)Cl]Cl (1, bpy 2,2′-bipyridine), [Cp*Ir(bzpy)(NO3)] (2, bzpy 2-benzoylpyridine) and [Cp*Ir(H2O)3](NO3)2 (3)) for water oxidation to molecular oxygen was compared using cerium(IV) ammonium nitrate as a sacrificial oxidant. Kinetic studies were carried out by: i) measuring the depletion Ce4+ through UV-Vis spectroscopy, ii) directly detecting evolved Clark electrode iii) volume oxygen. kinetics...

The relative anion-cation orientation in [(PPh(3))Au(4-Me-styrene)]BF(4) (1BF(4)) and [(NHC)Au(4-Me-styrene)]BF(4) [2BF(4); NHC = 1,3-bis(di-iso-propylphenyl)-imidazol-2-ylidene] has been investigated by combining (19)F,(1)H-HOESY NMR spectroscopy Density Functional Theory (DFT) calculations incorporating solvent relativistic effects. It found that BF(4)(-) locates on the side of 4-Me-styrene, close to olefin region is opposite 4-Me-Ph moiety 1BF(4). In 2BF(4), counterion approaches cation...

The synthesis and characterization of two neutrally charged Ni(II) ethylene polymerization catalysts, [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl)phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CH3)FI-Ni) [2-tert-butyl-6-((2,6-(3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]nickel(II) ((CF3)FI-Ni) are reported. In the presence a Ni(COD)2 cocatalyst, these catalysts produce markedly different polyethylenes: densely branched oligomers with Mw = 1.4 × 103 g mol–1...

Molecular hydrogen (H 2 ) is considered an ideal energy vector and a clean fuel, due to its zero-carbon combustion. Nevertheless, despite the most one of abundant elements in universe earth crust, respectively, it always combined with other our planet never appears elemental state. This means that H must be produced through, almost always, endergonic processes, whose sustainability depend not only on starting material but also source necessary for these processes occur. Colors have been...

Abstract Determining accurate molecular dimensions in water, from measured translational self‐diffusion coefficients ( D t ), is extremely important biochemistry, supramolecular chemistry, organometallic chemistry and beyond, but it still represents a big challenge especially for small medium‐sized molecules. Indeed, current semiempirical adaptations of the Stokes‐Einstein equation, which allow determination size solutes organic solvents, proved inadequate aqueous systems. To overcome such...

Abstract Phenolic compounds are the most important antioxidants of virgin olive oil. This paper reports on application solid phase extraction (SPE) in separation phenolic from fruit, oil, and by‐products mechanical oil complete spectroscopic characterization by nuclear magnetic resonance demethyloleuropein verbascoside extracted fruit. SPE led to a higher recovery olives than did liquid/liquid extraction. also was used separate pomaces vegetation waters. Phenylacid phenyl‐alcohol...

The solution structures of the metallocenium homogeneous polymerization catalyst ion-pairs [Cp(2)ZrMe](+)[MeB(C(6)F(5))(3)](-) (1), [(1,2-Me(2)Cp)(2)ZrMe](+)[MeB(C(6)F(5))(3)](-) (2), [(Me(2)SiCp(2))ZrMe](+)[MeB(C(6)F(5))(3)](-) (3), [Me(2)C(Fluorenyl)(Cp)ZrMe](+)[FPBA](-) (FPBA = tris(2,2',2' '-nonafluorobiphenyl)fluoroaluminate) (4), [rac-Et(Indenyl)(2)ZrMe](+)[FPBA](-) (5), [(Me(5)Cp)(2)ThMe](+)[B(C(6)F(5))(4)](-) (6), [(Me(2)SiCp(2))Zr(Me)(THF)](+)[MeB(C(6)F(5))(3)](-) (7),...

Nonlinear optics: Twisted π-electron system electrooptic (EO) chromophores with exceptional molecular hyperpolarizabilities (−488 000×10−48 esu at 1907 nm) were designed and synthesized. Crystallographic analysis reveals large twist angles a highly charge-separated zwitterionic ground state. Experiments on poled host–guest polymers containing these show them to be promising candidates for EO applications. Supporting information this article is available the WWW under...

The utility of PGSE NMR measurements in determining hydrodynamic radii (rH) and volumes (VH) small- medium-size molecules (3 Å < rH 6 Å) was evaluated by performing for a variety pure deuterated solvents their solutions containing the internal standard TMSS [tetrakis(trimethylsilyl)silane] also presence variable concentration 3BPh4. It found that accurate VH values can be obtained introducing Stokes−Einstein equation (Dt = kT/cπηrH) not only correct temperature (T) viscosity (η) but,...

Pyridyl-amido catalysts have emerged recently with great promise for olefin polymerization. Insights into the activation chemistry are presented in an initial attempt to understand polymerization mechanisms of these important catalysts. The C1-symmetric arylcyclometallated hafnium pyridyl-amido precatalysts, denoted Me2Hf{N(-),N,C(-)} (1, aryl = naphthyl; 2, phenyl), both Lewis (B(C6F5)3 and [CPh3][B(C6F5)4]) Brønsted ([HNR3][B(C6F5)4]) acids is investigated. Reactions 1 B(C6F5)3 lead...

(19)F,(1)H HOESY, diffusion, and temperature-dependent (19)F (1)H NMR studies allowed us to unequivocally probe the association between frustrated PR3/B(C6F5)3 (1, R = CMe3; 2, 2,4,6-Me3C6H2) Lewis pairs in aromatic solvents. No preferential orientation is favored, as deduced by combining HOESY DFT results, suggesting via weak dispersion rather than residual acid/base interactions. The process slightly endoergonic [K 0.5 M(-1), ΔG(0)(298 K) +0.4 kcal/mol for 2], derived from diffusion measurements.

Reactions of [{N−,N,Cnaphthyl−}HfMe][MeB(C6F5)3] (2) precatalyst with a series α-olefins have been investigated in order to intercept the active polymerization species generated by an situ modification precursor insertion single monomer unit into Hf−CAryl bond. In all cases first migratory occurs bond rather than Hf−CAlkyl A low-temperature 170 equiv 1-hexene activated tris(pentafluorophenyl)borane (FAB) allows for complete NMR characterization Hf−CAlkylaryl methyl cation. This structure...

The intra- and interionic structures of a mononuclear phosphine gold(I) alkyne complex [(PAr(F)(3))Au(2-hexyne)]BF(4) [1BF(4); Ar(F) = 3,5-bis(trifluoromethyl)phenyl] its analogous [(NHC)Au(2-hexyne)]BF(4) [2BF(4); NHC 1,3-bis(diisopropylphenyl)imidazol-2-ylidene] have been investigated by combining 1D 2D multinuclear NMR spectroscopy density functional theory calculations. It has found that in 1BF(4) is depleted electron to greater extent than 2BF(4). This correlates with the...

In this contribution we report a comparative analysis of the chemical bond between an N-heterocyclic carbene and different Au(I) metal fragments general formula [(NHC)AuL]+ or [(NHC)AuL], where NHC is imidazol-2-ylidene L chosen from some ligands frequently used both in coordination organometallic chemistry. The focus on nature Au(I)–C (of NHC) terms Dewar–Chatt–Duncanson components its modulation by ancillary ligand L. case = Cl (metal fragment AuCl), present binding mode with...

Organometallic compounds [Cp*Ir(κ2-N,O)X] (κ2-N,O = 2-pyridinecarboxylic acid, ion(−1) (1), 2,4-pyridinedicarboxylic (2), 2,6-pyridinedicarboxylic (3); X– Cl– (a), NO3– (b)) and [Ir(κ3-N,O,O)(1-κ-4,5-η2-C8H13)(MeOH)] (κ3-N,O,O ion(−2) (4)) are effective catalysts for the oxidative splitting of water to O2 driven by Ce4+. They show similar TOFLT values (long-term TOF, 2.6–7.4 min–1) while TOFIN (initial TOF) strongly depend on catalyst (1 ≫ 2 > 3 4), reaching a maximum value 287 min–1 (4.8...

Abstract The reaction between H 2 O and two water oxidation catalysts {[Cp*Ir(H O) 3 ](NO ) ( 1 , Cp* = pentamethylcyclopentadienyl) [Cp*Ir(bzpy)(NO )] bzpy 2‐benzoylpyridine)} was studied by means of in situ 1D‐ 2D‐NMR experiments order to elucidate if catalyst degradation proceeds through the initial functionalization a quaternary carbon atom (C‐attack) or hydrogen abstraction (H‐attack) –C–CH moiety. It shown that underwent double moiety leading formation –C(OR)–CH OR (R OH) strictly...

The substitution of a methyl to an octyl group in the ancillary triazolylidene ligand—an apparently simple variation—induces more than 10-fold increase activity corresponding iridium complex water oxidation catalysis when using cerium(IV) as sacrificial oxidant. Detailed NMR studies suggest that various different molecular species form, all bearing intact ligand. substituent is essential for inducing association species, thus generating extraordinarily active multimetallic catalytic sites....

Abstract We critically review recent experimental and theoretical investigations into some key aspects of the chemistry gold(I) complexes type [L–Au–S] + X – (L = NHC carbenes phosphanes, S alkenes alkynes, weakly coordinating counterion). These systems are important intermediates formed during gold‐catalyzed nucleophilic additions to an unsaturated substrate, their specific activity is largely governed by two fundamental factors: nature gold–substrate bond role ion‐pair structure in...