M. Raimondi, M. Sironi, J. Gerratt, D. L. Cooper, P. Karadakov
Modern valence bond theory, in its spin-coupled form, is used to investigate the bonding in fluorocyclophosphazenes. We find that the spin-coupled orbitals for the ‘out-of-plane’ π system split into two sets. One of these consists of slightly deformed pπ functions that are fairly tightly localised on N atoms. The other set consists of functions that are also associated with individual N atoms but which also show significant delocalisation onto the neighbouring P atoms. The pairs associated with a given N atom are predominantly singlet coupled. It is found that the d basis functions used here for phosphorus play only a minor role, as polarisation functions. The same is true for the d functions on nitrogen. The spin-coupled description of the bonding, which is intermediate between the simplistic zwitterionic and covalent models, may be envisaged as a sequence of highly polarised Nδ-–Pδ+ bonds.
{"title":"Spin-coupled description of fluorocyclophosphazenes (NPF2)3, (NPF2)4, (NPF2)5","authors":"M. Raimondi, M. Sironi, J. Gerratt, D. L. Cooper, P. Karadakov","doi":"10.1039/A708127H","DOIUrl":"https://doi.org/10.1039/A708127H","url":null,"abstract":"Modern valence bond theory, in its spin-coupled form, is used to investigate the bonding in fluorocyclophosphazenes. We find that the spin-coupled orbitals for the ‘out-of-plane’ π system split into two sets. One of these consists of slightly deformed pπ functions that are fairly tightly localised on N atoms. The other set consists of functions that are also associated with individual N atoms but which also show significant delocalisation onto the neighbouring P atoms. The pairs associated with a given N atom are predominantly singlet coupled. It is found that the d basis functions used here for phosphorus play only a minor role, as polarisation functions. The same is true for the d functions on nitrogen. The spin-coupled description of the bonding, which is intermediate between the simplistic zwitterionic and covalent models, may be envisaged as a sequence of highly polarised Nδ-–Pδ+ bonds.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"76 1","pages":"1541-1545"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88022920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The H–D exchange reaction between methane and deuteriated potassium amide supported on alumina (KND2/Al2O3), a strongly basic catalyst, has been investigated by FTIR spectroscopy. KND2/Al2O3 was prepared by contacting KNH2/Al2O3 with D2 at 373 K for 30 min. The N–D asymmetric and symmetric bands in KND2 were observed at 2411 and 2343 cm−1. The ND2 bending bands were observed at 1132 cm−1. The H–D exchange reaction between CH4 and KND2 proceeded at room temperature. First, the N–H bands in KNDH were observed at 3210 cm−1. and then KNDH was further converted to KNH2, whose N–H stretching bands were observed at 3238 and 3190 cm−1. The H–D exchange reaction between ethane and KND2/Al2O3 also proceeded at room temperature, but the rate was slower than that between methane and KND2/Al2O3. The lower reactivity of ethane indicates a carbanion mechanism since the acidity (pKa) of ethane (42) is lower than that of methane (40).
{"title":"H–D Exchange between methane and deuteriated potassium amide supported on alumina","authors":"H. Handa, T. Baba, Y. Ono","doi":"10.1039/A706059I","DOIUrl":"https://doi.org/10.1039/A706059I","url":null,"abstract":"The H–D exchange reaction between methane and deuteriated potassium amide supported on alumina (KND2/Al2O3), a strongly basic catalyst, has been investigated by FTIR spectroscopy. KND2/Al2O3 was prepared by contacting KNH2/Al2O3 with D2 at 373 K for 30 min. The N–D asymmetric and symmetric bands in KND2 were observed at 2411 and 2343 cm−1. The ND2 bending bands were observed at 1132 cm−1. The H–D exchange reaction between CH4 and KND2 proceeded at room temperature. First, the N–H bands in KNDH were observed at 3210 cm−1. and then KNDH was further converted to KNH2, whose N–H stretching bands were observed at 3238 and 3190 cm−1. The H–D exchange reaction between ethane and KND2/Al2O3 also proceeded at room temperature, but the rate was slower than that between methane and KND2/Al2O3. The lower reactivity of ethane indicates a carbanion mechanism since the acidity (pKa) of ethane (42) is lower than that of methane (40).","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"73 1","pages":"451-454"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86099877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A kinetic model for chemical reactions in the mesosphere, previously shown to support simple and complex oscillatory responses, is examined. The underlying chemical origins of the change between different oscillatory responses is rationalised in terms of the evolution of the concentrations of the HOx species. Mechanism and variable reduction methods are employed to produce a 12 reaction scheme with two dynamic variable concentrations ([H] and [O], with [OH], [HO2] and [O3] treated through the dynamic steady-state approximation). The reduced model is used to investigate the effect of species transport longitudinally. The latter shows that complex responses can still arise, but that high transport rates eventually lead to a synchronous state in which the concentrations of the species become effectively constant in space and time.
{"title":"A reduced model for complex oscillatory responses in the mesosphere","authors":"Barry R. Johnson, S. Scott, M. Tinsley","doi":"10.1039/A804150D","DOIUrl":"https://doi.org/10.1039/A804150D","url":null,"abstract":"A kinetic model for chemical reactions in the mesosphere, previously shown to support simple and complex oscillatory responses, is examined. The underlying chemical origins of the change between different oscillatory responses is rationalised in terms of the evolution of the concentrations of the HOx species. Mechanism and variable reduction methods are employed to produce a 12 reaction scheme with two dynamic variable concentrations ([H] and [O], with [OH], [HO2] and [O3] treated through the dynamic steady-state approximation). The reduced model is used to investigate the effect of species transport longitudinally. The latter shows that complex responses can still arise, but that high transport rates eventually lead to a synchronous state in which the concentrations of the species become effectively constant in space and time.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"51 1","pages":"2709-2715"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86105421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Okamoto, T. Kubota, Hideki Gotoh, Yoshiharu Ohto, H. Aritani, Tsunehiro Tanaka, S. Yoshida
A Cu/ZrO2 (1 wt.% Cu) catalyst shows high activity for the NO–CO reaction, even at low temperature (100–200 °C). However, the low-temperature activity is easily lost during prolonged reaction at 250 °C. The activity of the deactivated Cu/ZrO2 catalyst is completely restored by NO treatment (1% in He) at >250 °C or O2 treatment (5% in He) at 500 °C. The addition of iron (2 wt.%) to Cu/ZrO2 causes not only a dramatic increase in the low-temperature activity but also high stability against deactivation. An X-ray absorption fine structure (XAFS) study has been conducted to reveal the local structure and chemical state of the Cu species in Cu/ZrO2 and Cu–Fe/ZrO2 during the reaction and rejuvenation. X-ray absorption near-edge structure (XANES) spectra and, in particular, their first derivatives are shown to be very effective for characterization of the Cu species. It is revealed that the deactivation of Cu/ZrO2 is a consequence of reduction and sintering of highly dispersed Cu+ species, derived from Cu2+(Oct) species in an octahedral symmetry, to Cu metal particles. The Cu metal particles in a deactivated Cu/ZrO2 catalyst are transformed into the original Cu2+(Oct) species by the NO treatment at 250 °C via highly dispersed Cu+ species. On the other hand, O2 treatments bring about successive formation of Cu2O at 150 °C and CuO at 250 °C. The Cu2+(Oct) species are reformed at >400 °C. The XAFS study of Cu–Fe/ZrO2 suggests that the high stability of highly dispersed Cu+ species is a consequence of direct interaction of Cu species with iron oxide clusters. On the basis of kinetics and XAFS results, the catalytic synergies between Cu and Fe are inferred to be two-fold: stabilization of highly dispersed and catalytically active Cu+ species during the reaction and simultaneous participation of both Cu and Fe in the reaction.
Cu/ZrO2 (1 wt.% Cu)催化剂在低温(100 ~ 200℃)下对NO-CO反应具有较高的催化活性。然而，在250°C的长时间反应中，低温活性很容易丧失。失活Cu/ZrO2催化剂在>250℃时经NO处理(He含量为1%)或500℃时O2处理(He含量为5%)可完全恢复活性。在Cu/ZrO2中加入2 wt.%的铁，不仅可以显著提高Cu/ZrO2的低温活性，还可以提高Cu/ZrO2的抗失活稳定性。通过x射线吸收精细结构(XAFS)研究揭示了Cu/ZrO2和Cu - fe /ZrO2在反应和回春过程中的局部结构和化学状态。x射线吸收近边结构(XANES)光谱，特别是它们的一阶导数被证明是非常有效的表征Cu物种。结果表明，Cu/ZrO2的失活是由Cu2+(Oct)在八面体对称中形成的高度分散的Cu+还原和烧结成Cu金属颗粒的结果。失活Cu/ZrO2催化剂中的Cu金属颗粒经250℃NO处理后，通过高度分散的Cu+形态转化为原始Cu2+(Oct)形态。另一方面，O2处理在150°C和250°C时连续生成Cu2O。Cu2+(Oct)在>400℃时发生重整。Cu - fe /ZrO2的XAFS研究表明，高度分散的Cu+物种的高稳定性是Cu物种与氧化铁团簇直接相互作用的结果。根据动力学和XAFS结果，Cu和Fe之间的催化协同作用可以推断为双重的:在反应过程中高度分散和催化活性的Cu+物种的稳定以及Cu和Fe同时参与反应。
{"title":"XAFS study of zirconia-supported copper catalysts for the NO–CO reaction: Deactivation, rejuvenation and stabilization of Cu species","authors":"Y. Okamoto, T. Kubota, Hideki Gotoh, Yoshiharu Ohto, H. Aritani, Tsunehiro Tanaka, S. Yoshida","doi":"10.1039/A807152G","DOIUrl":"https://doi.org/10.1039/A807152G","url":null,"abstract":"A Cu/ZrO2 (1 wt.% Cu) catalyst shows high activity for the NO–CO reaction, even at low temperature (100–200 °C). However, the low-temperature activity is easily lost during prolonged reaction at 250 °C. The activity of the deactivated Cu/ZrO2 catalyst is completely restored by NO treatment (1% in He) at >250 °C or O2 treatment (5% in He) at 500 °C. The addition of iron (2 wt.%) to Cu/ZrO2 causes not only a dramatic increase in the low-temperature activity but also high stability against deactivation. An X-ray absorption fine structure (XAFS) study has been conducted to reveal the local structure and chemical state of the Cu species in Cu/ZrO2 and Cu–Fe/ZrO2 during the reaction and rejuvenation. X-ray absorption near-edge structure (XANES) spectra and, in particular, their first derivatives are shown to be very effective for characterization of the Cu species. It is revealed that the deactivation of Cu/ZrO2 is a consequence of reduction and sintering of highly dispersed Cu+ species, derived from Cu2+(Oct) species in an octahedral symmetry, to Cu metal particles. The Cu metal particles in a deactivated Cu/ZrO2 catalyst are transformed into the original Cu2+(Oct) species by the NO treatment at 250 °C via highly dispersed Cu+ species. On the other hand, O2 treatments bring about successive formation of Cu2O at 150 °C and CuO at 250 °C. The Cu2+(Oct) species are reformed at >400 °C. The XAFS study of Cu–Fe/ZrO2 suggests that the high stability of highly dispersed Cu+ species is a consequence of direct interaction of Cu species with iron oxide clusters. On the basis of kinetics and XAFS results, the catalytic synergies between Cu and Fe are inferred to be two-fold: stabilization of highly dispersed and catalytically active Cu+ species during the reaction and simultaneous participation of both Cu and Fe in the reaction.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"2016 1","pages":"3743-3752"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86429113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Fajardie, ois Tempere, J. Manoli, G. Djéga-Mariadassou, G. Blanchard
Rh/CeO2 systems prepared by anionic exchange of anionic rhodium chloro complexes contain significant amounts of chloride. They are referred to as Rh(Cl)/CeO2 catalysts. Reduction at 1173 K does not decrease the chloride content of these catalysts but calcination in air at the same temperature leads to total elimination of Cl− ions. A temperature-programmed reduction (TPR) study evidenced the promoting effect of rhodium on the reducibility of CeO2 and showed that quasi-stoichiometric incorporation of chloride ions into ceria occurred at a relatively low reduction temperature (323–523 K), simultaneously with rhodium reduction to Rh(0). It is proposed that chloride incorporation occurs through the migration of surface Cl− ions into oxygen vacancies of CeO2 resulting from the reduction of surface oxygen by dissociated hydrogen spilled over from Rh(0) to the CeO2 surface. The incorporation of chloride was found to inhibit progressively the process of hydrogen spillover below 773 K. No CeOCl phase could be detected at the corresponding low reduction temperatures. However, catalysts containing higher chloride loadings were used to show that CeOCl was formed at higher reduction temperatures than that necessary for chloride incorporation into CeO2, supporting the hypothesis that Cl− ions are incorporated into the ceria lattice at low temperatures. CeOCl was found to be unstable in air but the phase could be restored upon additional reducing treatment, thus showing the reversibility of the Cl− ion migration into the oxygen vacancies of ceria.
{"title":"Ceria lattice oxygen ion substitution by Cl− during the reduction of Rh(Cl)/CeO2 catalysts. Formation and stability of CeOCl","authors":"F. Fajardie, ois Tempere, J. Manoli, G. Djéga-Mariadassou, G. Blanchard","doi":"10.1039/A805625K","DOIUrl":"https://doi.org/10.1039/A805625K","url":null,"abstract":"Rh/CeO2 systems prepared by anionic exchange of anionic rhodium chloro complexes contain significant amounts of chloride. They are referred to as Rh(Cl)/CeO2 catalysts. Reduction at 1173 K does not decrease the chloride content of these catalysts but calcination in air at the same temperature leads to total elimination of Cl− ions. A temperature-programmed reduction (TPR) study evidenced the promoting effect of rhodium on the reducibility of CeO2 and showed that quasi-stoichiometric incorporation of chloride ions into ceria occurred at a relatively low reduction temperature (323–523 K), simultaneously with rhodium reduction to Rh(0). It is proposed that chloride incorporation occurs through the migration of surface Cl− ions into oxygen vacancies of CeO2 resulting from the reduction of surface oxygen by dissociated hydrogen spilled over from Rh(0) to the CeO2 surface. The incorporation of chloride was found to inhibit progressively the process of hydrogen spillover below 773 K. No CeOCl phase could be detected at the corresponding low reduction temperatures. However, catalysts containing higher chloride loadings were used to show that CeOCl was formed at higher reduction temperatures than that necessary for chloride incorporation into CeO2, supporting the hypothesis that Cl− ions are incorporated into the ceria lattice at low temperatures. CeOCl was found to be unstable in air but the phase could be restored upon additional reducing treatment, thus showing the reversibility of the Cl− ion migration into the oxygen vacancies of ceria.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"21 1","pages":"3727-3735"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83989153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Brzeziński, Bartosz Różalski, G. Schroeder, F. Bartl, G. Zundel
Complexes of tributyl phosphate (TBPO) and tris(10-chloro-3,6,9-trioxadecyl) phosphate (TODPO) with HAuCl4 and their hydrates with various amounts of water were studied by FT-IR spectroscopy. TBPO with HAuCl4 forms homoconjugated PO+H···OP ⇌ PO···H+OP hydrogen bonds with large proton polarizability. In hydrates of homoconjugated PO+H···OP ⇌ PO···H+OP complexes, H5O2+ is formed with a hydrogen bond having large proton polarizability. In the 1:1 mixture no H3O+, but both H5O2+ and PO+H···OP ⇌ PO···H+OP homoconjugated bonds are present in the a 1:1 ratio. In the protonated and hydrated mixtures of TODPO no homoconjugated PO+H···OP ⇌ PO···H+OP hydrogen bonds and no H5O2+ species are found. In these complexes the proton and water molecules are present in the channels which show large proton polarizability. The behaviour of these protonated and hydrated channels is discussed with respect to the behaviour of the gramicidin channel.
{"title":"Excess proton hydrate structures with large proton polarizability in the channel of trioxaalkyl phosphate","authors":"B. Brzeziński, Bartosz Różalski, G. Schroeder, F. Bartl, G. Zundel","doi":"10.1039/A708928G","DOIUrl":"https://doi.org/10.1039/A708928G","url":null,"abstract":"Complexes of tributyl phosphate (TBPO) and tris(10-chloro-3,6,9-trioxadecyl) phosphate (TODPO) with HAuCl4 and their hydrates with various amounts of water were studied by FT-IR spectroscopy. TBPO with HAuCl4 forms homoconjugated PO+H···OP ⇌ PO···H+OP hydrogen bonds with large proton polarizability. In hydrates of homoconjugated PO+H···OP ⇌ PO···H+OP complexes, H5O2+ is formed with a hydrogen bond having large proton polarizability. In the 1:1 mixture no H3O+, but both H5O2+ and PO+H···OP ⇌ PO···H+OP homoconjugated bonds are present in the a 1:1 ratio. In the protonated and hydrated mixtures of TODPO no homoconjugated PO+H···OP ⇌ PO···H+OP hydrogen bonds and no H5O2+ species are found. In these complexes the proton and water molecules are present in the channels which show large proton polarizability. The behaviour of these protonated and hydrated channels is discussed with respect to the behaviour of the gramicidin channel.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"145 1","pages":"2093-2096"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86599867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two new algorithms have been developed for the deconvolution of nucleation and growth rates from electrochemical current–time transients. The first is called Bootstrap, and is based on the method of successive approximations. The second is called Simplefit, and utilizes a curve-fitting procedure based on the simplex method. Both are able to provide numerical estimates of the number of crystals as a function of time, to better than 2% accuracy, in the presence of significant noise. The advantage of the algorithms is that they produce accurate output under conditions where standard methods fail. In particular, the number of crystals versus time can be determined even when crystal growth switches from interfacial control to diffusion control on the timescale of measurements. The efficacy of the algorithms is demonstrated on two real systems, namely the nucleation of zinc on carbon, and the nucleation of lead on carbon. In both cases non-steady states of nucleation are readily observed in the presence of time-varying crystal growth rates. In addition, a new phenomenon is seen for which the name ''nucleation persistence'' is suggested. This is the transient continuation of a high rate of nucleation after a rapid decrease in overpotential. The phenomenon is attributed to the slow readjustment of the size distribution of microscopic nuclei on the electrode surface. Interestingly, the existence of nucleation persistence invalidates the double potential step technique, which has previously been regarded as the standard method for observing electrochemical nucleation and growth. Finally, the mathematical theory of nucleation persistence is briefly sketched.
{"title":"The deconvolution of nucleation and growth rates from electrochemical current–time transients","authors":"R. Deutscher, S. Fletcher","doi":"10.1039/A806348F","DOIUrl":"https://doi.org/10.1039/A806348F","url":null,"abstract":"Two new algorithms have been developed for the deconvolution of nucleation and growth rates from electrochemical current–time transients. The first is called Bootstrap, and is based on the method of successive approximations. The second is called Simplefit, and utilizes a curve-fitting procedure based on the simplex method. Both are able to provide numerical estimates of the number of crystals as a function of time, to better than 2% accuracy, in the presence of significant noise. The advantage of the algorithms is that they produce accurate output under conditions where standard methods fail. In particular, the number of crystals versus time can be determined even when crystal growth switches from interfacial control to diffusion control on the timescale of measurements. The efficacy of the algorithms is demonstrated on two real systems, namely the nucleation of zinc on carbon, and the nucleation of lead on carbon. In both cases non-steady states of nucleation are readily observed in the presence of time-varying crystal growth rates. In addition, a new phenomenon is seen for which the name ''nucleation persistence'' is suggested. This is the transient continuation of a high rate of nucleation after a rapid decrease in overpotential. The phenomenon is attributed to the slow readjustment of the size distribution of microscopic nuclei on the electrode surface. Interestingly, the existence of nucleation persistence invalidates the double potential step technique, which has previously been regarded as the standard method for observing electrochemical nucleation and growth. Finally, the mathematical theory of nucleation persistence is briefly sketched.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"23 1","pages":"3527-3536"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90353463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
[Ru3(CO)12] guests in Na56Y were thermally activated from 298 to 363 K, in a hydrogen atmosphere, generating intrazeolitic [H4Ru4(CO)12]. Hexaammineruthenium(III) complexes in Na56X have been thermally activated progressively from 298 to 393 K, in CO and H2 atmospheres. The generation process is via conversion of the intermediate [Ru(NH3)5(CO)]2+, RuI(CO)3 to [Ru6(CO)18]2−. The characterization of the structure and properties of these samples used a multi-analytical approach based on FTIR, UV-VIS, EXAFS spectroscopies and CO and H2 gas chemisorption. The research encompassed several key points as follows: (i) kinetics of the intrazeolitic diffusion of [Ru3(CO)12] clusters; (ii) oxidation fragmentation under O2 atmosphere and reductive regeneration under CO and H2 chemisorption with temperature-programmed heating for the intrazeolite anchoring of [Ru6(CO)18]2−; (iii) internal vs. external confinement of ruthenium carbonyl clusters; (iv) intrazeolite anchoring of ruthenium carbonyl clusters shows a strong reaction with the extraframework Na+ α-cage cations, through involvement of the oxygen end of the bridging or equatorial terminal carbonyl ligands; (v) comparison of orbitally degenerate ground-state for free Ru carbonyl clusters vs. the intrazeolitic anchoring site provides a theoretical indication of the symmetry distortion.These multi-analytical spectroscopic methods should motivate both new and established scientists to study further the anchoring of metal carbonyl clusters with other types of zeolite (such as ZSM-5 or MCM-41). Faujasite mediated synthesis of metal carbonyl clusters can provide routes to compounds which are not accessible by conventional solution techniques. Further, higher yield clusters, as well as a better understanding of the nucleation process of cluster formation and of the resulting chemical properties can be expected.
{"title":"Comprehensive structural and spectroscopic study of intrazeolite anchoring of ruthenium carbonyl clusters","authors":"G. Shen, A. Liu, M. Ichikawa","doi":"10.1039/A707777G","DOIUrl":"https://doi.org/10.1039/A707777G","url":null,"abstract":"[Ru3(CO)12] guests in Na56Y were thermally activated from 298 to 363 K, in a hydrogen atmosphere, generating intrazeolitic [H4Ru4(CO)12]. Hexaammineruthenium(III) complexes in Na56X have been thermally activated progressively from 298 to 393 K, in CO and H2 atmospheres. The generation process is via conversion of the intermediate [Ru(NH3)5(CO)]2+, RuI(CO)3 to [Ru6(CO)18]2−. The characterization of the structure and properties of these samples used a multi-analytical approach based on FTIR, UV-VIS, EXAFS spectroscopies and CO and H2 gas chemisorption. The research encompassed several key points as follows: (i) kinetics of the intrazeolitic diffusion of [Ru3(CO)12] clusters; (ii) oxidation fragmentation under O2 atmosphere and reductive regeneration under CO and H2 chemisorption with temperature-programmed heating for the intrazeolite anchoring of [Ru6(CO)18]2−; (iii) internal vs. external confinement of ruthenium carbonyl clusters; (iv) intrazeolite anchoring of ruthenium carbonyl clusters shows a strong reaction with the extraframework Na+ α-cage cations, through involvement of the oxygen end of the bridging or equatorial terminal carbonyl ligands; (v) comparison of orbitally degenerate ground-state for free Ru carbonyl clusters vs. the intrazeolitic anchoring site provides a theoretical indication of the symmetry distortion.These multi-analytical spectroscopic methods should motivate both new and established scientists to study further the anchoring of metal carbonyl clusters with other types of zeolite (such as ZSM-5 or MCM-41). Faujasite mediated synthesis of metal carbonyl clusters can provide routes to compounds which are not accessible by conventional solution techniques. Further, higher yield clusters, as well as a better understanding of the nucleation process of cluster formation and of the resulting chemical properties can be expected.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"94 1","pages":"1353-1362"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79589508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The 13C NMR spectra of organic electrolyte solutions containing 1 mol dm-3 LiPF6 in the three binary mixed solvent systems, methyl propionate (MP)–ethyl methyl carbonate (EMC), N,N-dimethylacetamide (DMA)–propylene carbonate (PC) and MP–ethyl propionate (EP) were measured at various solvent compositions. The difference in the chemical shifts of a solvent with and without the electrolyte was attributed to the coordination of the solvent to the lithium ion. The order of the normalized coordination shift which represents the coordinating ability for each mixed solvent system was MP>EMC, DMA>PC and MP>EP. An equation was derived which estimates the solvent ratio in the first coordination shell of the lithium ion in the binary mixed solvents for any solvent composition. The estimated ratio at a 1:1 volume composition was 1.6 for MP–EMC, 15 for DMA–PC and 1.3 for MP–EP.
{"title":"13 C NMR estimation of preferential solvation of lithium ions in non-aqueous mixed solvents","authors":"K. Matsubara, Rie Kaneuchi, Noriko Maekita","doi":"10.1039/A807010E","DOIUrl":"https://doi.org/10.1039/A807010E","url":null,"abstract":"The 13C NMR spectra of organic electrolyte solutions containing 1 mol dm-3 LiPF6 in the three binary mixed solvent systems, methyl propionate (MP)–ethyl methyl carbonate (EMC), N,N-dimethylacetamide (DMA)–propylene carbonate (PC) and MP–ethyl propionate (EP) were measured at various solvent compositions. The difference in the chemical shifts of a solvent with and without the electrolyte was attributed to the coordination of the solvent to the lithium ion. The order of the normalized coordination shift which represents the coordinating ability for each mixed solvent system was MP>EMC, DMA>PC and MP>EP. An equation was derived which estimates the solvent ratio in the first coordination shell of the lithium ion in the binary mixed solvents for any solvent composition. The estimated ratio at a 1:1 volume composition was 1.6 for MP–EMC, 15 for DMA–PC and 1.3 for MP–EP.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"36 1","pages":"3601-3605"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81207204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Interaction between Rose Bengal (RB) and an iron arene complex [Irg(+)] was studied by steady state and laser flash photolysis experiments. The contribution of static fluorescence quenching is evidenced by time resolved fluorescence experiments and can be explained by the occurrence of a ground state complex between RB and Irg(+). After light absorption by RB, the singlet state of RB is intercepted within the RB/Irg(+) pair, leading to semi-oxidised RB and a 19e iron arene complex.
{"title":"Laser flash photolysis studies of the interaction of Rose Bengal with an iron arene complex","authors":"D. Burget, J. Fouassier","doi":"10.1039/A801981I","DOIUrl":"https://doi.org/10.1039/A801981I","url":null,"abstract":"Interaction between Rose Bengal (RB) and an iron arene complex [Irg(+)] was studied by steady state and laser flash photolysis experiments. The contribution of static fluorescence quenching is evidenced by time resolved fluorescence experiments and can be explained by the occurrence of a ground state complex between RB and Irg(+). After light absorption by RB, the singlet state of RB is intercepted within the RB/Irg(+) pair, leading to semi-oxidised RB and a 19e iron arene complex.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"1 1","pages":"1849-1854"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87343060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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