Radical-initiated alkene hydroauration as a route to gold(III) alkyls: an experimental and computational study

The hydroauration of functionalised 1-alkenes by the gold(III) hydride (C^NOMe^C)AuH is initiated by organic radicals and proceeds via (C^N^C)Au(II) radical intermediates following a bimolecular outer-sphere mechanism. The outcome of these reactions is determined by the stability of the gold-substituted radicals. The reaction is sensitive to steric as well as electronic factors; disubstituted alkenes and alkenes that form unstable radicals give product mixtures or are unreactive. As DFT calculations show, the reactions agree well with the calculated reaction enthalpies and the standard free energy change for the reaction of the gold(II) radical with the respective alkene

Synthesis, Structures and Properties of Luminescent (C^N^C)gold(III) Alkyl Complexes: Correlation between Photoemission Energies and C-H Acidity

The reaction of (C^Npz^C)AuCl with C-H acidic compounds H2CR1R2 in the presence of base readily affords the corresponding alkyl complexes (C^Npz^C)AuCHR1R2 [2a, R1 = R2 = CN; 3a, R1 = R2 = C(O)Me; 4, R1 = R2 = CO2Et; 5, R1 = R2 = C(O)Ph; 6a, R1 = H, R2 = C(O)Me]. The analogous pyridine-pincer complexes 2b, 3b and 6b were obtained similarly [C^Npz^C = 2,6-bis(4′-tBuC6H3)2pyrazine dianion; C^Npy^C = 2,6-bis(4′-tBuC6H3)2pyridine dianion]. The reactions of (C^Npz^C)AuOAcF (7a) and (C^Npy^C)AuOAcF (7b) with MeMgI gave the methyl complexes (C^Npz^C)AuMe (8a) and (C^Npy^C)AuMe (8b), respectively. The crystal structures of 2a, 2b, 3a, 6a, and 7a have been determined. The photophysical properties of the new complexes and those of the previously reported gold hydride (C^Npz^C)AuH (AuH) are reported. The lower-energy absorption and the emission maxima follow the energy sequence 2a < 3a < 4 < 5 < 6a < AuH ≈ 8a for the pyrazine series, and 2b < 3b < 6b ≈ 8b for the pyridine series. These values provide a correlation with the pKa values of the corresponding ancillary ligand precursors. In agreement with DFT calculations, the emissions are assigned to 3IL(C^N^C)/3ILCT {(C6H4tBu-4’)→pz/py*} transitions, dominated by the HOMO and the LUMO orbitals. The LUMO is located in the heterocycle (py/pz) in trans position to the ancillary ligand, which makes this orbital more sensitive to the electronic nature of the ancillary ligand than the HOMO. The calculations establish that the charge transfer from the tBuC6H3 ligand fragments to the central heterocycle ring in the dominant transition explains the modulation of the properties with the σ-donor characteristics of the alkyl or hydride ligands

Apricot melanoidins prevent oxidative endothelial cell death by counteracting mitochondrial oxidation and membrane depolarization

The cardiovascular benefits associated with diets rich in fruit and vegetables are thought to be due to phytochemicals contained in fresh plant material. However, whether processed plant foods provide the same benefits as unprocessed ones is an open question. Melanoidins from heat-processed apricots were isolated and their presence confirmed by colorimetric analysis and browning index. Oxidative injury of endothelial cells (ECs) is the key step for the onset and progression of cardiovascular diseases (CVD), therefore the potential protective effect of apricot melanoidins on hydrogen peroxide-induced oxidative mitochondrial damage and cell death was explored in human ECs. The redox state of cytoplasmic and mitochondrial compartments was detected by using the redox-sensitive, fluorescent protein (roGFP), while the mitochondrial membrane potential (MMP) was assessed with the fluorescent dye, JC-1. ECs exposure to hydrogen peroxide, dose-dependently induced mitochondrial and cytoplasmic oxidation. Additionally detected hydrogen peroxide-induced phenomena were MMP dissipation and ECs death. Pretreatment of ECs with apricot melanoidins, significantly counteracted and ultimately abolished hydrogen peroxide-induced intracellular oxidation, mitochondrial depolarization and cell death. In this regard, our current results clearly indicate that melanoidins derived from heat-processed apricots, protect human ECs against oxidative stress

Complete Resolution of Retroperitoneal Lymphangioma with a Single Trial of OK-432 in an Infant

Retroperitoneal lymphangioma is extremely rare. Although these neoplasms are benign, they can grow progressively with subsequent compression and infiltration of the adjacent structures. Surgical excision is demanding when the lesion surrounds vital structures and it is generally fraught with a high recurrence and morbidity rate. We report the case of a huge retroperitoneal lymphangioma in a newborn treated successfully with intracystic injection of OK-432

What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach

The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern‐contemporary art, was investigated by a multi‐analytical approach. PF foams with open and closed‐cell structures were selected and analyzed in their unaged and naturally indoor‐aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro‐Fourier transform infrared spectroscopy (μ‐ FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open and closed‐cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ‐FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements.The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern‐contemporary art, was investigated by a multi‐analytical approach. PF foams with open-and closed‐cell structures were selected and analyzed in their unaged and naturally indoor‐aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro‐Fourier transform infrared spectroscopy (μ‐ FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open-and closed‐cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ‐FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements

Thermal diffusivity from Fourier’s inverse problem supervised by an optimization model: Theoretical analysis and experimental validation

An original experimental device coupled with an optimization technique, for determining the thermal diffusivity () of solid materials, has been devised and experimentally validated. The inverse problem of the classical Fourier heat equation in transient condition is numerically supervised by an optimization procedure for the initial and boundary conditions from measurements. Imperfect adiabaticity on the insulated lateral surfaces is explained by modeling heat loss correction functions with additional time dependent Robin conditions. The optimization model identifies the optimal values of the heat transfer coefficients and of by minimizing the residual function between the model predictions and the experimental data. Incorporating the heat loss corrections in the solution of the heat equation significantly improves the estimation of the . Indeed, the time profile of the surface temperatures measured for a specimen of PPMA material is well reflected by the simulated curves. The estimated is in good agreement with an experimental inter-comparison of eleven laboratories equipped with Laser Flash, hot disk, and hot bridge certified devices. Our results reveal a reliable capability of the model to identify the value that explains the functional dependence underlying the experimental observations. The error lies in the range 5% or 34%, depending on whether the heat losses are accounted or not

Chelating Phosphorus-An O, C, O-Coordinating Pincer-Type Ligand Coordinating PIII and PV Centres

The sequence of reactions of the phosphorus-containing aryllithium compound 5-t-Bu-1,3-[(P(O)(O-i-Pr)(2)](2)C6H2Li (ArLi) with Ph2PCl, KMnO4, elemental sulfur and elemental selenium, respectively, gave the aryldiphenylphosphane chalcogenides 5-t-Bu-1,3-[(P(O)(O-i-Pr)(2)](2)C6H2P(E)Ph-2 (1, E=O; 2, E=S; 3, E=Se). Compound 1 partially hydrolysed giving [5-t-Bu-1-{(P(O)(O-i-Pr)(2)}-3-{(P(O)(OH)(2)}C6H2]P(O)Ph-2 (4). The reaction of ArLi with PhPCl2 provided the benzoxaphos-phaphosphole [1(P), 3(P)-P(O)(O-i-Pr)OPPh-6-t-Bu-4-P(O)(O-i-Pr)(2)]C6H2P (5i) as a mixture of the two diastereomers. The oxidation of 5i with elemental sulfur gave the benzoxaphos-phaphosphole sulfide [1(P), 3(P)-P(O)(O-i-Pr)OP(S)Ph-6-t-Bu-4-P(O)(O-i-Pr)(2)]C6H2 (5) as pair of enantiomers P1(R), P3(S)/P1(S), P3(R) of the diastereomer (RS/SR)-5 (5b). The aryldiphenylphosphane 5-t-Bu-1,3-[(P(O)(O-i-Pr)(2)](2)C6H2PPh2 (6) was obtained from the reaction of the corresponding aryldiphenylphosphane sulfide 2 with either sodium hydride, NaH, or disodium iron tetracarbonyl, Na2Fe(CO)(4). The oxidation of the aryldiphenylphosphane 6 with elemental iodine and subsequent hydrolysis yielded the aryldiphenyldioxaphosphorane 9-t-Bu-2,6-(OH)-4,4-Ph-2-3,5-O-2-2,6-P-2-4 lambda(5)-P-[5.3.1.0]-undeca-1(10),7(11),8-triene (7). Both of its diastereomers, (RR/SS)-7 (7a) and (RS/SR)-7 (7b), were separated as their chloroform and i-propanol solvates, 7a.2CHCl(3) and 7b.i-PrOH, respectively. DFT calculations accompanied the experimental work

Isocyanide insertion into Au-H bonds: first gold iminoformyl complexes

Isocyanides insert into gold(III)-hydrogen bonds to give the first examples of gold iminoformyl complexes. The reaction is initiated by catalytic amounts of radicals; DFT calculations indicate that this is an equilibrium reaction driven forward by isocyanide in sufficient excess to trap the Au(II) intermediate