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1991 Volume 7 Issue 3
1991, 7(03): 257-259
doi: 10.3866/PKU.WHXB19910301
Abstract:
The Eigenequation is derived by the linear combination of unit orbitals approximation to calculate a protein entirely. The extended negative factor counting theorem is proved to solve above eigenequation. The concept of the "active orbitals" is introduced to analyse the calculated results. A series of insulins was calculated as the first application example of the theory and method.
The Eigenequation is derived by the linear combination of unit orbitals approximation to calculate a protein entirely. The extended negative factor counting theorem is proved to solve above eigenequation. The concept of the "active orbitals" is introduced to analyse the calculated results. A series of insulins was calculated as the first application example of the theory and method.
1991, 7(03): 260-269
doi: 10.3866/PKU.WHXB19910302
Abstract:
Using the UV absorption spectrometry in connection with computer simulation, the oxidation reaction kinetics of adrenaline forming adrenoehrome, with H_2O_2 in Cu(Ⅱ) existing as a catalyst had been studied. Since there is some overlap in the spectra of adrenaline and adrenochrome (Fig.1), the double wave-length method was used. The order of this reaction with respect to adrenaline is 1/2. The corresponding apparent reaction rate constants are independent of the initial concentration [Adin]_0 of adrenline (Table 1), but depend on the concentration of Cu(II), H_2O_2 and H~+ in accordance with equations (1~a) and (1~b). The experimental values kE and regression calculated values kC of the apparent rate constants k(app) under different experimental conditions are listed in the last two rows of Table 2, respectively. The linear correlation of kE and kC is shown in Fig.2. Examining this figure, it can be said that the regression calculated values are satisfiable.
In order to propose a reasonable probable mechanism of this reaction, by means of the electron paramagnetic resonance method, the radical intermidate was examined under the flow condition or sometimes a radical stabilizer...
Using the UV absorption spectrometry in connection with computer simulation, the oxidation reaction kinetics of adrenaline forming adrenoehrome, with H_2O_2 in Cu(Ⅱ) existing as a catalyst had been studied. Since there is some overlap in the spectra of adrenaline and adrenochrome (Fig.1), the double wave-length method was used. The order of this reaction with respect to adrenaline is 1/2. The corresponding apparent reaction rate constants are independent of the initial concentration [Adin]_0 of adrenline (Table 1), but depend on the concentration of Cu(II), H_2O_2 and H~+ in accordance with equations (1~a) and (1~b). The experimental values kE and regression calculated values kC of the apparent rate constants k(app) under different experimental conditions are listed in the last two rows of Table 2, respectively. The linear correlation of kE and kC is shown in Fig.2. Examining this figure, it can be said that the regression calculated values are satisfiable.
In order to propose a reasonable probable mechanism of this reaction, by means of the electron paramagnetic resonance method, the radical intermidate was examined under the flow condition or sometimes a radical stabilizer...
1991, 7(03): 270-275
doi: 10.3866/PKU.WHXB19910303
Abstract:
Ab initio molecular orbital calculations were performed on various structures of the acetaldehyde dimer at STO-3G and 6-31G levels. All the fully optimized structures of the dimer are cyclic structures with two C—H…O hydrogen bonds. At 6-31G level, the most stable geometry of the dimer is a symmetric one and the C—H…O hydrogen bonds are composed of hydrogen in—CHO group and carbonyl oxygen. The binding energy is —20.17 kJ·mol~(-1), which is in reasonable agreement with the estimated experimental value of -22.39±0.15 kJ·mol~(-1). The STO-3G basis set underestimates the binding energy and fails to give consistent description of the relative stabilities of various structures of the dimer with the 6-31G basis set.
Ab initio molecular orbital calculations were performed on various structures of the acetaldehyde dimer at STO-3G and 6-31G levels. All the fully optimized structures of the dimer are cyclic structures with two C—H…O hydrogen bonds. At 6-31G level, the most stable geometry of the dimer is a symmetric one and the C—H…O hydrogen bonds are composed of hydrogen in—CHO group and carbonyl oxygen. The binding energy is —20.17 kJ·mol~(-1), which is in reasonable agreement with the estimated experimental value of -22.39±0.15 kJ·mol~(-1). The STO-3G basis set underestimates the binding energy and fails to give consistent description of the relative stabilities of various structures of the dimer with the 6-31G basis set.
1991, 7(03): 276-280
doi: 10.3866/PKU.WHXB19910304
Abstract:
The protonation constant of the ligand and stability constants of its complexes with rare earths have been determined by poteatiometric titration at 25 ℃ and ionic strength μ=0.15 mol·L~(-1)(NaCl). The results indicate that rare earth elements can form 1:1 complexes with L-methionine. There is an apparent "tetrad effect" in this system. Shift of the yttrium position to the vicinity of Gd can be explained by the different polarization between the Ln~(3+) and the ligand. The enthalpy ehanges(△H_(101)) of the coordination reaction as represented by the reaction (M+L<=>ML) have been measured by calorimetric titration, where M and I denote rare earths and L-Met respectively. The ΔG_(101) and ΔS_(101) of these reaction have been calculated by using Gibbs' equation. Furthermore, the stability of rare earth complexes with L-Met has been compared with that of Cu~(2+), Zn~(2+), Fe~(2+), Fe~(3+) complexes with L-Met.
The protonation constant of the ligand and stability constants of its complexes with rare earths have been determined by poteatiometric titration at 25 ℃ and ionic strength μ=0.15 mol·L~(-1)(NaCl). The results indicate that rare earth elements can form 1:1 complexes with L-methionine. There is an apparent "tetrad effect" in this system. Shift of the yttrium position to the vicinity of Gd can be explained by the different polarization between the Ln~(3+) and the ligand. The enthalpy ehanges(△H_(101)) of the coordination reaction as represented by the reaction (M+L<=>ML) have been measured by calorimetric titration, where M and I denote rare earths and L-Met respectively. The ΔG_(101) and ΔS_(101) of these reaction have been calculated by using Gibbs' equation. Furthermore, the stability of rare earth complexes with L-Met has been compared with that of Cu~(2+), Zn~(2+), Fe~(2+), Fe~(3+) complexes with L-Met.
1991, 7(03): 281-288
doi: 10.3866/PKU.WHXB19910305
Abstract:
The product distribution and the rate constants of the transformation of cyclohexane, methylcyclohexane and methylcyclopentane over ZnZSM-5 and HZSM-5 have been studied by the pulse microreactor technigue. It is found that the aromatic distribution produced over these two catalysts are completely different. Over ZnZSM-5, the cyclohexane and methyleyclopentane are mainly converted to benzene, methylcyclohexane to toluene, showing a nearly complete dehydrogenation behavior, while the transformation of these cycloalkanes over HZSM-5 leads to yield a BTX mixture, indicating a typical consecutive reaction scheme, catalyzed by a monofunctional acid catalyst. These reactions are proved to be of the first order. Their apparent rate constants and activation energies were measured in the temperature range of 370~450 ℃.
For the aromatization of the methylcyclopentane, the transformation appears to proceed by methylcyclopentane isomerization to cyclohexane, followed by dehydrogenation. The kinetic data shows that the first step, i.e. isomerization, is much faster than the cyclohexane dehydrogenation.
The relative reaction rates over...
The product distribution and the rate constants of the transformation of cyclohexane, methylcyclohexane and methylcyclopentane over ZnZSM-5 and HZSM-5 have been studied by the pulse microreactor technigue. It is found that the aromatic distribution produced over these two catalysts are completely different. Over ZnZSM-5, the cyclohexane and methyleyclopentane are mainly converted to benzene, methylcyclohexane to toluene, showing a nearly complete dehydrogenation behavior, while the transformation of these cycloalkanes over HZSM-5 leads to yield a BTX mixture, indicating a typical consecutive reaction scheme, catalyzed by a monofunctional acid catalyst. These reactions are proved to be of the first order. Their apparent rate constants and activation energies were measured in the temperature range of 370~450 ℃.
For the aromatization of the methylcyclopentane, the transformation appears to proceed by methylcyclopentane isomerization to cyclohexane, followed by dehydrogenation. The kinetic data shows that the first step, i.e. isomerization, is much faster than the cyclohexane dehydrogenation.
The relative reaction rates over...
1991, 7(03): 289-293
doi: 10.3866/PKU.WHXB19910306
Abstract:
Pyrene was used as a spectral probe in studying the interaction of some watersoluble aliphatic alcohols with β-cyclodextrin (β-CD) by fluorescence and absorption spectroseopies. Results showed that monobasic alcohol can decrease the micropolarity of β-CD cavity, but the formation constant of pyrene-β-CD inclusion complex is being larger, and polybasie alcohol had the opposite effects. The hydrogen-bonding interaction between alcohols and β-CD was proposed to explain the results.
Pyrene was used as a spectral probe in studying the interaction of some watersoluble aliphatic alcohols with β-cyclodextrin (β-CD) by fluorescence and absorption spectroseopies. Results showed that monobasic alcohol can decrease the micropolarity of β-CD cavity, but the formation constant of pyrene-β-CD inclusion complex is being larger, and polybasie alcohol had the opposite effects. The hydrogen-bonding interaction between alcohols and β-CD was proposed to explain the results.
1991, 7(03): 294-299
doi: 10.3866/PKU.WHXB19910307
Abstract:
In this paper, two kinds of appropriate cluster model Fe_5S and Fe_9S are chosen for the chemisorption system of C(2×2)S/Fe(001), The electronic structure of these two clusters, the characterics of chemisorption bonding and the picture of adsorption interaction were sutdied using SCF-X_α-MS method. Results show that adsorption of sulfur on Fe(001) single crystal surface has strong Iocal effect and sulfer 3P_x, 3P_y orbitals hybridize with the first layer iron 3d_(xz), 3d_(yz), and sulfur, 3P_z may interact with a second layer iron 4s and 3d_z2. The optimized chemisorption geomtries are in fair agreement with ARPEFS result of C(2×2)S/Fe(001) by X.S.Zhang et al.
In this paper, two kinds of appropriate cluster model Fe_5S and Fe_9S are chosen for the chemisorption system of C(2×2)S/Fe(001), The electronic structure of these two clusters, the characterics of chemisorption bonding and the picture of adsorption interaction were sutdied using SCF-X_α-MS method. Results show that adsorption of sulfur on Fe(001) single crystal surface has strong Iocal effect and sulfer 3P_x, 3P_y orbitals hybridize with the first layer iron 3d_(xz), 3d_(yz), and sulfur, 3P_z may interact with a second layer iron 4s and 3d_z2. The optimized chemisorption geomtries are in fair agreement with ARPEFS result of C(2×2)S/Fe(001) by X.S.Zhang et al.
1991, 7(03): 300-304
doi: 10.3866/PKU.WHXB19910308
Abstract:
The SERRS spectra of sodium fluorescein at various pH values adsorbed on silverisland film are presented. Due to the fact that sodium fluorescein exists in different ionic forms in the solutions at different pH values, these SERRS spectra are different. The difference lies not in the freciuency, but in the intensity of Raman bands. The intensity variation of the band with the pH value falls into two categeries depending on the nature of corresponding modes of vibration. The experimental results are interpred by using a "four-level model" with the theory of resonance Raman scttering.
The SERRS spectra of sodium fluorescein at various pH values adsorbed on silverisland film are presented. Due to the fact that sodium fluorescein exists in different ionic forms in the solutions at different pH values, these SERRS spectra are different. The difference lies not in the freciuency, but in the intensity of Raman bands. The intensity variation of the band with the pH value falls into two categeries depending on the nature of corresponding modes of vibration. The experimental results are interpred by using a "four-level model" with the theory of resonance Raman scttering.
1991, 7(03): 305-310
doi: 10.3866/PKU.WHXB19910309
Abstract:
Variations of the elemental concentration of the YBCO films prepared by MOD method, diffusion and interactions between the films and ZrO_2 substrate have been studied by means of angular dependent XPS technique. A drastic change in the stoichiometry of YBCO films in surface region at different heating steps have been observed. For example, Cu~(2+)-enrichment and Ba~(2+)-deficiency occur in surface region for both thin (～0.1 μm) and thick (1～1.5 μm) films after heating the samples at about 530°～720 ℃. However, above 800 ℃ Cu~(2+)-deficiency is observed clearly, and the higher the temperature, the more the Cu~(2+)-deficiency. In addition, the extent of interdiffusion and interaction also increases with increasing temperature. After heating at 800 ℃ diffusion of Ba~(2+) From the thin film into ZrO_2 substrate is detected, and the valence of copper is +2. Whereas, with a heating temperature of 950 ℃, a Ba~(2+)-rich layer on the substrate has been formed, and the valence of copper on the layer is mainly +1. The results also show that degradation of the superconducting property caused by the diffusion and interaction is more severe for the thin film than for thick film.
Variations of the elemental concentration of the YBCO films prepared by MOD method, diffusion and interactions between the films and ZrO_2 substrate have been studied by means of angular dependent XPS technique. A drastic change in the stoichiometry of YBCO films in surface region at different heating steps have been observed. For example, Cu~(2+)-enrichment and Ba~(2+)-deficiency occur in surface region for both thin (～0.1 μm) and thick (1～1.5 μm) films after heating the samples at about 530°～720 ℃. However, above 800 ℃ Cu~(2+)-deficiency is observed clearly, and the higher the temperature, the more the Cu~(2+)-deficiency. In addition, the extent of interdiffusion and interaction also increases with increasing temperature. After heating at 800 ℃ diffusion of Ba~(2+) From the thin film into ZrO_2 substrate is detected, and the valence of copper is +2. Whereas, with a heating temperature of 950 ℃, a Ba~(2+)-rich layer on the substrate has been formed, and the valence of copper on the layer is mainly +1. The results also show that degradation of the superconducting property caused by the diffusion and interaction is more severe for the thin film than for thick film.
1991, 7(03): 311-317
doi: 10.3866/PKU.WHXB19910310
Abstract:
The salt effect coefficients (k_s) of nonelectrolyte solute dissoving in nonaqueous electrolyte solutions, which is composed of salt (NaI,or KI) and sulfolane, was calculated by the scale particle theory. Considering the distribution behavior of the particles in solution and the forms of molecular interactions,we calculated K_s in different ways. 1. The term of hard sphere interaction (k_α) was calculated by Masterton -Lee's equation. The term of soft sphere interaction (k_β) was treated by Y. Hu's radial distribution funtion method, ie take the first coordination circle as in-order, and out of the circle as random mixing. Fur-thermore, we take the following interaction form into calculation: dipole-dipole, dipole-induced dipole, dipole-charge of ion and charge-induced dipole. The results shown that the treatment method used is better than others. 2. The molecular hard sphere diametere σ and energy parameter ∈/k were obtained from various empirical equations. These equations contain some parameters which can be t easily. By comparing the calculated k_s with the experimental results, when σ_2=0.563 nm and ion's diameter is in electronic density scale, the agreement between theory and experimental result is od.
The salt effect coefficients (k_s) of nonelectrolyte solute dissoving in nonaqueous electrolyte solutions, which is composed of salt (NaI,or KI) and sulfolane, was calculated by the scale particle theory. Considering the distribution behavior of the particles in solution and the forms of molecular interactions,we calculated K_s in different ways. 1. The term of hard sphere interaction (k_α) was calculated by Masterton -Lee's equation. The term of soft sphere interaction (k_β) was treated by Y. Hu's radial distribution funtion method, ie take the first coordination circle as in-order, and out of the circle as random mixing. Fur-thermore, we take the following interaction form into calculation: dipole-dipole, dipole-induced dipole, dipole-charge of ion and charge-induced dipole. The results shown that the treatment method used is better than others. 2. The molecular hard sphere diametere σ and energy parameter ∈/k were obtained from various empirical equations. These equations contain some parameters which can be t easily. By comparing the calculated k_s with the experimental results, when σ_2=0.563 nm and ion's diameter is in electronic density scale, the agreement between theory and experimental result is od.
1991, 7(03): 318-322
doi: 10.3866/PKU.WHXB19910311
Abstract:
In DMF-H_2O(35%DMF, V/V) solution,the interaction between an anionic cyanine dye, 3,3'-di-(γ-sulfoProPyl)-9-ethyl-4, 5,4', 5'-dinaphthothis-carbocyanine triethylamine salt (Ⅰ) and its counterions, which induced J-aggregate formation, was studied by calorimetric and counterion activity measurement method. From calorimetric diagram,it was found,when CdCl_2 and LaCl_3 were added,J-aggregation enthalpy, △H_s, were -42.6, -42.0 kJ·mol~(-1) and the ratios of bounded counterions to the dye (Ⅰ) J-aggregate were 0.48:1, 0.31:1, respectively. It was also obtained from counterion activety measurement that the ratio of bounded Cd~(2+) to dye II) J-aggregase was 0.47:1. Such results indicated that dye (I) and counterions had formed a salt-like totality in the J-aggregate.
In DMF-H_2O(35%DMF, V/V) solution,the interaction between an anionic cyanine dye, 3,3'-di-(γ-sulfoProPyl)-9-ethyl-4, 5,4', 5'-dinaphthothis-carbocyanine triethylamine salt (Ⅰ) and its counterions, which induced J-aggregate formation, was studied by calorimetric and counterion activity measurement method. From calorimetric diagram,it was found,when CdCl_2 and LaCl_3 were added,J-aggregation enthalpy, △H_s, were -42.6, -42.0 kJ·mol~(-1) and the ratios of bounded counterions to the dye (Ⅰ) J-aggregate were 0.48:1, 0.31:1, respectively. It was also obtained from counterion activety measurement that the ratio of bounded Cd~(2+) to dye II) J-aggregase was 0.47:1. Such results indicated that dye (I) and counterions had formed a salt-like totality in the J-aggregate.
1991, 7(03): 323-328
doi: 10.3866/PKU.WHXB19910312
Abstract:
In the study on the model of the active site of superoxide dismutase, some hicopper (Ⅱ) maerocyclic complexes have been synthesized. This paper discribes the synthesis and crystal structure of a new μ-thiocyanato-complex. The crystal belongs to monoclinic space group P2/n with a=1.6274(8), b=0.8110(3), c=2.3199(10) nm, β=98.46(4)°, V=3.030 nm, Z=4, D_c=1.57 g·cm~(-3). The crystal structure was solved by direct method and difference Fourier synthesis. The refinement with anisotropic temperature factors for non-hydrogen atoms gave the final discrepancy factor R=0.088 for 1945 reflections.
The macrocycles are at the symmetric center of the cell. Both coppers are in a distorted square-pyramidal environment. The two copper ions in the same macrocycle are noninteracting (Cu-Cu=0.5478 nm). The copper ions in the different macrocycles are bridged by thiocyanate to form a infinite chain in the crystal. The bassal positions of the pyramid consist of three nitrogen atoms of the diethylenetriamine fragment of the vertex of the distorted square-pyramid is nitrogen or sulfur atom of the bridged thiocyanate. The distance of two copper ions bridged by thiocyanate is 0.6695 nm. The interaction of copper with the vertical nitrogen atom (Cu-N=0.2315 nm) is stronger than with vertical sulfur atom (Cu-S=0.2824 nm).
In the study on the model of the active site of superoxide dismutase, some hicopper (Ⅱ) maerocyclic complexes have been synthesized. This paper discribes the synthesis and crystal structure of a new μ-thiocyanato-complex. The crystal belongs to monoclinic space group P2/n with a=1.6274(8), b=0.8110(3), c=2.3199(10) nm, β=98.46(4)°, V=3.030 nm, Z=4, D_c=1.57 g·cm~(-3). The crystal structure was solved by direct method and difference Fourier synthesis. The refinement with anisotropic temperature factors for non-hydrogen atoms gave the final discrepancy factor R=0.088 for 1945 reflections.
The macrocycles are at the symmetric center of the cell. Both coppers are in a distorted square-pyramidal environment. The two copper ions in the same macrocycle are noninteracting (Cu-Cu=0.5478 nm). The copper ions in the different macrocycles are bridged by thiocyanate to form a infinite chain in the crystal. The bassal positions of the pyramid consist of three nitrogen atoms of the diethylenetriamine fragment of the vertex of the distorted square-pyramid is nitrogen or sulfur atom of the bridged thiocyanate. The distance of two copper ions bridged by thiocyanate is 0.6695 nm. The interaction of copper with the vertical nitrogen atom (Cu-N=0.2315 nm) is stronger than with vertical sulfur atom (Cu-S=0.2824 nm).
1991, 7(03): 329-332
doi: 10.3866/PKU.WHXB19910313
Abstract:
The phase transition of 400% sodium dodecyl sulfate (SDS)/water system has been studied by employing pyrene as a fluorescent probe in the temperature range of -20 ℃—+30 ℃. The binary system mainly under es coagel-liquid crystal phase transition at about 20 ℃. Free water layer melts at 0 ℃, below and above that different coagel phases were found. Anoval coagel phase was brought forth after annealing at -17 ℃ for 12 hours. All these phases have been fairly characterized by I_E/I_M. Structurual aspects of these phases are idscussed concerning with the fluorescence information.
The phase transition of 400% sodium dodecyl sulfate (SDS)/water system has been studied by employing pyrene as a fluorescent probe in the temperature range of -20 ℃—+30 ℃. The binary system mainly under es coagel-liquid crystal phase transition at about 20 ℃. Free water layer melts at 0 ℃, below and above that different coagel phases were found. Anoval coagel phase was brought forth after annealing at -17 ℃ for 12 hours. All these phases have been fairly characterized by I_E/I_M. Structurual aspects of these phases are idscussed concerning with the fluorescence information.
1991, 7(03): 333-336
doi: 10.3866/PKU.WHXB19910314
Abstract:
The molecular structures and chemical bonds of CX_3NO_2 (X=F,Cl) have been studied by ab initio method at STO-3G level, full optimized. The results indicate that eclipsed structure and staggered structure have similar energy and similar stability for each molecule, they can co-exist in gas phase. Ab initio results are in agreement with experimental results.
The molecular structures and chemical bonds of CX_3NO_2 (X=F,Cl) have been studied by ab initio method at STO-3G level, full optimized. The results indicate that eclipsed structure and staggered structure have similar energy and similar stability for each molecule, they can co-exist in gas phase. Ab initio results are in agreement with experimental results.
1991, 7(03): 337-341
doi: 10.3866/PKU.WHXB19910315
Abstract:
1991, 7(03): 342-344
doi: 10.3866/PKU.WHXB19910316
Abstract:
A potential energy function has been derived for 10 excited states of NO~+, which can be represented as
V(r)=-D_e(1-(1+a(r))exp(γ(r))W(r)+D_e+△T_e
The cubic force constants evaluated from this function, are in agreement with the spectroscopic data. Therefore, this simple function can be successfully used for most of the excited states for NO~+.
A potential energy function has been derived for 10 excited states of NO~+, which can be represented as
V(r)=-D_e(1-(1+a(r))exp(γ(r))W(r)+D_e+△T_e
The cubic force constants evaluated from this function, are in agreement with the spectroscopic data. Therefore, this simple function can be successfully used for most of the excited states for NO~+.
1991, 7(03): 345-348
doi: 10.3866/PKU.WHXB19910317
Abstract:
The concentration (c)-voltage (V) relations of K~+ and Ca~(2+) in surfactant solutions have been measured by ionic selective electrodes. The results show that it is very easy to form ion-pair, for alkyl sulfate(RS)and metallic cations which is the reason why the eletrolyte tolerance of RS is very low; The situation between the polyoxyethylene group in alkylpolyox yethylene ether sulfate salts (RE_nS) and multivalent metallic cations (Mn~(n+)) may be considered as the interaction performed by complexation, which prevents RE_nS and M~(n+) to form ion-pair, and this is one of the reasons why RE_nS have a higher eletrolyte tolerance.
The concentration (c)-voltage (V) relations of K~+ and Ca~(2+) in surfactant solutions have been measured by ionic selective electrodes. The results show that it is very easy to form ion-pair, for alkyl sulfate(RS)and metallic cations which is the reason why the eletrolyte tolerance of RS is very low; The situation between the polyoxyethylene group in alkylpolyox yethylene ether sulfate salts (RE_nS) and multivalent metallic cations (Mn~(n+)) may be considered as the interaction performed by complexation, which prevents RE_nS and M~(n+) to form ion-pair, and this is one of the reasons why RE_nS have a higher eletrolyte tolerance.
1991, 7(03): 349-353
doi: 10.3866/PKU.WHXB19910318
Abstract:
The influence of surface-adsorbed NO_2 on the surface photovoltaic properties of MnPc and the related charge transfer interaction were studied by surface photovoltage spectroscopy. In comparison with other metal-phthalocyanines, the photovoltaic response of MnPc is very particular. A strong photovoltaic response band near 510 nm was observed besides B band (365 nm) and Q bands (640, 725 nm), which was assigned as the MLCT transition from the e_g(d_(xz), d_(yz)) orbital of central manganese ion to the b_(lu)(π~*) orbital of Pc ring. Under given conditions, the MnPc exhibited reverse photovoltaic response after adsorbing NO_2 and, consequently, the spectral distribution changed remarkably, which suggests that there is a strong charge transfer interaction between them. The photodesorption experiments indicated that NO_2 was adsorbed by the atomic oxygen bridged dimer of MnPc prior to the MnPc monomer and made the dimer partly decomposed. Besides, there is a selective interaction between NO_2 and MnPc with respect to the various electron transitions of MnPc.
The influence of surface-adsorbed NO_2 on the surface photovoltaic properties of MnPc and the related charge transfer interaction were studied by surface photovoltage spectroscopy. In comparison with other metal-phthalocyanines, the photovoltaic response of MnPc is very particular. A strong photovoltaic response band near 510 nm was observed besides B band (365 nm) and Q bands (640, 725 nm), which was assigned as the MLCT transition from the e_g(d_(xz), d_(yz)) orbital of central manganese ion to the b_(lu)(π~*) orbital of Pc ring. Under given conditions, the MnPc exhibited reverse photovoltaic response after adsorbing NO_2 and, consequently, the spectral distribution changed remarkably, which suggests that there is a strong charge transfer interaction between them. The photodesorption experiments indicated that NO_2 was adsorbed by the atomic oxygen bridged dimer of MnPc prior to the MnPc monomer and made the dimer partly decomposed. Besides, there is a selective interaction between NO_2 and MnPc with respect to the various electron transitions of MnPc.
1991, 7(03): 354-357
doi: 10.3866/PKU.WHXB19910319
Abstract:
The cathodic reduction of SbO~+ ions in sodium sulphate solution at pH 4.0 has been investigated using potentiodynamic polarization at rotating disc electrode (RDE), rotating ring disc electrode(RRDE) and AC impedance techniques. Results show that SbO~+ ions can be eventually reduced to stibine SbH_3 through a 6-electron process, whose formation is confirmed by RRDE experiments. The reduction is diffusioncontrolled at potentials negative to -1.28 V. The values of the diffusion coefficient of SbO~+ ions calculated on the basis of the experimental results for 3-electron and 6-electron reduction are very consistent; they are (1.45±0.15)×10~(-6) cm~2·s~(-1) and (1.47±0.15)×10~(-6) cm~2·s~(-1), respectively.
The cathodic reduction of SbO~+ ions in sodium sulphate solution at pH 4.0 has been investigated using potentiodynamic polarization at rotating disc electrode (RDE), rotating ring disc electrode(RRDE) and AC impedance techniques. Results show that SbO~+ ions can be eventually reduced to stibine SbH_3 through a 6-electron process, whose formation is confirmed by RRDE experiments. The reduction is diffusioncontrolled at potentials negative to -1.28 V. The values of the diffusion coefficient of SbO~+ ions calculated on the basis of the experimental results for 3-electron and 6-electron reduction are very consistent; they are (1.45±0.15)×10~(-6) cm~2·s~(-1) and (1.47±0.15)×10~(-6) cm~2·s~(-1), respectively.
1991, 7(03): 358-361
doi: 10.3866/PKU.WHXB19910320
Abstract:
The reaction of 1,2-dichloroethane and chlorine redical was studied. Chlorine radical was produced by photolysis of chlorine gas using nitrogen laser.
Quantum yield of this reaction is much higher than that of the reaction without chlorine. The mechanism of this reaction has been discussed.
The reaction of 1,2-dichloroethane and chlorine redical was studied. Chlorine radical was produced by photolysis of chlorine gas using nitrogen laser.
Quantum yield of this reaction is much higher than that of the reaction without chlorine. The mechanism of this reaction has been discussed.
1991, 7(03): 362-365
doi: 10.3866/PKU.WHXB19910321
Abstract:
In this paper a rare earth-HEDTA-serine (Ser) ternary system has been studied by potentiometric titration at 25 ℃ with an ionic strength of 0.15 mol·L~(-1)(NaCl). The excitation and fluorescence spectra of TbCl_3, Tb-Ser,Tb-HEDTA and Tb-HEDTA-Ser have been determined at room temperature. The stability constants of these ternary complexes have been obtained. It has been found that Tb-HEDTA-Ser ternary system exhibit scharacteristic fluorescence spectrum of Tb~(3+) sensitized by two ligands. The results mean that the chemical bond tetween the central ion and the ligand in this ternary system is predominantly ionic in character, and the energy transfer from ligand to Tb~(3+) is performed by a kind of short-range electron exchange action.
In this paper a rare earth-HEDTA-serine (Ser) ternary system has been studied by potentiometric titration at 25 ℃ with an ionic strength of 0.15 mol·L~(-1)(NaCl). The excitation and fluorescence spectra of TbCl_3, Tb-Ser,Tb-HEDTA and Tb-HEDTA-Ser have been determined at room temperature. The stability constants of these ternary complexes have been obtained. It has been found that Tb-HEDTA-Ser ternary system exhibit scharacteristic fluorescence spectrum of Tb~(3+) sensitized by two ligands. The results mean that the chemical bond tetween the central ion and the ligand in this ternary system is predominantly ionic in character, and the energy transfer from ligand to Tb~(3+) is performed by a kind of short-range electron exchange action.
1991, 7(03): 366-370
doi: 10.3866/PKU.WHXB19910322
Abstract:
The photoelectrochemical behavior of the passive film on iron in pH=8.4 borate buffer solution was investigated. The mechanism considered for the generation of the photocurrent in the passive film, and the principle of the measurement of photocurrent were discussed. The band model of noncrytalline semiconductor was used to demonstrate the depedence of photocurrent on electrode potential and light wavelength. Results indicate that the passive film formed on iron in pH=8.4 borate solution is a noncrystalline semiconductor, its flatband potential (φ_(fb)) is -0.30 V(SCE), band gap energy (E_g) is affected by measuring potential (φ_m), When +0.30 V<φ_m<+0.80 V (SCE), E_g is 1.9 eV.
The photoelectrochemical behavior of the passive film on iron in pH=8.4 borate buffer solution was investigated. The mechanism considered for the generation of the photocurrent in the passive film, and the principle of the measurement of photocurrent were discussed. The band model of noncrytalline semiconductor was used to demonstrate the depedence of photocurrent on electrode potential and light wavelength. Results indicate that the passive film formed on iron in pH=8.4 borate solution is a noncrystalline semiconductor, its flatband potential (φ_(fb)) is -0.30 V(SCE), band gap energy (E_g) is affected by measuring potential (φ_m), When +0.30 V<φ_m<+0.80 V (SCE), E_g is 1.9 eV.
1991, 7(03): 371-374
doi: 10.3866/PKU.WHXB19910323
Abstract:
Binding energies of Ln 3d_(5/2) of Rare Earths and N_(1S), O_(1S) of ligands in two series of lanthanide complexes of RE(NO_3)_3·C_(12)H_(22)O_4 and Ln(NO_3)_3·2H_2O·bipy·B-15-C-5 have been measured. Shake down satellite peaks for lanthanide ions have also been detected. The character of coordination bonds is discussed based on the satellite phenomena.
Binding energies of Ln 3d_(5/2) of Rare Earths and N_(1S), O_(1S) of ligands in two series of lanthanide complexes of RE(NO_3)_3·C_(12)H_(22)O_4 and Ln(NO_3)_3·2H_2O·bipy·B-15-C-5 have been measured. Shake down satellite peaks for lanthanide ions have also been detected. The character of coordination bonds is discussed based on the satellite phenomena.
1991, 7(03): 375-378
doi: 10.3866/PKU.WHXB19910324
Abstract:
Te 100 ml of 6<PH≤13 < PVA. by protected is colloid hydroxide ferric the and stable very be to aqqears solution transparent brown reddish Therefore, other. each on interact water of body faced PVA hydroxy hydrophilic but interior, toward has framework carbon chain main this when hydroxide, maion between force Waals der van aid with hydrophobic included bridge hydroxylic multi-nucleate say that time, formed substance inclusion tubular a Then solution. aqueous basic above added ion PVA, polymer linear region spiral in speedily fills it formed, The follows. as deduced emerging new speciels for process formation spectrum, visible violet ultra ESR, IR, XPS, its studied cause formed. FeCl_3·6H_2O, 0.1grams 1~5% contained>
1991, 7(03): 379-384
doi: 10.3866/PKU.WHXB19910325
Abstract:
