Conductance study of association in aqueous CaCl2, Ca(CH3COO)2, and Ca(CH3COO)2.nCH3COOH from 348 to 523 K at 10 MPa

The conductances of aqueous CaCl2, Ca(CH3COO)2, and Ca(CH3COO)2.nCH3COOH were measured from 348 to 523 K at pressures near 10 MPa using a flow conductometric technique. The first association constant for calcium chloride and the first and second association constants for calcium acetate in water, were derived from a least-squares fit of the measurements to a conductance model in which activity coefficients were calculated using the mean spherical approximation (MSA) and the conductance was modeled by the Turq, Blum, Bernard, and Kunz (TBBK) equation, plus a mixture model.     

An atom efficient and solvent-free synthesis of structurally diverse amides using microwaves

An array of structurally diverse amides was synthesized efficiently by combining (primary and secondary) amines and carboxylic acids in one-pot under solvent-free microwave (MW) conditions. In most cases, no racemization was observed with optically active inputs and chiral amides were obtained in high ee or de.     

Adapting decarbonylation chemistry for the development of prodrugs capable of in vivo delivery of carbon monoxide utilizing sweeteners as carrier molecules

Carbon monoxide as an endogenous signaling molecule exhibits pharmacological efficacy in various animal models of organ injury. To address the difficulty in using CO gas as a therapeutic agent for widespread applications, we are interested in developing CO prodrugs through bioreversible caging of CO in an organic compound. Specifically, we have explored the decarboxylation–decarbonylation chemistry of 1,2-dicarbonyl compounds. Examination and optimization of factors favorable for maximal CO release under physiological conditions led to organic CO prodrugs using non-calorific sweeteners as leaving groups attached to the 1,2-dicarbonyl core. Attaching a leaving group with appropriate properties promotes the desired hydrolysis–decarboxylation–decarbonylation sequence of reactions that leads to CO generation. One such CO prodrug was selected to recapitulate the anti-inflammatory effects of CO against LPS-induced TNF-α production in cell culture studies. Oral administration in mice elevated COHb levels to the safe and efficacious levels established in various preclinical and clinical studies. Furthermore, its pharmacological efficacy was demonstrated in mouse models of acute kidney injury. These studies demonstrate the potential of these prodrugs with benign carriers as orally active CO-based therapeutics. This represents the very first example of orally active organic CO prodrugs with a benign carrier that is an FDA-approved sweetener with demonstrated safety profiles in vivo.

1,2-Dicarbonyl compounds with FDA-approved sweeteners as leaving groups deliver CO for protection against acute kidney injury in mice.     

Inverse electron demand hetero-Diels–Alder reaction in preparing 1,4-benzodioxin from o-quinone and enamine

A process for synthesizing 1,4-benzodioxin, through oxidation of a phenol to an o-quinone followed by treatment with an enamine, has been developed. Adduct stereochemistry is found to be retained via this one-pot reaction. The method uses hypervalent iodine reagent under mild conditions and is compatible with a wide scope of phenols and enamines.     

An Isolable Radical Anion Featuring a 2-Center-3-Electron π-Bond without a Clearly Defined σ-Bond

Featuring an extra electron in the π* antibonding orbital, species with a 2-center-3-electron (2c3e) π bond without an underlying σ bond are scarcely known. Herein, we report the synthesis, isolation and characterization of a radical anion salt [K(18-C-6)]⁺{[(HCNDipp)₂Si]₂P₂}⋅⁻ (i.e. [K(18-C-6)]⁺ 3 ⋅⁻) (18-C-6=18-crown-6, Dipp=2,6-diisopropylphenyl), in which 3 ⋅⁻ features a perfectly planar Si₂P₂ four-membered ring. This species represents the first example of a Si- and P-containing analog of a bicyclo[1.1.0]butane radical anion. The unusual bonding motif of 3 ⋅⁻ was thoroughly investigated via X-ray diffraction crystallography, electron paramagnetic resonance spectroscopy (EPR), and calculations by density functional theory (DFT), which collectively unveiled the existence of a 2c3e π bond between the bridgehead P atoms and no clearly defined supporting P−P σ bond.     

Orientation and conformation of two [6]carbohelicenes in stretched polystyrene and a thermoresponsive polyaspartate

Two functionalized [6]carbohelicenes, one of which was also available in its two enantiomeric pure forms, were oriented in stretched polystyrene in CDCl₃, and in a recently introduced chiral thermoresponsive lyotropic polyaspartate (poly(benzyl)_0.5(phenethyl)_0.5-L-aspartate) in C₂D₂Cl₄. From the resulting ¹H,¹³C residual dipolar couplings, the helical pitch of a methylated [6]carbohelicene was determined and found to be in agreement with theoretical predictions and existing crystal structures (d(C2,C2′) ≈ 4.3 Å). For a second [6]carbohelicene with para-methoxyphenyl substituents, a clear conformational preference of the substituents was observed. The orientational properties of the two helicene enantiomers in the chiral polyaspartate are very similar, but both drastically change around 306 K. We suggest this behavior is due to an unusual phase transition in the liquid crystal.     

GaAs(100)解理面的能带弯曲

在真空中解理后,用XPS测得了GaAs样品（110）断面能带弯曲的动态过程．两组重掺杂n型和p型GaAs样品的费米能级分别向禁带中间的方向移动了0.4eV和0．3eV.实验测得重掺杂n型和p型GaAs样品费米能级之差为1．3eV,它们的禁带宽度理论值为1．42eV,这说明结果是合理的．根据实验结果,对引起GaAs表面能带弯曲的可能原因进行了分析讨论．排除了本征表面态、真空中残留气体和X射线辐射等原因,认为解理过程在表面产生的缺陷和解理后表面晶格弛豫过程中产生的缺陷可能是导致能带弯曲的主要原因．