Intermolecular potential energy surface and spectra of He-HCl with generalization to other rare gas-hydrogen halide complexes

A two-dimensional (rigid monomer) intermolecular potential energy surface (PES) of the He-HCl complex has been obtained from ab initio calculations utilizing the symmetry-adapted perturbation theory (SAPT) and an spdfg basis set including midbond functions. The bond length in HCl was chosen to be equal to the expectation value in the ground vibrational state of isolated HCl. The rigid-monomer potential should be a very good approximation to the complete (three-dimensional) potential for H-Cl distances corresponding to the lowest vibrational levels of the monomer since the He-HCl interaction energy was found to be only weakly dependent on the HCl bond length in this region, at least as compared to systems such as Ar-HF. The calculated points were fitted using an analytic function with ab initio computed asymptotic coefficients. As expected, the complex is loosely bound, with the dispersion energy providing the majority of the attraction. Our SAPT PES agrees with the semiempirical PES of Willey et al. [J. Chem. Phys. 96, 898 (1992)], in finding that, atypically for rare gas-hydrogen halide complexes including the lighter halide atoms, the global minimum is on the Cl side (with intermonomer separation 3.35 A and depth of 32.8 cm(-1)), rather than on the H side, where there is only a local minimum (3.85 A, 30.8 cm(-1)). The ordering of the minima was confirmed by single-point calculations in larger basis sets and complete basis set extrapolations, and also using higher levels of theory. We show that the opposite findings in the recent calculations of Zhang and Shi [J. Mol. Struct: THEOCHEM 589, 89 (2002)] are due to the lack of midbond functions in their basis set. Despite the closeness in depth of the two linear minima, the existence of a relatively high barrier between them invalidates the assumption of isotropy, a feature of some literature potentials. The trends concerning the locations of minima within the family of rare gas-hydrogen halide complexes are rationalized in terms of the physical components of the intermolecular forces and related to monomer properties. The accuracy of the SAPT PES was tested by performing calculations of rovibrational levels. The transition frequencies obtained were found to be in excellent agreement (to within 0.02 cm(-1)) with the measurements of Lovejoy and Nesbitt [J. Chem. Phys. 93, 5387 (1990)]. The SAPT PES predicts a dissociation energy for the complex of 7.74 cm(-1) which is probably more accurate than the experimental value of 10.1+/-1.2 cm(-1). Our analysis of the ground-state rovibrational wave function shows that the He-HCl configuration is favored over the He-ClH configuration despite the ordering of minima. This is due to the greater volume of the well in the former case. We have also determined positions and widths of three low-lying resonance states through scattering calculations. These predictions are expected to be more accurate than values derived from experiment.     

Four New Podocarpane‐Type Trinorditerpenes from Aleurites moluccana

Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC₅₀ value of 4.24 μg/ml.     

The design of boronic acid spectroscopic reporter compounds by taking advantage of the pK(a)-lowering effect of diol binding: nitrophenol-based color reporters for diols

The complex that forms between a boronic acid and a diol is often much more acidic than the starting boronic acid. In conditions where the solution pH is between the two pK(a) values, the boron atom will convert from a neutral trigonal form to an anionic tetrahedral form upon complexation. Such a change is likely to dramatically alter the electron density of neighboring groups. Utilizing this effect, we have designed and synthesized two nitrophenol-based boronic acid reporter compounds that change ionization states and therefore spectroscopic properties upon diol binding. Both compounds show significant UV changes upon addition of saccharides. For example, a blue shift of the absorption max from 373 to 332 nm was observed with the addition of D-fructose to 2-hydroxy-5-nitrophenylboronic acid at neutral pH. Such a reporter compound can be used as a recognition and signaling unit for the construction of polyboronic acid sensors for the selective and specific recognitions of saccharides of biological significance.     

Solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes under high-speed vibration milling

The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C₆₀(CH₂N(CH₃)CHR), R=H (4a), C₆H₅ (4b), p-NO₂-C₆H₄ (4c), p-CH₃O-C₆H₄ (4d), p-(CH₃)₂N-C₆H₄ (4e)) were obtained in moderate yields from reactions of C₆₀ with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C₆₀ with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C₇₀ with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines.     

金属—血清白蛋白的结构研究——Ⅵ.等离子点附近HSA和BSA中Cu(Ⅱ)和Ni(Ⅱ)金属中心的结构

本文用紫外光谱研究了等离子点附近HSA或BSA ¹Cu(Ⅱ)或Ni(Ⅱ)金属中心的结构。结果表明:在pH₄.0～5.3时,Cu(Ⅱ)—HSA配合物在低浓度时独具五配位的四方锥构型,高浓度时(>10^-4mol·l^-1)为四配位的四方平面构型,Cu(Ⅱ)—BSA、Ni(Ⅱ)—BSA在上述pH范围内均只存在四方平面构型。Cu(Ⅱ)、Ni(Ⅱ)结合位置与生理pH下的相同,均在白蛋白的N端三肽段上,与Asp^{1相似文献}   

Multilayer vesicles and vesicle clusters formed by the fullerene-based surfactant C60(CH3)5K

The self-assembly behavior of a fullerene-based surfactant, C60(CH3)5K, in water was studied using a combination of static and dynamic light scattering, as well as transmission electron microscopy, and compared to that of the compound C60(C6H5)5K. Both fullerene surfactant systems spontaneously assemble into large vesicles consisting of closed spherical shells formed by bilayers, with critical aggregation concentrations (CAC) lower than 10(-6) g ml(-1). At low concentrations, the aggregate sizes of C60(CH3)5K (radius R approximately 26.8 nm) and C60(C6H5)5K (R approximately 17.0 nm) were found to be substantially different from each other, showing that the change of the substituents surrounding the polar cyclopentadienide head group makes it possible to control the size of the resulting aggregates. Furthermore, the C60(CH3)5K vesicles were found to exist in two qualitatively different types of aggregation with a critical reaggregation concentration (CRC) located at 3.30 x 10(-6) g ml(-1). Above the CRC, larger aggregates were observed (R approximately 37.6 nm), showing a more complex form of supramolecular aggregation, e.g., in terms of multi-bilayer vesicles and/or of clusters of bilayer vesicles.     

Theoretical Studies on Reaction Mechanisms of HNCS with NH （ X^3∑）

The reaction mechanisms of HNCS with NH（X^3∑ ） were theoretically investigated. The minimum energy paths （MEP） of the reaction were calculated by using the density functional theory（DFT） at the B3LYP/6-311 ＋ ＋ G^＊＊ level. The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zeropoint energies（ZPE） of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD（T）/6-311 ＋ ＋ G^＊ ＊ level. It was found that the mechanisms of the HNCS ＋ NH（X^3∑） reaction involve two channels producing the HNC ＋ HNS and the N2H2 ＋ CS products. Channel 1 plays a dominant role and the HNC ＋ HNS are the main preduets. The reaction is exothermie.     

N,N''''-硝基苯酰基取代苯酰氨基硫脲的合成与生物活性

酰氨基硫脲类化合物不仅具有广谱抗菌性能 ,还具有极好的杀虫和植物生长调节活性 [1～ 3] ,因而引起许多国内外学者对硫脲类化合物的合成及其化学结构与生物活性关系方面的研究 [4～ 8] .为了进一步研究不同的取代基团对此类化合物生物活性的影响 ,作者用硝基苯酰基异硫氰酸酯与芳基酰肼加成制得相应的 N ,N -硝基苯酰基取代苯酰氨基硫脲 ( ) ,并初步测定了它们抑制大肠杆菌和枯草杆菌生长的生物活性 .这些化合物尚未见文献报道 .Ar— COCl KSCN Ar—CONCS a～ cAr CONHNH2 ( 1 ～ 7) Ar—CONHC( S) NHNHCOAr Ar:a.o-N…     

Hf[N(SO2C8F17)2]4-catalyzed Friedel-Crafts acylation in a fluorous biphase system

In a fluorous biphase system, Hf[N(SO₂C₈F₁₇)₂]₄ complex (1 mol %) catalyzes Friedel-Crafts acylation of aromatic compounds such as anisole, toluene and chlorobenzene, and the corresponding aromatic ketones are obtained in satisfactory to high yields. The catalyst is selectively soluble in lower fluorous phase and can be easily recovered by simple phase separation. Furthermore, the catalyst can be reused without decrease of activity in most cases.     

Reversed stereoselectivity in iodohydroxylation of allenyl sulfides. An efficient synthesis of (Z)-3-organosulfur-2-iodo-2-propenols

[reaction: see text] It is observed that the iodohydroxylation of 1,2-allenyl sulfides with I(2) and water in aqueous acetone showed Z-selectivity, which is opposite to that of the iodohydroxylation of 1,2-allenyl sulfoxides.