Theoretical study on the structure and energetics of alkali halide clusters

The structures of alkali halide clusters Na_nF_n, Li_nF_n and Na_nCl_n, and their metal-excess clusters Na_nF_n−1⁺, Li_nF_n−1⁺ and Na_nCl_n−1⁺ were investigated by the ab initio molecular orbital method for cluster sizes from 1 to 14. The magic numbers for the neutral clusters Na_nF_n, Li_nF_n and Na_nCl_n are 4, 6, and 8. The most stable structure for these cluster sizes is a perfect crystallite for Na_nF_n and Na_nCl_n, and a double ring for Li_nF_n. The magic numbers for the metal-excess clusters are 5 and 8, which are near ideal cuboids with (100) facets.     

Thermodynamics of (1,4-difluorobenzene + an n-alkane) and of (hexafluorobenzene + an n-alkane)

Excess molar enthalpies H^E and excess molar volumes V^E have been measured, as a function of mole fraction x₁, at 298.15 K and atmospheric pressure for the five liquid mixtures (x₁1,4-C₆H₄F₂ + x₂n-C_lH_2l+2), l = 7, 8, 10, 12 and 16. In addition, H^E and excess molar heat capacities C_P^E at constant pressure have been determined for the two liquid mixtures (x₁C₆F₆ + x₂n-C_lH_2l+2), l = 7 and 14, at the same temperature and pressure. The instruments used were flow microcalorimeters of the Picker design (the H^E version was equipped with separators) and a vibrating-tube densimeter, respectively.

The excess enthalpies of the five difluorobenzene mixtures are all positive and quite large; they increase with increasing chain length l of the n-alkane from H^E(x₁ = 0.5)/(J mol⁻¹) = 1050 for l = 7 to 1359 for l = 16. The corresponding excess volumes V^E are all positive and also increase with increasing l: V^E(x₁ = 0.5)/(cm³ mol⁻¹) = 0.650 for l = 7 and 1.080 for l = 16. Interestingly, the excess enthalphies of the corresponding mixtures with hexafluorobenzene are only about 5% larger, whereas the excess volumes of (x₁C₆F₆ + x₂n-C_lH_2l+2) are roughly twice as large as those of their counterparts in the series containing 1,4-C₆H₄F₂. Specifically, at 298.15 K H^E(x₁ = 0.5)/(J mol⁻¹) = 1119 for (x₁C₆F₆ + x₂n-C₇H₁₆) and 1324 for (x₁C₆F₆ + x₂n-C₁₄H₃₀), and for the same mixtures V^E(x₁ = 0.5)/(cm³ mol⁻¹) = 1.882 and 2.093, respectively. The excess heat capacities for both systems are negative and of about the same magnitude as the excess heat capacities of mixtures of fluorobenzene with the same n-alkanes (Roux et al., 1984): C_P^E(x₁ = 0.5)/(J K⁻¹ mol⁻¹) = −1.18 for (x₁C₆F₆ + x₂n-C₇H₁₆), and −2.25 for (x₁C₆F₆ + x₂n-C₁₄H₃₀). The curve C_P^E vs. (x₁ for x₁C₆F₆ + x₂n-C₁₄H₃₀) shows a sort of “hump” for x₁ 0.5, which is presumed to indicate emerging W-shape composition dependence at lower temperatures.     

Thermodynamic studies of the solvation of Ph4AsPh4B in mixed solvents (MeOH—DMF)

The thermodynamic data (ΔG⁰, ΔH⁰ and TΔS⁰) of the solvation of tetraphenylarsonium-tetraphenylborate (Ph₄AsPh₄B) and its neutral parts, tetraphenylgermanium (Ph₄Ge) and tetraphenylmethane (Ph₄C) in methanol—N,N-dimethylformamide mixed solvents are discussed.

The values of the free energy of transfer, Δ^s_MG⁰, are calculated from measurements of the solubilities of Ph₄AsPh₄B, Ph₄Ge and Ph₄C in the successive fractions of MeOH in DMF at three different temperatures (15, 25, 35°C). The values of Δ^s_MH⁰ and TΔ^s_MS⁰ for the derivatives are calculated from Δ^s_MG⁰ values.

The values of Δ^s_MG⁰, Δ^s_MH⁰ and TΔ^s_MS⁰ of tetraphenylarsonium and tetraphenylborate ions have also been carefully calculated. The ratios of Δ^s_MG⁰ values (Δ^s_MG⁰ = ΔG⁰(+)/ΔG⁰(−)) were found to be greater than unity. Similarly, the ratios of Δ^s_MH⁰ and TΔ^s_MS⁰ for the positive and negative ions were found to be greater than unity.     

The effect of terminal chain modifications on the mesomorphic properties of 4,4'-disubstituted diphenyldiacetylenes

A variety of terminal chain modifications (Y) were made on the diacetylenes in which X=C_nH_2n+1, C₁₂H₂₅O and F, and Y=CH₂CH(Me)C₂H₅, COCH₃, C≡CC₅H₁₁, C_nF_2n+1C_nH_2n+1 and CH=CHCO₂C₃H₇. Mesomorphic properties were determined by hot stage polarizing microscopy and DSC. These were compared with those for the dialkyl analogues (X=C_mH_2m+1, Y=C_nH_2n+1) and a series of 1- and 2-olefins (Y=CH=CHC_nH_2n+1 and CH₂CH=CHC_nH_2n+1). The 1-olefin series showed wider range nematics than the dialkyl compounds, whereas the above modifications showed either narrow range nematic phases, no mesophase or higher melting temperatures. New transition temperature and enthalpy data are provided for some of the dialkyl and F-alkyl compounds previously reported, for comparisons. Preliminary birefringence data are also included along with the results of some heat and UV stability studies.     

MECHANISM OF PHYSICAL QUENCHING OF SINGLET MOLECULAR OXYGEN BY CHLOROPHYLLS and RELATED COMPOUNDS OF BIOLOGICAL INTEREST

Abstract— The rate constant k₅/ > for physical quenching of singlet oxygen O₂(δ₁;) by the sensitizer in dye-sensitized photooxygenations is determined in the case of chlorophylls a and b (7.3 times 10⁸, 4.2 times 10⁸ M^-1 s^-1 respectively), pheophytins a and b (7.4 times 10⁷, 3.0 times 10⁷ M^-1 s^_1 respectively), tetraphenylporphyrin (4.4 times 10⁷ M^-1 s^_1), magnesium tetraphenylporphyrin (5.0 times 10⁸ M^-1 s^_1), zinc tetraphenylporphyrin (1.5 times 10⁸ M^-1 s^_l) and protoporphyrin IX-dimethylester (9.1 times 10⁷ M ^-1 s^_1) in benzene. These sensitizers show a linear correlation between log k_s^O , and their half-wave oxidation potentials and the value of the slope is similar to that observed for various compounds such as phenols. It is concluded that (i) the interaction between chlorophylls and related compounds with singlet oxygen may involve an exciplex as for phenols, and (ii) physical quenching may be envisaged as a spin-orbit-induced intersystem crossing within the exciplex.     

钒取代的Dawson型磷钼酸对酪氨酸酶的抑制作用

采用酶动力学方法研究了5种钒取代的Dawson型磷钼酸H₇[P₂Mo₁₇VO₆₂]、H₈[P₂Mo₁₆V₂O₆₂]、H₉[P₂Mo₁₅V₃O₆₂]、H₈[P₂Mo₁₄V₄O₆₂H₂]和H₉[P₂Mo₁₃V₅O₆₂H₂](分别简写为P₂Mo₁₇V、P₂Mo₁₆V₂、P₂Mo₁₅V₃、P₂Mo₁₄V₄和P₂Mo₁₃V₅)对蘑菇酪氨酸酶二酚酶的抑制作用,结果表明,效应物P₂Mo₁₇V、P₂Mo₁₆V₂和P₂Mo₁₅V₃能够明显地抑制酪氨酸酶的活性,其半抑制浓度(IC₅₀)值分别为0.409、0.386和0.386 mmol/L,且均表现为可逆的竞争型抑制,效应物P₂Mo₁₇V、P₂Mo₁₆V₂和P₂Mo₁₅V₃对游离酶的抑制常数K_I分别为0.234、0.391和0.249 mmol/L。 而效应物P₂Mo₁₄V₄在0~1.0 mmol/L浓度范围内,对酪氨酸酶二酚酶无明显抑制作用,效应物P₂Mo₁₃V₅对酪氨酸酶二酚酶表现为激活作用。     

Mössbauer spectroscopic and magnetic properties of iron/III/ pheophytins

Mössbauer spectra of /pheophytinato a/ iron/III/ chloride [Fe/Pheo-a/Cl] and /pheophytinato b/ iron/III/ chloride [Fe/Pheo-b/Cl] have revealed that the central iron/III/ ion is in a high-spin state and axially coordinated by chloride ions in solid phase. Temperature-dependent asymmetry observed for the quadrupole splitting doublet of iron/III/ pheophytins, i.e., Fe/Pheo-a/Cl and Fe/Pheo-b/Cl, is interpreted on the basis of the zero-field splitting. The structural difference between iron/III/ pheophytins and iron/III/ porphyrins is reflected in the quadrupole splitting more than in the isomer shift. Magnetic behaviour of iron/III/ pheophytins near 4.2 K is very similar to that of iron/III/ porphyrins.     

The interaction between C28 (Td) and X (X=H and F)

Hydrogen and fluorine addition reactions with C₂₈(T_d) have been investigated by the density function theory method at B3LYP/6-31G level. The interaction potential between C₂₈(T_d) and atom X (X=H and F) shows that there are three possible stable isomers of C₂₈(T_d)X (X=H and F) and the average binding energy calculations suggest that C₂₈(T_d)H₄ is the most stable hydrogen adduct among C₂₈(T_d)H_n (n=1–28). Furthermore, by comparisons of the energy between C₂₈(T_d)H and C₂₈(C_s)H we found that the former are more stable than the later, and the structural and energy analysis further indicate that C₂₈(C_s)H is only with a small distortion of C₂₈(T_d)H symmetry. In addition, the transition states, as well as reaction pathways of X transfer reactions between different key points on C₂₈(T_d) representative patch are given to explore the possible reaction mechanism.     

Coordination-driven self-assembly of palladium(Ⅱ)-based metallacalixarenes as anion receptors using flexible pyridine-bridged diimidazole ligands

Two types of palladiu m(Ⅱ)-based metallacalixarenes[ML]²⁺and[ML₂]²⁺have been synthesized through coordination-driven self-assembly from a series of flexible pyridine-bridged diimidazole ligands[2,6-bis((1 H-imidazol-1-yl)methyl)pyridine(L¹),2,6-bis((1 H-benzo[d]imidazol-1-yl)methyl)pyridine(L²),2,6-bis((1 H-naphtho[2,3-d]imidazol-1-yl)methyl)pyridine(L³)],with palladium(II)-based building blocks[Pd(BF₄)₂(M¹-BF_4)and(tmeda)Pd(NO₃)₂(M²-NO₃)(tmeda=N,N,N',N'-tetramethyl-ethylenediamine)].All complexes were characterized by NMR spectroscopy(¹H NMR and¹³C NMR),mass spectrometry(CSIMS,ESI-HRMS)and elemental analysis.The single crystal X-ray diffraction analysis of[M¹L²_2](NO₃)₂,[M¹L³_2](NO₃)₂,[M¹L³_2](PF_6)_2 and[M~2 L³](NO₃)₂further confirmed the uniquely single bowl-shape and double bowl-shape structures.The anion binding properties within the metallacalixarenes as receptors were also investigated by NMR titration experiments in DMSO.     

Determination of the enthalpy change for anabolism by four methods

The enthalpy change for anabolism is needed to model the growth/respiration relation in plants. If all CO₂ production is assigned to catabolism, the anabolic reaction becomes C_substrate→C_products+xO₂ with an enthalpy change, ΔH_b. Four methods are proposed for determining ΔH_b: (a) From the difference in the heats of combustion of substrate and anabolic products (i.e. newly grown tissue). (b) From the composition of newly grown tissue and application of Thornton’s rule. (c) From independently measured values of the specific growth rate, R_SG, and of the product (R_SG ΔH_b). The product (R_SG ΔH_b) equals (−ΔH_CO2R_CO2−R_q) where R_CO2 is the specific rate of CO₂ production by respiration, ΔH_CO2 is the heat of combustion of respiratory substrate per mole of CO₂ and R_q is the specific metabolic heat rate. ΔH_b is then calculated as the ratio (R_SG ΔH_b)/R_SG. (d) From (ΔH_b=−(R_q/R_CO2+ΔH_CO2) [(1−)/] where is the substrate carbon conversion efficiency obtained from a total carbon balance. The first three methods have been tested and compared on oat seedlings and the last on corn seedlings. ΔH_b values from all four methods are in reasonable agreement despite the different assumptions involved.     

New organogold(I) complexes: Synthesis, structure, and dynamic behavior of the polynuclear organogold diphenylmethane and diphenylethane derivatives

Two organogold derivatives of diphenylmethane and diphenylethane, Ph₃PAu(o-C₆H₄)CH₂(C₆H₄-o)AuPPh₃ (1) and Ph₃PAu(o-C₆H₄)(CH₂)₂(C₆H₄-o)AuPPh₃ (2), have been synthesized by the reaction of ClAuPPh₃ with Li(o-C₆H₄)CH₂(C₆H₄-o)Li and Li(o-C₆H₄)(CH₂)₂(C₆H₄-o)Li respectively. The interaction of 1 with dppe results in the replacement of the two PPh₃ groups to give a macrocyclic compound (3) that includes an Au Au bond. Compounds 1 and 2 react with one or two equivalents of [Ph₃PAu]BF₄ to form new types of cationic complex [CH₂(C₆H₄-o)₂(AuPPh₃)₃]BF₄ (4), [CH₂(C₆H₄-o)₂(AuPPh₃)₄](BF₄)₂ (5), and [(CH₂)₂(C₆H₄-o)₂(AuPPh₃)₄](BF₄)₂ (6). Complexes 1–6 have been characterized by X-ray diffraction studies, FAB MS, and IR as well as by ¹H and ³¹P NMR spectroscopy. A complicated system of Au H-C agostic interactions, involving the bridging alkyl groups (—CH₂— and CH₂-CH₂—) of diphenylmethane and diphenylethane ligands, has been found to occur in complexes 1–3 and 6.     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

2,4-二硫代尿嘧啶的紫外吸收光谱和共振拉曼光谱

硫代嘧啶碱基是光动力疗法潜在的重要光敏剂,其最低单重激发态的光物理研究已有广泛报道。然而,其较高激发态的跃迁性质和反应动力学研究较为稀少。因此,本文采用共振拉曼光谱和密度泛函理论计算方法研究2,4-二硫代尿嘧啶的紫外光谱和几个较高单重激发态的短时结构动力学。首先,基于共振拉曼光谱强度与电子吸收带振子强度f的关系,将紫外光谱去卷积成四个吸收带,分别为358 nm(f=0.0336)中等强度吸收带(A带),338 nm(f=0.1491)、301 nm(f=0.1795)和278 nm(f=0.3532)强而宽的吸收带(B、C和D带)。这一结果既吻合密度泛函理论计算结果,又符合共振拉曼光谱强度模式对紫外光谱带的预期。据此,去卷积得到的四个吸收带被分别指认为S0→S2跃迁、S0→S6跃迁、S0→S7跃迁和S_0→S_8跃迁。同时,分别对B,C和D带共振拉曼光谱进行了详细的指认,获得了短时动力学信息。结果表明,S_8态短时动力学的显著特征是在Franck-Condon区域或附近发生了S8(ππ~*)/S(nπ~*)势能面交叉引发的、伴随超快结构扭转的非绝热过程。S7和S6态短时动力学的主要特征是反应坐标的多维性,它们分别沿C_5C_6/C_2S_8/C_4S_(10)/N_2C_3+C_4N_3H_9/N_1C_2N_3/C_2N_1C_6/C_6N_1H_7/C_5C_6H_(12)和C_5C_6/N_3C_2/C_4S_(10)/C_2S_8+C_6N_1H_7/C_5C_6H_(12)/C_5C_6N_1/C_5C_6H_(12)/C_2N_1C_6/N_1C_2N_3/C_4N_3H_9/N_1C_2N_3等内坐标演化。     

PHTHALOCYANINE PHOTOSENSITIZATION OF MAMMALIAN CELLS: BIOCHEMICAL and ULTRASTRUCTURAL EFFECTS

Abstract— The concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺ and CI⁻ ions in the cytoplasm of octopus photoreceptor cells were determined before and after illumination by electron probe X-ray microanalysis. The concentrations of these elements in the dark-adapted photoreceptor cells were: Na⁺, 68.4; K⁺, 111.4; Ca²⁺, 4.0; Mg²⁺, 16.4; and CI⁻, 102.9 m M /kg of cytoplasm. Illumination raised the concentration of Na⁺ by 58 m M and that of Cl⁻ by 23 m M and reduced the K⁺ concentration by 47 m M /kg of cytoplasm. A trace increase of intracellular Ca²⁺ and a trace decrease of Mg²⁺ were observed. These results confirm the hypothesis that sodium ions flow in on illumination, and suggest the influx of chloride ions and the outflux of potassium ions during illumination. The intracellular concentrations of Na⁺, K⁺ and Cl⁺ can give the basis for calculating the ion permeability of ion channels in octopus photoreceptor cell membranes, using values of the membrane potentials obtained by electrophysiological studies     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–III. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE ANALOGS

The photodecomposition of sulfanilamide (4-aminobenzenesulfonamide), sulfacetamide. sulfathiazole. sulfadiazine, carbutamide and tolbutamide has been studied using the spin traps 2-methyl-2-nitrosopropanc and 5,5-dimethyl-l-pyrroline-l-oxide. The following radicals were trapped during the photolysis of sulfanilamide in aqueous solution: H' and HNC₆H₄SO₂NH, (α-fission). SO₂NH₂ and C₆H₄NH₂ (δ fission). H₂NC₆H₄SO₂ and NH₂ (δ-fission). Although the C.,H₄SO₂NH₂ and the SO; radicals were also detected these were not formed directly by homolytic bond fission. Homolytic bond fission was also observed during the irradiation of sulfacetamide (α.δ), sulfadiazine (α). carbutamide (α,δ) and tolbutamide (δ). All of the analogs, with the exception of tolbutamide, generated the SO; radical. Sulfacetamide, sulfadiazine and carbutamide generated the C₆H₄SO_2;NHR radical by some process that did not involve homolytic bond fission. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects.     

环型高分子链在良溶剂中的线团行为Ⅰ——r环～r线和f环～f线的理论推导及实验验证

本文用简单的数学关系导出了稀溶液中由同一种单体组成,分子量相同的环型和线型高分子线团的等效球体半径比r_环/r_线和摩擦因子比f_环/f_线均为1/([η]_线/[η]_环)^1/3.在不考虑排斥体积效应的情况下,这个比值为2^-1/3即0.7937.均方半径比为0.7937²≈0.63.     

THE PHOTOCHEMICAL INTERACTION BETWEEN THE TRIPLET STATE OF 8-METHOXYPSORALEN AND THE MELANIN PRECURSORL–3, 4 DIHYDROXYPHENYLALANINE

Abstract— The photochemical interaction between 8-methoxypsoralen (8-MOP) and the melanin precursorL–3,4-dihydroxyphenylalanine(dopaH₂) has been studied using laser flash photolysis. Triplet excited 8-MOP was thus found to abstract electrons from dopaH₂ ( k ∼ 2 × 10⁹ dm³ mol^-1 s^-1) to form semireduced 8-MOP and semioxidised dopaH₂.The technique of pulse radiolysis was used to establish separately the spectra of (a) the semi-reduced form of 8-MOP at pH 6.5 and (b) the semioxidised forms of dopaH₂ at pH 6.5, 5.8, 4.6 and 3.3. The corresponding λ_max and extinction coefficients found were: for 8-MOP at pH 6.5, λ_max= 350 nm (= 9050 dm³ mol^-1 cm^-1); for dopa at pH 6.5, λ_max= 305 nm (ε= 12000 dm³ mol^-1 cm^-1) and for dopaH at pH 3.3, λ= 305 nm (ε= 5900 dm³ mol^-1 cm^-1).     

SO_2和H_2O对CeO_2/TiO_2/堇青石催化剂选择催化还原NO_x性能的影响

采用浸渍法制备了以堇青石为基底、氧化铈为活性组分的整体式脱硝催化剂CeO2/TiO2/堇青石催化剂。通过与商业钒基催化剂(V2O5-WO3/TiO2/堇青石)的对比研究发现,CeO2/TiO2/堇青石催化剂表现出了优良的抗硫抗水性能,经过30 h抗硫抗水实验,CeO2/TiO2/堇青石催化剂的氮氧化物转化率仍能保持在70%以上,仅下降了5%。BET、XRD、FT-IR和TG表征结果表明,在含硫含水气氛中反应时,CeO2/TiO2/堇青石和V2O5-WO3/TiO2/堇青石催化剂表面均有硫酸铵盐的生成,且前者的生成量明显低于后者。NH3-DRIFT分析结果表明,在含硫含水气氛中两种催化剂表面Brnsted酸性都被增强,而Lewis酸性有所减弱。进一步的XPS分析结果表明,烟气中的SO2+H2O会使催化剂表面Ce4+向Ce3+发生转化,从而导致化学吸附氧含量增加,这是CeO2/TiO2/堇青石催化剂具有优良抗硫抗水性能的重要原因。