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1987 Volume 3 Issue 1
1987, 3(01): 1-3
doi: 10.3866/PKU.WHXB19870101
Abstract:
Electrodes were prepared with heating commercial pure iron chips buried in M powder and showe dboth n-and p-type photoresponses.The photoresponses were so weak that in fact they were totally buried inthe noise.Hence asignal averager was used. After 1000 cycles'summation the signal to noise ratio was greatly improved and we obtained a wave form series showing the conversion of n-type, p-type photoresponses for the first time.
Fig.1(a): E=0.261V. The absolute peak-to-peak photovoltagevalue (ΔV_(ph)) equals 13.4 mV and shows a typical n-type photoresponse. (b); E=-0.04 V, ΔV_(ph)=1.24 mV, still an -n-type response, but when light is chopped off, the electrode potential reaches its stable value much faster than in (a). (c): When E=-0.076 V, which is only 0.036 V more negative than in (b), in the latter 85% part of illuminating period, electrode potential tends to increase, demonstrating some p-type character. (d): As E=-0.09 V, the magnitude of p-type response almost equals that of n-type. (e): As E=-0.12 V, the main response belongs to p-type, and ΔV_(ph) is only 0.634 mV. This electrode potential is much more positive than the flat band potential of the undoped iron oxide electrode (E_(fb) is about -0.5 V). (f): E=-0.17 V. There is still a small n-type response at the beginning of every illuminating period, and the whole curve appears to be p-type responnse. (g): E=-0.36 V. Typical p-type response appears. ΔV_(ph)=2.05 mV. (h) and (i): E=-0.40 V and -0.45 V. ΔV_(ph) drop to 1.55 mV and 1.05 mV respectively. the above data were reproducible, no retardation of photoresponse was observed when potential was changed.
An XPS surface analysis was performed thereafter on the same electrode. A peak of Mg1S at 1305 eV(BE) is apparent. Huge amount of Mg exists on the surface layer. the relative atomic concentration (s compared with Fe) reaches 15-20 AT%. After Ar~+ etching, the amount of Mg decreases. Fig.2 is the result after 9 minutes′ Ar~+ etching. A possible explanation of these experimental facts based on model of energy band of semiconductors was given.
Electrodes were prepared with heating commercial pure iron chips buried in M powder and showe dboth n-and p-type photoresponses.The photoresponses were so weak that in fact they were totally buried inthe noise.Hence asignal averager was used. After 1000 cycles'summation the signal to noise ratio was greatly improved and we obtained a wave form series showing the conversion of n-type, p-type photoresponses for the first time.
Fig.1(a): E=0.261V. The absolute peak-to-peak photovoltagevalue (ΔV_(ph)) equals 13.4 mV and shows a typical n-type photoresponse. (b); E=-0.04 V, ΔV_(ph)=1.24 mV, still an -n-type response, but when light is chopped off, the electrode potential reaches its stable value much faster than in (a). (c): When E=-0.076 V, which is only 0.036 V more negative than in (b), in the latter 85% part of illuminating period, electrode potential tends to increase, demonstrating some p-type character. (d): As E=-0.09 V, the magnitude of p-type response almost equals that of n-type. (e): As E=-0.12 V, the main response belongs to p-type, and ΔV_(ph) is only 0.634 mV. This electrode potential is much more positive than the flat band potential of the undoped iron oxide electrode (E_(fb) is about -0.5 V). (f): E=-0.17 V. There is still a small n-type response at the beginning of every illuminating period, and the whole curve appears to be p-type responnse. (g): E=-0.36 V. Typical p-type response appears. ΔV_(ph)=2.05 mV. (h) and (i): E=-0.40 V and -0.45 V. ΔV_(ph) drop to 1.55 mV and 1.05 mV respectively. the above data were reproducible, no retardation of photoresponse was observed when potential was changed.
An XPS surface analysis was performed thereafter on the same electrode. A peak of Mg1S at 1305 eV(BE) is apparent. Huge amount of Mg exists on the surface layer. the relative atomic concentration (s compared with Fe) reaches 15-20 AT%. After Ar~+ etching, the amount of Mg decreases. Fig.2 is the result after 9 minutes′ Ar~+ etching. A possible explanation of these experimental facts based on model of energy band of semiconductors was given.
1987, 3(01): 4-10
doi: 10.3866/PKU.WHXB19870102
Abstract:
There is no symmetry throughout the reaction process of [1, n] sigmatropic rearrangements except in the transition state, in which the suprafacial process is of C symmetry, while the antarafacial one is C_2 (Fig.1).The accidental degeneracy at the crossing of the FMOs in the forbidden [1, n] sigmatropic rearrangenents, where n is an odd number, has been explained by two different concepts, i.e., by symmetry and by alternance. There are indeed a symmetrical NBMO and an antisymmetrical NBMO in the transition state. According to the theory of alternance and the degenerate perturbation theory, they shoule be linearly combined into MOs keeping continuity with the earlier and the later states, the resulting MOs being thus unsymmetrical (cf. Table 1). Therefore, the accidental degeneracy cannot be explained by the concept of symmetry, and the correct explanation should be concerned with the alternance as in the previous paper~[5]. The selection rules for [1, n] sigmatropic rearrangements with an odd number of n can readily be deduced by the theory of alternance, but not by symmetry.
There is no symmetry throughout the reaction process of [1, n] sigmatropic rearrangements except in the transition state, in which the suprafacial process is of C symmetry, while the antarafacial one is C_2 (Fig.1).The accidental degeneracy at the crossing of the FMOs in the forbidden [1, n] sigmatropic rearrangenents, where n is an odd number, has been explained by two different concepts, i.e., by symmetry and by alternance. There are indeed a symmetrical NBMO and an antisymmetrical NBMO in the transition state. According to the theory of alternance and the degenerate perturbation theory, they shoule be linearly combined into MOs keeping continuity with the earlier and the later states, the resulting MOs being thus unsymmetrical (cf. Table 1). Therefore, the accidental degeneracy cannot be explained by the concept of symmetry, and the correct explanation should be concerned with the alternance as in the previous paper~[5]. The selection rules for [1, n] sigmatropic rearrangements with an odd number of n can readily be deduced by the theory of alternance, but not by symmetry.
1987, 3(01): 11-15
doi: 10.3866/PKU.WHXB19870103
Abstract:
Thermodynamic properties of the complexation of 18-crown-6 with KCI, KBr, KI, KClO_4, KNO_3, KBrO_3,K_2CO_3 and K_2S_2O_8 in water solution were studied at 25 ℃ by calorimetric titration. The stability constants of coordination compounds and enthalpies of coordination were calculated directly.It was shown that among the calculated volues the stability constants of coordination compounds formed by 18-crown-6 with KNO_3 and K_2S_2O_8 were the highest.
The influence of anions on the stability of coordination compounds may be that:(1) The concomitant anions have effection the ligand conformation, which will cause considerable changes in the entropy of complexation and the enthalpy of complexation; (2) The strength of bonding force of anion-K~+ effects the strength of ion-dipole bond of K~+-ligand; (3) The hydration of anion itself also effects the complexation of K~+ with crown ether.
The sequence of the stability constants of coordination compounds of 18-crown-6 with the 8 potassium salts is S_2O_8~(2-)>NO_3~->CO_3~(2-)>Br~->Cl~->I~->ClO_4~->BrO_3~-. The order of salts in the complexation enthalpy sequence is, however, different.
Thermodynamic properties of the complexation of 18-crown-6 with KCI, KBr, KI, KClO_4, KNO_3, KBrO_3,K_2CO_3 and K_2S_2O_8 in water solution were studied at 25 ℃ by calorimetric titration. The stability constants of coordination compounds and enthalpies of coordination were calculated directly.It was shown that among the calculated volues the stability constants of coordination compounds formed by 18-crown-6 with KNO_3 and K_2S_2O_8 were the highest.
The influence of anions on the stability of coordination compounds may be that:(1) The concomitant anions have effection the ligand conformation, which will cause considerable changes in the entropy of complexation and the enthalpy of complexation; (2) The strength of bonding force of anion-K~+ effects the strength of ion-dipole bond of K~+-ligand; (3) The hydration of anion itself also effects the complexation of K~+ with crown ether.
The sequence of the stability constants of coordination compounds of 18-crown-6 with the 8 potassium salts is S_2O_8~(2-)>NO_3~->CO_3~(2-)>Br~->Cl~->I~->ClO_4~->BrO_3~-. The order of salts in the complexation enthalpy sequence is, however, different.
1987, 3(01): 16-21
doi: 10.3866/PKU.WHXB19870104
Abstract:
A model LEPS potential and a pseudo crystal approximation have been used to describe the interaction of O_2 with Ag-Au(110)face. The potential energy surfaces of oxygen on alloys with ld contents of 0, 0.15, 0.30, 0.45, 0.60, 0.80 have been investigated. Both the heights of the potential energy barrier and the heats of dissociative adsorption of oxygen increase with ld contents. The potential energy surfaces with ld contents of 0, 0.15, 0.30 exhibit a local minimum correspon- ding to molecular adsorption.
A model LEPS potential and a pseudo crystal approximation have been used to describe the interaction of O_2 with Ag-Au(110)face. The potential energy surfaces of oxygen on alloys with ld contents of 0, 0.15, 0.30, 0.45, 0.60, 0.80 have been investigated. Both the heights of the potential energy barrier and the heats of dissociative adsorption of oxygen increase with ld contents. The potential energy surfaces with ld contents of 0, 0.15, 0.30 exhibit a local minimum correspon- ding to molecular adsorption.
1987, 3(01): 22-29
doi: 10.3866/PKU.WHXB19870105
Abstract:
On the theoretical basis of thermokinetics proposed in reference, a for- mula for the method of dimesionless parameters for second order reactions with equal concentrations was derived. The values of relevant functions of dimesionless parameters were calculated. The properties of the function were discussed. And a functional table needed for calculating the rate constants of reaction was listed.
This method was then used to study the saponification of ethyl benzoate in “50%” aqueous alcohol solvent at 25.0 ℃ and 40.0 ℃. The thermographic cuve of this reactions was recorded. The rate constants of this reaction calculated with this method are in agreement with values in the literature.
Thus, the validity of this method and its theoretical basis should be proved.
On the theoretical basis of thermokinetics proposed in reference, a for- mula for the method of dimesionless parameters for second order reactions with equal concentrations was derived. The values of relevant functions of dimesionless parameters were calculated. The properties of the function were discussed. And a functional table needed for calculating the rate constants of reaction was listed.
This method was then used to study the saponification of ethyl benzoate in “50%” aqueous alcohol solvent at 25.0 ℃ and 40.0 ℃. The thermographic cuve of this reactions was recorded. The rate constants of this reaction calculated with this method are in agreement with values in the literature.
Thus, the validity of this method and its theoretical basis should be proved.
1987, 3(01): 30-34
doi: 10.3866/PKU.WHXB19870106
Abstract:
Two-dimensional isothermal diagram for the lateral profile of an atmosphere pressure, fuel rich, premixed, conical LPG/air flame was measured by laser tech- nique.
The local rotational temperature of OH radical for a small zone was detected by the saturated laser induced fluorescence spectroscopy of A ~2∑~+, v′=0←→X ~2Π, v″=0 transition.
The temperature distribution for the flame was measured through moving the position of the burner. The method exhibits the advantages of highly spatial resolution, unturblence, and no need of calibration.
Two-dimensional isothermal diagram for the lateral profile of an atmosphere pressure, fuel rich, premixed, conical LPG/air flame was measured by laser tech- nique.
The local rotational temperature of OH radical for a small zone was detected by the saturated laser induced fluorescence spectroscopy of A ~2∑~+, v′=0←→X ~2Π, v″=0 transition.
The temperature distribution for the flame was measured through moving the position of the burner. The method exhibits the advantages of highly spatial resolution, unturblence, and no need of calibration.
1987, 3(01): 35-41
doi: 10.3866/PKU.WHXB19870107
Abstract:
The crystal structure of the compound RbIO_3·2HIO_3 has been redetermined by heavy-atom method and refined by full matrix least-squares method. The crystal belongs to triclinic system with cell dimensions; a=0.8332 nm, b=0.8232 nm, c=0.8264 nm; α=60.66°, β=85.80°, γ=66.10°. Z= 2, D_m = 4.61 g cm~(-3). The structure is non-centrosymmetric; nevertheless, it has a high degree of centrosymmetry, as a measurement of it, < |△r|>w=0.009 nm. The reliable factor is R=0.076.
Three O atoms are bound to each I atom with mean distance of about 0.18 nm forming a distorted IO_3~- triangular cone; in addition other three neighbour O atoms are bound to it with distances of 0.25—0.33 nm. These six O atoms and their centering I atom form a distorted IO_6 octahedron. Nine O atoms are bound to each Rb atom with distances of 0.286—0.351 nm forming a RbO_9 polyhedron.
The crystal structure of the compound RbIO_3·2HIO_3 has been redetermined by heavy-atom method and refined by full matrix least-squares method. The crystal belongs to triclinic system with cell dimensions; a=0.8332 nm, b=0.8232 nm, c=0.8264 nm; α=60.66°, β=85.80°, γ=66.10°. Z= 2, D_m = 4.61 g cm~(-3). The structure is non-centrosymmetric; nevertheless, it has a high degree of centrosymmetry, as a measurement of it, < |△r|>w=0.009 nm. The reliable factor is R=0.076.
Three O atoms are bound to each I atom with mean distance of about 0.18 nm forming a distorted IO_3~- triangular cone; in addition other three neighbour O atoms are bound to it with distances of 0.25—0.33 nm. These six O atoms and their centering I atom form a distorted IO_6 octahedron. Nine O atoms are bound to each Rb atom with distances of 0.286—0.351 nm forming a RbO_9 polyhedron.
1987, 3(01): 42-47
doi: 10.3866/PKU.WHXB19870108
Abstract:
The film pressure vs. area curves of the surface films of three PLURONIC polyoxyethylene-polypropylene polyols (with molecular weight in the range 2×10~3- 8×10~3) , three all heteric polyoxyethylene-polypropylene polyols (with molecular weight in the range 1.5×10~6-2.5×10~6), and two polypropylene glycols (with mo- lecular weight of 2025 and 2×10~6) have been determined on a saturated sodium nitrate (46%) aqueous solution substrate. Based on the analysis of experimental data, it is proposed that the polyoxyethylene-polyoxypropylene polyols molecule orients at the air/water interface with the EO chain partialy lies in the interface and partially immerses in the water phase. The fraction of the number of EO unit lain in the interface in creases progressively with film pressure, but independent of n_(EO), the ethylene oxide chain length. The same is ture for propylene oxide (PO) chain, except the fraction of the number of PO unit lain in the interface is much smaller than that of the number of EO unit lain in the interface at the same film pressure. With this model and the assumption that the fractions of the number of EO and PO units lain in the interface are independent each other, the surface film data of PLURONIC polyols and all heteric polyoxyethylene-polyoxypropylene polyols can be related with the results of polypropylene glycols and TRITON type surfactants quantitatively. Based on the experimental data of the surface films of three all heteric polyoxyethylene-polyoxypropylene polyols on a pure water surface, it is suggested that in this case the EO chain of the molecule not only is easily soluble in water, but also trends to tring part of PO chain to penetrate the water phase.
The film pressure vs. area curves of the surface films of three PLURONIC polyoxyethylene-polypropylene polyols (with molecular weight in the range 2×10~3- 8×10~3) , three all heteric polyoxyethylene-polypropylene polyols (with molecular weight in the range 1.5×10~6-2.5×10~6), and two polypropylene glycols (with mo- lecular weight of 2025 and 2×10~6) have been determined on a saturated sodium nitrate (46%) aqueous solution substrate. Based on the analysis of experimental data, it is proposed that the polyoxyethylene-polyoxypropylene polyols molecule orients at the air/water interface with the EO chain partialy lies in the interface and partially immerses in the water phase. The fraction of the number of EO unit lain in the interface in creases progressively with film pressure, but independent of n_(EO), the ethylene oxide chain length. The same is ture for propylene oxide (PO) chain, except the fraction of the number of PO unit lain in the interface is much smaller than that of the number of EO unit lain in the interface at the same film pressure. With this model and the assumption that the fractions of the number of EO and PO units lain in the interface are independent each other, the surface film data of PLURONIC polyols and all heteric polyoxyethylene-polyoxypropylene polyols can be related with the results of polypropylene glycols and TRITON type surfactants quantitatively. Based on the experimental data of the surface films of three all heteric polyoxyethylene-polyoxypropylene polyols on a pure water surface, it is suggested that in this case the EO chain of the molecule not only is easily soluble in water, but also trends to tring part of PO chain to penetrate the water phase.
1987, 3(01): 48-54
doi: 10.3866/PKU.WHXB19870109
Abstract:
Open-ring pentadienyl sandwich compounds of 3d metal have been investigated by EHMO method in detail. Some properties of und state for these compounds are obtained. The calculated conformation angles for Ti, V, Cr, Fe are 90°, 90°, 83°, 60°respectively, All these are well in agreement with the values t from the ex- periment.
A further discussion has been made on dependence of the stabilities of dif- ferent geometric configuration of open-ring sandwich compounds upon the δ-bond.
Open-ring pentadienyl sandwich compounds of 3d metal have been investigated by EHMO method in detail. Some properties of und state for these compounds are obtained. The calculated conformation angles for Ti, V, Cr, Fe are 90°, 90°, 83°, 60°respectively, All these are well in agreement with the values t from the ex- periment.
A further discussion has been made on dependence of the stabilities of dif- ferent geometric configuration of open-ring sandwich compounds upon the δ-bond.
1987, 3(01): 55-59
doi: 10.3866/PKU.WHXB19870110
Abstract:
The structure of cryolite-alumina melt has been simulated by Monte Carlo method.It has been found that there exist poly-nuclear ionic clusters with oxygen- bridge or flourine-bridge, such as F_3Al-O-AIF_3, F_3lA—F—AlF_3—F, etc., as well as mono-nuclear ionic clusters such as AlF_5~(2-), AlOF_3~(2-),etc. The melt contains also loose ionic clusters of xNa~+·yF~-. The existence of AlO_2~- or AlO_3~(3-)has been dis- proved by computerized simulation.
The structure of cryolite-alumina melt has been simulated by Monte Carlo method.It has been found that there exist poly-nuclear ionic clusters with oxygen- bridge or flourine-bridge, such as F_3Al-O-AIF_3, F_3lA—F—AlF_3—F, etc., as well as mono-nuclear ionic clusters such as AlF_5~(2-), AlOF_3~(2-),etc. The melt contains also loose ionic clusters of xNa~+·yF~-. The existence of AlO_2~- or AlO_3~(3-)has been dis- proved by computerized simulation.
1987, 3(01): 60-66
doi: 10.3866/PKU.WHXB19870111
Abstract:
The polythiophenes with the benzenoid-like structure, the equibondlength-like structure, and the quinoid-like structure have been calculated by means of LCAO- CO/EHMO. In order to relate the structure of polymer to its unit structure, the thiophene and its dimer and their fragments which are the structural units of poly- mer have also been calculated. The calculation models and the structural parameters are shown in Fig.1. The polythiophene possesses the symmetries of two-fold helix and glide mirror, so that according to Eq.1 and Eq.2 the calculation can be simplified. The NEWBAND-1 computer program depending on LCAO-CO/EHMO is used in our calculation. The ionization potentials and the orbital exponents of valence electrons which we use are lited in Table 1. Five structure units are considered in calculation of the interaction between structure units.
The charge distributions of atoms are shown in Table 2. In our calculation, the 3d orbitals of S atom have been involved and the result is that S atom is negatively charged, but in the paper [10], the 3d orbitals are neglected and the S atom is postively charged. The contribution of atomic orbitals to HOPO (highest occupied polymer orbital) of the polymer is shown in Table 3. It can be seen that there are rather large contributions from the 3p_z and 3d_(xz) orbital of S atom, which is different from the results of VEH etc~[8,10]. So according to our calculation results the electrons in the polythiophene with p-dopant do not only move along C_α—c_β—C_β—C_α skeleton, which is different from the case in the polypyrrole~[14].
The energy bands of three sorts of polythiophenes are shown in Fig.2. Both VBW and CBW shown in Table 4 are quite large, so that whether the dopant is donor or acdeptor, the doped polythiophene will have nice conductivity. From Fig.2 and Table 4 it has been shown that VBW and CBW from type I to III are becoming larger, while the energy gaps are becoming smaller, which is helpful to conduction of doped polythiohene. However, even for the quinoid-like polythiophene its energy gap is still muc larger than kT of therm-motion at the room temperature, so that it is impossible for it to become conductor due to the electron thermexcitation. Th density of valence state of the benzenoid-like polythiophene is shown in Fig.3.
The relationship between the frontier orbitals of polythiophene (I) and its structural units is shown in Fig.4, from which we can find that there is a correlation between them as in the molecular crystal~[15].
According to our calculation, the energy difference ΔE between the structural units of benzenoid-like polythiophene and the quinoid-like polythiophene is 0.124 eV, which is larger than kT of the therm-motion at the room temperature. Thereby, it is still difficult to create polaron or bipolaron in erms of the thermmotion, that is, it is dopant that brings on the polaron or bipolaron.
The polythiophenes with the benzenoid-like structure, the equibondlength-like structure, and the quinoid-like structure have been calculated by means of LCAO- CO/EHMO. In order to relate the structure of polymer to its unit structure, the thiophene and its dimer and their fragments which are the structural units of poly- mer have also been calculated. The calculation models and the structural parameters are shown in Fig.1. The polythiophene possesses the symmetries of two-fold helix and glide mirror, so that according to Eq.1 and Eq.2 the calculation can be simplified. The NEWBAND-1 computer program depending on LCAO-CO/EHMO is used in our calculation. The ionization potentials and the orbital exponents of valence electrons which we use are lited in Table 1. Five structure units are considered in calculation of the interaction between structure units.
The charge distributions of atoms are shown in Table 2. In our calculation, the 3d orbitals of S atom have been involved and the result is that S atom is negatively charged, but in the paper [10], the 3d orbitals are neglected and the S atom is postively charged. The contribution of atomic orbitals to HOPO (highest occupied polymer orbital) of the polymer is shown in Table 3. It can be seen that there are rather large contributions from the 3p_z and 3d_(xz) orbital of S atom, which is different from the results of VEH etc~[8,10]. So according to our calculation results the electrons in the polythiophene with p-dopant do not only move along C_α—c_β—C_β—C_α skeleton, which is different from the case in the polypyrrole~[14].
The energy bands of three sorts of polythiophenes are shown in Fig.2. Both VBW and CBW shown in Table 4 are quite large, so that whether the dopant is donor or acdeptor, the doped polythiophene will have nice conductivity. From Fig.2 and Table 4 it has been shown that VBW and CBW from type I to III are becoming larger, while the energy gaps are becoming smaller, which is helpful to conduction of doped polythiohene. However, even for the quinoid-like polythiophene its energy gap is still muc larger than kT of therm-motion at the room temperature, so that it is impossible for it to become conductor due to the electron thermexcitation. Th density of valence state of the benzenoid-like polythiophene is shown in Fig.3.
The relationship between the frontier orbitals of polythiophene (I) and its structural units is shown in Fig.4, from which we can find that there is a correlation between them as in the molecular crystal~[15].
According to our calculation, the energy difference ΔE between the structural units of benzenoid-like polythiophene and the quinoid-like polythiophene is 0.124 eV, which is larger than kT of the therm-motion at the room temperature. Thereby, it is still difficult to create polaron or bipolaron in erms of the thermmotion, that is, it is dopant that brings on the polaron or bipolaron.
1987, 3(01): 67-73
doi: 10.3866/PKU.WHXB19870112
Abstract:
The ultraviolet spectra of N-substituted phenylglycines (RPhG, R= p-OCH_3, p-CH_3 m-CH_3,-H, m-OCH_3, p-Cl, m-Cl, m-NO_2, p-NO_2) have been studied in n-hexane, n-heptane, dioxane, carbon tetrachloride, benzene, mehtylbenzene, diethyl ether, chlorobenzene,ethyl acetate, ethanol,acetonitrile, 30% ethanol-water, in different ratios of ethanol-n-heptane mixtures by means of Beckman DU-8 Spectrophotometer. The experiment results showed that
1. To compare with the characterized absorption bands of benzene, the bath-ochromic shift of ultraviolet absorption spectra of RPhG in varous solvents was observed. The energy difference between ground state and first excited state of RPhG followed the order
p-OCH_3m-NO_2In 30% ethanol-water the order appeared to be p-NO_22. Linear relationships were found between v of PRhG in various solvents and their base strengths pK_2 and between the transference energy ΔE as well.
3. In non-polar solvents, the frequency v of PRhG varies linearly with the solvent charcterization function f(n~2). In polar solvents, linear relationships did exist between [v-AL_0+B)·f(n~2)] and the solvent characterization function φ(ε)-φ(n~2) and between v of PRhG and f(ε) of solvent as well.
4. In different solvents, linear relationships did exist between the v_R of the same substitutent group of RPhG and the v_H of unsubstituted PhG.
The ultraviolet spectra of N-substituted phenylglycines (RPhG, R= p-OCH_3, p-CH_3 m-CH_3,-H, m-OCH_3, p-Cl, m-Cl, m-NO_2, p-NO_2) have been studied in n-hexane, n-heptane, dioxane, carbon tetrachloride, benzene, mehtylbenzene, diethyl ether, chlorobenzene,ethyl acetate, ethanol,acetonitrile, 30% ethanol-water, in different ratios of ethanol-n-heptane mixtures by means of Beckman DU-8 Spectrophotometer. The experiment results showed that
1. To compare with the characterized absorption bands of benzene, the bath-ochromic shift of ultraviolet absorption spectra of RPhG in varous solvents was observed. The energy difference between ground state and first excited state of RPhG followed the order
p-OCH_3
3. In non-polar solvents, the frequency v of PRhG varies linearly with the solvent charcterization function f(n~2). In polar solvents, linear relationships did exist between [v-AL_0+B)·f(n~2)] and the solvent characterization function φ(ε)-φ(n~2) and between v of PRhG and f(ε) of solvent as well.
4. In different solvents, linear relationships did exist between the v_R of the same substitutent group of RPhG and the v_H of unsubstituted PhG.
1987, 3(01): 74-78
doi: 10.3866/PKU.WHXB19870113
Abstract:
The crystal of (+)-A Triadimenol (baytan) belongs to monoclinic system with space group C_2~2-P2_1 and cell parameters a=1.0543(1) nm, b=0.8202(1) nm, c=0.9778(1) nm, β=113.048(7)°. There are two molecules in each unit cell, Z=2. The X-ray diffraction data were collected on PW-1100 four-circle diffractometer, with CuKα radition. The number of independent diffraction data amounts to 1610, of which 1524 are observable reflections. The crystal structure has been determined by direct method (RANTAN) and refined by full-matrix least-square method to R=0.065. The absolute configuration has been assigned by direct measurement of 18 enantiomer sensitive Bijvoet reflection pairs. X-ray structure analysis shows that absolute configuration of (+)-A triadimenol is 1R, 2S, the triazole ring has an aromatic property.
The crystal of (+)-A Triadimenol (baytan) belongs to monoclinic system with space group C_2~2-P2_1 and cell parameters a=1.0543(1) nm, b=0.8202(1) nm, c=0.9778(1) nm, β=113.048(7)°. There are two molecules in each unit cell, Z=2. The X-ray diffraction data were collected on PW-1100 four-circle diffractometer, with CuKα radition. The number of independent diffraction data amounts to 1610, of which 1524 are observable reflections. The crystal structure has been determined by direct method (RANTAN) and refined by full-matrix least-square method to R=0.065. The absolute configuration has been assigned by direct measurement of 18 enantiomer sensitive Bijvoet reflection pairs. X-ray structure analysis shows that absolute configuration of (+)-A triadimenol is 1R, 2S, the triazole ring has an aromatic property.
1987, 3(01): 79-84
doi: 10.3866/PKU.WHXB19870114
Abstract:
The electronic structures of phthalocyanine molecule (H_2Pc) and phthalocyanine fragment in which four benzene ring are excised (H_2Pc′)are computed by CNDO/2 method. Comparison of the electronic density distribution of two systems shows that disagreement between the theoretic results and the XPS of H_2Pc is mainly ascribed to solid effect. Some disputes on the computation of the elctronic structure of H_2Pc are discussed.
The electronic structures of phthalocyanine molecule (H_2Pc) and phthalocyanine fragment in which four benzene ring are excised (H_2Pc′)are computed by CNDO/2 method. Comparison of the electronic density distribution of two systems shows that disagreement between the theoretic results and the XPS of H_2Pc is mainly ascribed to solid effect. Some disputes on the computation of the elctronic structure of H_2Pc are discussed.
1987, 3(01): 85-87
doi: 10.3866/PKU.WHXB19870115
Abstract:
In this paper XPS studies of (Ph_3P)_3Cu_nX_n complexes have been reported. The XPS shifts of inner shell binding energies show that P→Cu dative bond exists in (Ph_3P)_3Cu_nX_n complexes. The large shifts of Cu 2P_(3/2) and P 2d binding energies of (Ph_3P)_3Cu(CN) and (Ph_3P)_3Cu_2(CN)_2 complexes are due to the feedback effect of Cu 3d~(10) electrons. The results XPS shake-up satellite peaks furthermore confirm the existence of P→Cu dative bond in these complexes. In addition, XPS valence band spectra of these complexes appear to be superposition from the XPS valence band spectra of CuX and Ph_3P.
In this paper XPS studies of (Ph_3P)_3Cu_nX_n complexes have been reported. The XPS shifts of inner shell binding energies show that P→Cu dative bond exists in (Ph_3P)_3Cu_nX_n complexes. The large shifts of Cu 2P_(3/2) and P 2d binding energies of (Ph_3P)_3Cu(CN) and (Ph_3P)_3Cu_2(CN)_2 complexes are due to the feedback effect of Cu 3d~(10) electrons. The results XPS shake-up satellite peaks furthermore confirm the existence of P→Cu dative bond in these complexes. In addition, XPS valence band spectra of these complexes appear to be superposition from the XPS valence band spectra of CuX and Ph_3P.
1987, 3(01): 88-91
doi: 10.3866/PKU.WHXB19870116
Abstract:
In this paper, the interactions between acenaphthene (AC) and 1,4-dicyano- benzene(p-DCB) and between AC and 1, 3-dicyanobenzene(m-DCB) were studied. The results show that both systems can form exciplex but the peak positions of the two exciplex are different. For AC-pDCB, the peak position of exciplex is si- tuated at 420-425 nm but for AC-mDCB, it is around 410-415 nm. These facts indicate that the interaction between AC-pDCB is stronger than AC-mDCB. On the other hand, fluorescence quenching of acenaphthene by DCB are deviated from Stern-Volmer rule at higher concentrations of DCB. This phenomenon can be explained by the principle of sphere of action. Radius of action sphere are 1.4 nm and 1.2 nm respectively for AC-pDCB and AC-mDCB. Fluorescence decays of AC at different concentrations of pDCB or mDCB were also measured. Single exponential decay formula is obeyed for all of the measurements. From the experimental data of fluorescence decay, k_3/k_4 of both systems were calculated.
In this paper, the interactions between acenaphthene (AC) and 1,4-dicyano- benzene(p-DCB) and between AC and 1, 3-dicyanobenzene(m-DCB) were studied. The results show that both systems can form exciplex but the peak positions of the two exciplex are different. For AC-pDCB, the peak position of exciplex is si- tuated at 420-425 nm but for AC-mDCB, it is around 410-415 nm. These facts indicate that the interaction between AC-pDCB is stronger than AC-mDCB. On the other hand, fluorescence quenching of acenaphthene by DCB are deviated from Stern-Volmer rule at higher concentrations of DCB. This phenomenon can be explained by the principle of sphere of action. Radius of action sphere are 1.4 nm and 1.2 nm respectively for AC-pDCB and AC-mDCB. Fluorescence decays of AC at different concentrations of pDCB or mDCB were also measured. Single exponential decay formula is obeyed for all of the measurements. From the experimental data of fluorescence decay, k_3/k_4 of both systems were calculated.
1987, 3(01): 92-96
doi: 10.3866/PKU.WHXB19870117
Abstract:
Ethylene oxde is catalytically dissociated on silver surface. The first step of this reaction is to isomerize to acetyl aldehyde. The single collision catalytic di- ssociation probability is several orders of magnitude higher than the unimolecular reaction probability calculated by RRKM theory. Its activation energy decresese from 238 kJ mol~(-1) TO 42.6 kJ mol~(-1). The reaction order, reaction mechanism and product yield of this reaction are also described. These results will be helpful for the production of ethylene in industrial scale.
Ethylene oxde is catalytically dissociated on silver surface. The first step of this reaction is to isomerize to acetyl aldehyde. The single collision catalytic di- ssociation probability is several orders of magnitude higher than the unimolecular reaction probability calculated by RRKM theory. Its activation energy decresese from 238 kJ mol~(-1) TO 42.6 kJ mol~(-1). The reaction order, reaction mechanism and product yield of this reaction are also described. These results will be helpful for the production of ethylene in industrial scale.
1987, 3(01): 97-101
doi: 10.3866/PKU.WHXB19870118
Abstract:
The title compound has been synthesized under nitrogen atmosphere using V_2O_5 for the initiator by Schlenk techniques. It′s single crystal, which is very air and water-sensitive, was obtained and determined from three-dimensinal x-ray diffraction data collected by the four-circle diffractometer. The crystals are orth- orhombic with space group D_2~4-P_(212121) and unit cell constants a=0.909 nm, b=1.4909 nm, c=2.1635 nm and z=4.
We derived first the positional parameters of V, Zn, Cland O atoms by direct method using SHELXTL program. The coordinates of other the non-hyleast-squares refinement for all atoms gave a final discrepency factor R=0.0945 and RW=0.0674.
The result of structure analysis shows that the compound is composed of the octahedral cation [VCl_2·(THF)_4]~+ and the tetrahedral anion [ZnCl_3·THF]~-.
The reaction mechanism was discussed. The title compound is reaction product of VCl_3 with ZnCl_2 in THF.
The title compound has been synthesized under nitrogen atmosphere using V_2O_5 for the initiator by Schlenk techniques. It′s single crystal, which is very air and water-sensitive, was obtained and determined from three-dimensinal x-ray diffraction data collected by the four-circle diffractometer. The crystals are orth- orhombic with space group D_2~4-P_(212121) and unit cell constants a=0.909 nm, b=1.4909 nm, c=2.1635 nm and z=4.
We derived first the positional parameters of V, Zn, Cland O atoms by direct method using SHELXTL program. The coordinates of other the non-hyleast-squares refinement for all atoms gave a final discrepency factor R=0.0945 and RW=0.0674.
The result of structure analysis shows that the compound is composed of the octahedral cation [VCl_2·(THF)_4]~+ and the tetrahedral anion [ZnCl_3·THF]~-.
The reaction mechanism was discussed. The title compound is reaction product of VCl_3 with ZnCl_2 in THF.
1987, 3(01): 102-108
Abstract:
