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1.
l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate,
[ \textPV\textV \textV\textV \textW 1 0 \textO 4 0 ]5 - , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the
reaction are cystine and two electron-reduced heteropoly blue, [PVIVVIVW10O40]7−. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C.
The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order
kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction
proceeds through an outer-sphere mechanism. For the dianion −SCH2CH(NH3
+)COO−, the rate constant for the cross electron transfer reaction is 96 M−1s−1 at 25 °C. The self-exchange rate constant for the
- \textSCH2 \textCH( \textNH3 + )\textCOO - \mathord | / |
\vphantom - \textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } \mathord{\left/ {\vphantom {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }}} \right. \kern-\nulldelimiterspace} {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }} couple was evaluated using the Rehm–Weller relationship. 相似文献
2.
Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates,
[ \text PV\textV \text W 1 1 \text O 4 0 ] 4 - [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and
[ \text PV\textV \text V\textV \text W 1 0 \text O 4 0 ] 5 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} ]^{{ 5 { - }}} (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous
medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue,
[ \text PV\textIV \text W 1 1 \text O 40 ] 5- [ {\text{PV}}^{\text{IV}} {\text{W}}_{ 1 1} {\text{O}}_{ 40} ]^{ 5- } . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue
[ \text PV\textIV \text V\textIV \text W 10 \text O 40 ] 7- [ {\text{PV}}^{\text{IV}} {\text{V}}^{\text{IV}} {\text{W}}_{ 10} {\text{O}}_{ 40} ]^{ 7- } . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and
order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H +], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed
and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and
[ \text PV\textV \text V\textV \text V\textV \text W 9 \text O 4 0 ] 6 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 9} {\text{O}}_{ 4 0} ]^{{ 6 { - }}} (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards
penicillin G. 相似文献
3.
The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H 2O)] −2 by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically over the pH 6.10–7.02 range at 25 °C.
The reaction is first-order with respect to complex and the oxidant, and it obeys the following rate law:
\textRate = k\textet K 2 K 3 [ \textCo\textII ( \textEDTA )( \textH 2 \textO ) - 2 ]\textT [\textNBS] \mathord | / |
\vphantom [\textNBS] ( [ \textH + ] + K 2 ) ( [ \textH + ] + K 2 ) {\text{Rate}} = k^{\text{et} } K_{ 2} K_{ 3} \left[ {{\text{Co}}^{\text{II}} \left( {\text{EDTA}} \right)\left( {{\text{H}}_{ 2} {\text{O}}} \right)^{ - 2} } \right]_{\text{T}} {{[{\text{NBS}}]} \mathord{\left/ {\vphantom {{[{\text{NBS}}]} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}} 相似文献
4.
Combustion calorimetry, Calvet-drop sublimation calorimetry, and the Knudsen effusion method were used to determine the standard
( p
o = 0.1 MPa) molar enthalpies of formation of monoclinic (form I) and gaseous paracetamol, at T = 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) = - ( 4 10.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) = - ( 2 80.5 ±1. 9)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) = - ( 2 80.5 \pm 1. 9){\text{ kJ}}\;{\text{mol}}^{ - 1} . From the obtained
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) value and published data, it was also possible to derive the standard molar enthalpies of formation of the two other known
polymorphs of paracetamol (forms II and III), at 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crII}}} \right) = - ( 40 8.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crIII}}} \right) = - ( 40 7.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} . The proposed
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) value, together with the experimental enthalpies of formation of acetophenone and 4′-hydroxyacetophenone, taken from the
literature, and a re-evaluated enthalpy of formation of acetanilide,
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text ON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ \text mol - 1 , \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{ON}},{\text{ g}}} \right) = - ( 10 9. 2\,\pm\,2. 2){\text{ kJ}}\;{\text{mol}}^{ - 1} , were used to assess the predictions of the B3LYP/cc-pVTZ and CBS-QB3 methods for the enthalpy of a isodesmic and isogyric
reaction involving those species. This test supported the reliability of the theoretical methods, and indicated a good thermodynamic
consistency between the
\Updelta \textf H\textm\texto \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} (C 8H 9O 2N, g) value obtained in this study and the remaining experimental data used in the
\Updelta \textr H\textm\texto \Updelta_{\text{r}} H_{\text{m}}^{\text{o}} calculation. It also led to the conclusion that the presently recommended enthalpy of formation of gaseous acetanilide in
Cox and Pilcher and Pedley’s compilations should be corrected by ~20 kJ mol −1. 相似文献
5.
Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O 3–N 2 sigma bond is due to $ n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries
obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O3–N2 sigma bond is due to
n\textO1 ? s\textO3 - \textN2 * n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} delocalization and is responsible for the longer O3–N2 bond lengths in para-substituted O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} orbital in the idealized Lewis structure, or increased occupancy of
s\textO3 - \textN2 * \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with
the resulting p character of the corresponding sulfur natural hybrid orbital of
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of substituent
groups and the partial charges distribution on the skeletal atoms may approve anticipating that the electrostatic repulsion
or attraction between atoms can give a significant contribution to the intra- and intermolecular interaction. 相似文献
6.
The standard molar Gibbs free energy of formation of YRhO 3(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte.
The cell can be represented by:
( - )\text Pt - Rh/{ \text Y2\text O\text3( \text s ) + \text YRh\text O3( \text s ) + \text Rh( \text s ) }//\text CSZ//\text O2( p( \text O2 ) = 21.21 \text kPa )/\text Pt - Rh( + ) \left( - \right){\text{Pt - Rh/}}\left\{ {{{\text{Y}}_2}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right) + {\text{Rh}}\left( {\text{s}} \right)} \right\}//{\text{CSZ//}}{{\text{O}}_2}\left( {p\left( {{{\text{O}}_2}} \right) = 21.21\;{\text{kPa}}} \right)/{\text{Pt - Rh}}\left( + \right) . The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of
the formation of YRhO 3(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by:
D \textfG\texto{ \text YRh\text O3( \text s ) }/\text kJ \text mo\text l - 1( ±1.61 ) = - 1,147.4 + 0.2815 T ( \text K ) {\Delta_{\text{f}}}{G^{\text{o}}}\left\{ {{\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right)} \right\}/{\text{kJ}}\;{\text{mo}}{{\text{l}}^{ - 1}}\left( {\pm 1.61} \right) = - 1,147.4 + 0.2815\;T\;\left( {\text{K}} \right) . Standard molar heat capacity Cop,m C^{o}_{{p,m}} ( T) of YRhO 3(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to
299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can
be represented by: $ {*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ $ \begin{array}{*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ \end{array} The heat capacity of YRhO 3(s) was used along with the data obtained from the electrochemical cell to calculate the standard enthalpy and entropy of
formation of the compound at 298.15 K. 相似文献
7.
Extraction of microamounts of cesium by a nitrobenzene solution of ammonium dicarbollylcobaltate
( \text NH 4 + \text B - ) ( {{\text{NH}}_{ 4}^{ + } {\text{B}}^{ - } }) and thallium dicarbollylcobaltate
( \text Tl + \text B - ) ( {{\text{Tl}}^{ + } {\text{B}}^{ - } }) in the presence of 2,3-naphtho-15-crown-5 (N15C5, L) has been investigated. The equilibrium data have been explained assuming
that the complexes
\text ML + {\text{ML}}^{ + } and
\text ML 2 + {\text{ML}}_{ 2}^{ + }
( \text M + = \text NH4 + ,\text Tl + ,\text Cs + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } } ) are present in the organic phase. The stability constants of the
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + } species
( \text M + = \text NH4 + ,\text Tl + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } }) in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + }
(\text M + = \text NH4 + ,\text Tl + ,\text Cs + ; \text L = \text N15\text C5) ({{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } ;\;{\text{L}} = {\text{N}}15{\text{C}}5}) in the mentioned medium increases in the
\text Cs + < \text NH4 + < \text Tl + {\text{Cs}}^{ + }\,<\, {\text{NH}}_{4}^{ + }\,<\,{\text{Tl}}^{ + } order. 相似文献
8.
A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy( m-NBA) 3phen] 2·4H 2O ( m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H 2O(s)], [6 m-HNBA(s)], [2DyCl 3·6H 2O(s)], and [Dy( m-NBA) 3phen] 2·4H 2O(s) in the calorimetric solvent (V DMSO:V MeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H 2O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6 m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl 3·6H 2O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol −1, and
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol −1, respectively. The enthalpy change of the reaction was determined to be
\Updelta \textr H\textmq = 3 6 9. 4 9 ±0. 5 6 \text kJ·\text mol - 1 . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of
formation of [Dy( m-NBA) 3phen] 2·4H 2O(s) was estimated to be
\Updelta \textf H\textmq \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = −5525 ± 6 kJ·mol −1. 相似文献
9.
Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H +B −) in the presence of diphenyl- N,N-dibutylcarbamoylmethyl phosphine oxide (DPDBCMPO, L) has been investigated. The equilibrium data have been explained assuming
that the species HL +,
\text HL2 + {\text{HL}}_{2}^{ + } , CaL 2+,
\text CaL 2 2 + {\text{CaL}}_{ 2}^{{ 2 { + }}} ,
\text CaL 3 2 + {\text{CaL}}_{ 3}^{{ 2 { + }}} , SrL 2+,
\text SrL 2 2 + {\text{SrL}}_{ 2}^{{ 2 { + }}} ,
\text SrL 3 2 + {\text{SrL}}_{ 3}^{{ 2 { + }}} and
\text SrL 4 2 + {\text{SrL}}_{ 4}^{{ 2 { + }}} are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene
saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants
of the complexes CaL 2+,
\text CaL 2 2 + {\text{CaL}}_{ 2}^{{ 2 { + }}} and
\text CaL 3 2 + {\text{CaL}}_{ 3}^{{ 2 { + }}} , where L is DPDBCMPO, are somewhat higher than those of the corresponding complex species SrL 2+,
\text SrL 2 2 + {\text{SrL}}_{ 2}^{{ 2 { + }}} and
\text SrL 3 2 + {\text{SrL}}_{ 3}^{{ 2 { + }}} . 相似文献
10.
Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H +B −) in the presence of polyethylene glycol PEG 1000 (L) has been investigated. The equilibrium data have been explained assuming
that the complexes
\text H 2 \text L2 + {\text{H}}_{ 2} {\text{L}}^{2 + } ,
\text ML 2+ {\text{ML}}^{ 2+ } and
\text MHL 3+ {\text{MHL}}^{ 3+ }
( \text M 2+ = \text Sr 2+ , \text Ba 2+ ) \left( {{\text{M}}^{ 2+ } = {\text{Sr}}^{ 2+ } ,\,\,{\text{Ba}}^{ 2+ } } \right) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. It was found that in water-saturated nitrobenzene the stability constant of the
\text BaL 2+ {\text{BaL}}^{ 2+ } cationic complex species is somewhat higher than that of the complex
\text SrL 2+ {\text{SrL}}^{ 2+ } . 相似文献
11.
Electrospray ionization coupled with low energy collision induced dissociation (CID) in an ion trap mass spectrometer was
used to examine the fragmentation patterns of the [M + Na] + of eight pairs of heptapeptides containing α- or β-Asp residues in second and sixth amino acid positions, respectively. Selective
cleavages at the peptide backbone C-terminal to two Asp residues were observed, which generated a series of C-terminal y 5 ions and N-terminal b 6 ions. Two typical ions:
[ \text y5 + \text Na-\text H ] + {\left[ {{{\text{y}}_{{5}}} + {\text{Na}}-{\text{H}}} \right]^{ + }} and
[ \text b6 + \text Na + \text OH ] + {\left[ {{{\text{b}}_{{6}}} + {\text{Na}} + {\text{OH}}} \right]^{ + }} , produced by α-Asp containing peptides were noted to be much more abundant than those of the peptides with β-Asp, which could
be used for distinction of the isomers in Asp2 and Asp6, respectively. In addition, a series of internal ions generated by
simultaneous cleavages at Asp residues were detected. Competitive reactions of carboxylic groups occurred between Asp6 side
chain and C-terminus. Formation mechanisms of most product ions are proposed. The results obtained in this work are significant
since low energy CID has been demonstrated to be effective for the distinction of Asp isomers. 相似文献
12.
The formation of large even-numbered carbon cluster anions,
\text C\textn - {\text{C}}_{\text{n}}^{ - } , with n up to 500 were observed in the mass spectra generated by laser ablation of graphene and graphene oxide, and the signal
intensity of the latter is much weaker than that of the former. The cluster distributions generated from graphene can be readily
altered by changing the laser energy and the accumulation period in the FT - ICR cell. By choosing suitable experimental conditions,
weak signals of odd-numbered anions from
\text C125 - {\text{C}}_{{125}}^{ - } to
\text C211 - {\text{C}}_{{211}}^{ - } , doubly charged anions from
\text C702 - {\text{C}}_{{70}}^{{2 - }} to
\text C2302 - {\text{C}}_{{230}}^{{2 - }} and triply charged cluster anions from
\text C803 - {\text{C}}_{{80}}^{{3 - }} to
\text C2243 - {\text{C}}_{{224}}^{{3 - }} can be observed. Tandem MS was applied to some selected cluster anions. Though no fragment anions larger than
\text C20 - {\text{C}}_{{20}}^{ - } can be observed by the process of collisional activation with N 2 gas for most cluster ions, several cluster anions can lose units of C 2, C 4, C 6 or C 8 in their collision process. The differences in their dissociation kinetics and structures require further calculations and
experimental studies. 相似文献
13.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M + (aq) + NaL + (nb) ⇔ ML + (nb) + Na + (aq) taking place in the two-phase water–nitrobenzene system (M + = H 3O +,
\text NH4+ {\text{NH}}_{4}{}^{+} , Ag +, Tl +; L = hexaethyl p- tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants
of the ML + complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order:
\text Ag + < NH 4 + < \text H 3 \text O + < \text Na + < \text Tl + . {\text{Ag}}^{ + } \, < \,\hbox{NH}_{4}{}^{ + } \, < \,{\text{H}}_{ 3} {\text{O}}^{ + } \, < \,{\text{Na}}^{ + } \, < \,{\text{Tl}}^{ + }. 相似文献
14.
We have established and analyzed the sequences of phase transitions in synthesis of layered compounds in the A nB n–1O 3n family (
\text A3\textII\text LnB3\textV\text O12 {\text{A}}_3^{\text{II}}{\text{LnB}}_3^{\text{V}}{{\text{O}}_{{12}}} (A II = Ba, Sr, Ln = La, Nd, B V = Nb, Ta) and La 4Ti 3O 12 with n = 4) from coprecipitated hydroxocarbonate and hydroxide systems, including steps involving the formation, solid-phase
reaction, or structural rearrangement of intermediates. 相似文献
15.
This article reports the values of the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase,
\Updelta \textf H\textm\texto ( \text g ), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{g}} \right), at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol −1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase,
\Updelta \textf H\textm\texto ( \text cr ) , {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{cr}} \right) , at T = 298.15 K, obtained from the standard molar enthalpies of combustion,
\Updelta \textc H\textm\texto , {{\Updelta}}_{\text{c}} H_{\text{m}}^{\text{o}} , measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method.
The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted
thiophene ring is compared with the same contribution in other structurally similar compounds. 相似文献
16.
Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H +B −) in the presence of tetraisopropyl methylene diphosphonate [T(iPr)MDP, L] has been investigated. The equilibrium data have
been explained assuming that the species HL +,
\text HL2 + {\text{HL}}_{2}^{ + } ,
\text ML22 + {\text{ML}}_{2}^{2 + } and
\text ML32 + {\text{ML}}_{3}^{2 + } (M 2+ = Ca 2+, Sr 2+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene
saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability constants
of the
\text CaLn2 + {\text{CaL}}_{n}^{2 + } complexes, where n = 2, 3 and L is T(iPr)MDP, are somewhat higher than those of the corresponding complex species
\text SrLn2 + {\text{SrL}}_{n}^{2 + } . 相似文献
17.
The mixed-valence 24-vanadophosphate
( 1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal
X-ray analysis was carried out on ( Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru IIIO 6 octahedra, 2 V IVO 6 octahedra, 14 V VO 5 square-pyramids, 8 V VO 4 tetrahedra, and 2 PO 4 tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru II( dmso) 3 groups. XPS studies on Na-1 confirm the presence of 2 Ru III and 6 Ru II as well as 22 V V and 2 V IV centers. Magnetic susceptibility data on Na-1 show that the V IV–Ru III pairs are coupled antiferromagnetically, with J
1 = −13 K and J
2 ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state.
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In Memoriam Prof. F. A. Cotton 相似文献
18.
The influence of the electronic properties of oxidized Nb surfaces on the electrodeposition of metals (Me=Co, Cu, Ag) with
different equilibrium potentials is studied by conventional electrochemical techniques and atomic force microscopy. The results show that relatively thin
anodic Nb 2O 5 films (thickness <11 nm) present a frequency-dependent n-type semiconductor behavior, which can be described by the theory
of amorphous semiconductor. The Schottky barrier, formed at the a-Nb 2O 5/electrolyte interface, affects the deposition rate of metals with equilibrium potentials more positive than the flat band
potential Then, the dependence of density of states on the oxide thickness and anodization conditions leads to different extents of
the band bending, affecting directly the rate of electron transfer. 相似文献
19.
In the present work the uranyl hexacyanoferrate (K 2UO 2[Fe(CN) 6]) is deposited on the palladized aluminum (Pd-Al) electrode from a
\text UO22 + + \text Fe( \text CN ) 6 - 3 {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K 2UO 2[Fe(CN) 6] from the Pd-Al surface. The operational conditions including: pH, K 3Fe(CN) 6 concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was
linear in concentration range 10–460 μM. of
\text UO22 + {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K 2UO 2[Fe(CN) 6] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores. 相似文献
20.
Three new binuclear copper complexes of formulae $ \left[ {{\text{Cu}}_{2}^{\text{II}} {\text{Pz}}_{2}^{\text{Me3}} {\text{Br}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ ( 1), $ \left[ {{\text{Cu}}_{ 2}^{\text{II}} {\text{Pz}}_{2}^{\text{Ph2Me}} {\text{Cl}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ ( 2) and $ \left[ {{\text{Cu}}_{2}^{\text{II}} \left( {{\text{Pz}}^{\text{PhMe}} } \right)_{ 4} {\text{Cl}}_{ 4} } \right] $ ( 3) (Pz Me3?=?3,4,5-trimethylpyrazole, Pz Ph2Me?=?4-methyl-3,5-diphenylpyrazole and Pz PhMe?=?3-methyl-5-phenylpyrazole) have been synthesized and characterized by chemical analysis, FTIR and 31P NMR spectroscopy and single-crystal X-ray diffraction. Complex 1 is a doubly bromo-bridged dimer, while complexes 2 and 3 are chloro-bridged dimers. The Cu(II) centers are in a distorted tetrahedral geometry for 1 and 2 and a distorted square pyramidal N 2Cl 3 environment for 3. 相似文献
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