A Kinetic study of the very low pressure thermolysis of phenylacetic acid above 900 K reveals that its decomposition occurs in a concerted manner, yielding toluene and carbon dioxide, probably via a four-centre transition state [reaction (1)] [graphic omitted] with log[k_∞(1)/s^(–1)]=[(13 ± 0.3)–(12 200 ± 500)]/T.
{"title":"Very low pressure pyrolysis of phenylacetic acid","authors":"A. Colussi, V. Amorebieta, M. A. Grela","doi":"10.1039/FT9928802125","DOIUrl":"https://doi.org/10.1039/FT9928802125","url":null,"abstract":"A Kinetic study of the very low pressure thermolysis of phenylacetic acid above 900 K reveals that its decomposition occurs in a concerted manner, yielding toluene and carbon dioxide, probably via a four-centre transition state [reaction (1)] [graphic omitted] with log[k_∞(1)/s^(–1)]=[(13 ± 0.3)–(12 200 ± 500)]/T.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"1 1","pages":"2125-2127"},"PeriodicalIF":0.0,"publicationDate":"2010-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90209748","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}
M. Neumann, M. Gehlen, M. Encinas, N. Allen, T. Corrales, C. Peinado, F. Catalina
The photophysics and the interaction of the excited states of substituted thioxanthones have been studied in order to be able to predict their behaviour as photoinitiators in photopolymerization systems. Electron-donor groups in position 2 in the thioxanthone ring lead to high fluorescence quantum yields, red-shifts in the emission spectra and long singlet lifetimes, explained by the separation of the nπ* and ππ* excited states induced by the higher electron density of the aromatic system. For some of the derivatives a biexponential decay due to slow relaxation of the solvent has been observed. Rate constants for the quenching of the singlet state by amines are near the diffusional limit and are not modified by substituents. On the other hand, substitution of electron-donor groups on the thioxanthone ring in position 2 decreases the triplet reactivity towards amines and alkenes. The incorporation of double bonds on the side chains of the compounds does not affect the lifetimes and reactivity of the thioxanthones.
{"title":"Photophysics and photoreactivity of substituted thioxanthones","authors":"M. Neumann, M. Gehlen, M. Encinas, N. Allen, T. Corrales, C. Peinado, F. Catalina","doi":"10.1039/A607264J","DOIUrl":"https://doi.org/10.1039/A607264J","url":null,"abstract":"The photophysics and the interaction of the excited states of \u0000substituted thioxanthones have been studied in order to be able to \u0000predict their behaviour as photoinitiators in photopolymerization \u0000systems. Electron-donor groups in position 2 in the thioxanthone ring \u0000lead to high fluorescence quantum yields, red-shifts in the emission \u0000spectra and long singlet lifetimes, explained by the separation of the \u0000nπ* and ππ* excited states induced by the higher electron \u0000density of the aromatic system. For some of the derivatives a \u0000biexponential decay due to slow relaxation of the solvent has been \u0000observed. Rate constants for the quenching of the singlet state by \u0000amines are near the diffusional limit and are not modified by \u0000substituents. On the other hand, substitution of electron-donor groups \u0000on the thioxanthone ring in position 2 decreases the triplet \u0000reactivity towards amines and alkenes. The incorporation of double \u0000bonds on the side chains of the compounds does not affect the \u0000lifetimes and reactivity of the thioxanthones.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"27 1","pages":"1517-1521"},"PeriodicalIF":0.0,"publicationDate":"2010-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77546166","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}
M. Abraham, David V. Prior, R. A. Schulz, J. J. Morris, P. J. Taylor
Equilibrium constants for 1 : 1 hydrogen bond complexation between 3,5-dichioropheno' (DCP) and 17 ketones and 12 ethers in cyclohexane solution have been obtained by an FTIR method that takes into account both diiaerization of the acid and formation of 2 :1 complexes. Enthalpies of complexation for the same ketones and ethers have been determined by a calorimeiric method, leading to values of log K, AG, AH and AS0 for 1 :1 complexation in the 29 systems, as well as log K2 for the 2 :1 complexation between 2 mol of acid and 1 mol of base. For the ketone systems there is very little variation in the three thermodynamic parameters with alkyl substitution, but for the ethers there are systematic variations depending on the alkyl substituent or if the ethers are cyclic. Values of the OH stretching frequency in the DCP complexes with the ketones and ethers in cyclohexane have been obtained. The band shapes for the DCP-ketone complexes are very asymmetric, possibly due to the presence of stereoisomeric complexes, but the VOH band for DCP-ether complexes is symmetric and very suitable for the evaluation of any relationship between v()H and A/f. It is found that for the complexation of DCP with the 12 aliphatic ethers in cyclohexane, there is almost no connection between the calorimetrically determined AH° values and values of AvOH.
{"title":"Hydrogen bonding Part 44 Thermodynamics of complexation of 3,5-dichlorophenol with ketones and ethers in cyclohexane: the Badger–Bauer relationship","authors":"M. Abraham, David V. Prior, R. A. Schulz, J. J. Morris, P. J. Taylor","doi":"10.1039/A708362I","DOIUrl":"https://doi.org/10.1039/A708362I","url":null,"abstract":"Equilibrium constants for 1 : 1 hydrogen bond complexation between 3,5-dichioropheno' (DCP) and 17 ketones and 12 ethers in cyclohexane solution have been obtained by an FTIR method that takes into account both diiaerization of the acid and formation of 2 :1 complexes. Enthalpies of complexation for the same ketones and ethers have been determined by a calorimeiric method, leading to values of log K, AG, AH and AS0 for 1 :1 complexation in the 29 systems, as well as log K2 for the 2 :1 complexation between 2 mol of acid and 1 mol of base. For the ketone systems there is very little variation in the three thermodynamic parameters with alkyl substitution, but for the ethers there are systematic variations depending on the alkyl substituent or if the ethers are cyclic. Values of the OH stretching frequency in the DCP complexes with the ketones and ethers in cyclohexane have been obtained. The band shapes for the DCP-ketone complexes are very asymmetric, possibly due to the presence of stereoisomeric complexes, but the VOH band for DCP-ether complexes is symmetric and very suitable for the evaluation of any relationship between v()H and A/f. It is found that for the complexation of DCP with the 12 aliphatic ethers in cyclohexane, there is almost no connection between the calorimetrically determined AH° values and values of AvOH.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"122 1","pages":"879-885"},"PeriodicalIF":0.0,"publicationDate":"1998-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76763188","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 application of small and weakly interacting probe molecules for the characterization of acidic and basic properties by FTIR spectroscopy is exemplified by using H- and alkali cation-exchanged zeolites as typical solid Bronsted and Lewis acids and Lewis bases. Criteria for the selection of probe molecules are given. Bronsted acidity can be characterized by the H-bonding method when CO and N2 are used as molecular probes. Quantum chemical calculations are shown to provide important additional information on the electronic nature of the adsorption interaction and the vibrational behaviour of the probe molecule. Lewis acidity dominates in cation-exchanged zeolites for small cations (Li+, Na+) whereas basic properties develop with increasing cation radius. CO, CO2, N2 and CH4 interact with cation centers, the interaction energy decreasing with increasing cation radius. CO at very low equilibrium pressures permits a siting of Na+, and the Al distribution in six-rings (SII-sites) can be probed. CH4 interacts with cations in the M+···H3CH configuration having C3v symmetry. CH-acids such as Cl3CH(D), acetylene and methylacetylene, are shown to be potentially suitable probe molecules for basic properties using the H-bonding method. All three molecules undergo Oz2−···H–C H-bonding and the induced red-shift of the C–H stretching frequency permits a ranking of the base strength of a given series of materials.
{"title":"IR spectroscopy of small and weakly interacting molecular probes for acidic and basic zeolites","authors":"H. Knözinger, S. Huber","doi":"10.1039/A802189I","DOIUrl":"https://doi.org/10.1039/A802189I","url":null,"abstract":"The application of small and weakly interacting probe molecules for the characterization of acidic and basic properties by FTIR spectroscopy is exemplified by using H- and alkali cation-exchanged zeolites as typical solid Bronsted and Lewis acids and Lewis bases. Criteria for the selection of probe molecules are given. Bronsted acidity can be characterized by the H-bonding method when CO and N2 are used as molecular probes. Quantum chemical calculations are shown to provide important additional information on the electronic nature of the adsorption interaction and the vibrational behaviour of the probe molecule. Lewis acidity dominates in cation-exchanged zeolites for small cations (Li+, Na+) whereas basic properties develop with increasing cation radius. CO, CO2, N2 and CH4 interact with cation centers, the interaction energy decreasing with increasing cation radius. CO at very low equilibrium pressures permits a siting of Na+, and the Al distribution in six-rings (SII-sites) can be probed. CH4 interacts with cations in the M+···H3CH configuration having C3v symmetry. CH-acids such as Cl3CH(D), acetylene and methylacetylene, are shown to be potentially suitable probe molecules for basic properties using the H-bonding method. All three molecules undergo Oz2−···H–C H-bonding and the induced red-shift of the C–H stretching frequency permits a ranking of the base strength of a given series of materials.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"6 1","pages":"2047-2059"},"PeriodicalIF":0.0,"publicationDate":"1998-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75056947","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}
Thermal electron transfer in protein structures is discussed on the basis of a model first proposed by R. A. Marcus. The electronic matrix element H12 is obtained in a many-electron theory for a number of typical structures of interest in proteins. Repetitive structures often permit resonance transfer over long distances provided the absolute value of the coupling matrix element between neighbouring atomic orbitals is larger than a critical value. The crucial energy separation Δ is obtained as a product of the transfer ‘pathway’ multiplied by coupling matrix elements at the gaps. It is shown that empty gaps are responsible for non-adiabatic behaviour and that saturated as well as aromatic parts of the protein permit electron transfer over larger distances than so far recognized. The Salemme model of the cytochrome c–cytochrome b5 interaction may permit electron transfer if the 8.4 A gap between the haem edges is filled by matter, for instance one of the propionate groups at the haem edge. Finally, the cytochrome c–cytochrome c peroxidase model of Poulos and Kraut is discussed and some alternative pathways suggested.
{"title":"Electron transfer in proteins","authors":"S. Larsson","doi":"10.1039/F29837901375","DOIUrl":"https://doi.org/10.1039/F29837901375","url":null,"abstract":"Thermal electron transfer in protein structures is discussed on the basis of a model first proposed by R. A. Marcus. The electronic matrix element H12 is obtained in a many-electron theory for a number of typical structures of interest in proteins. Repetitive structures often permit resonance transfer over long distances provided the absolute value of the coupling matrix element between neighbouring atomic orbitals is larger than a critical value. The crucial energy separation Δ is obtained as a product of the transfer ‘pathway’ multiplied by coupling matrix elements at the gaps. It is shown that empty gaps are responsible for non-adiabatic behaviour and that saturated as well as aromatic parts of the protein permit electron transfer over larger distances than so far recognized. The Salemme model of the cytochrome c–cytochrome b5 interaction may permit electron transfer if the 8.4 A gap between the haem edges is filled by matter, for instance one of the propionate groups at the haem edge. Finally, the cytochrome c–cytochrome c peroxidase model of Poulos and Kraut is discussed and some alternative pathways suggested.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"13 1","pages":"1375-1388"},"PeriodicalIF":0.0,"publicationDate":"1998-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79064302","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}
M. J. Blandamer, B. Briggs, P. Cullis, Keith D. Irlam, J. Engberts, J. Kevelam
Procedures are described for analysing enthalpograms characterising adsorption by macromolecules in solution recorded using a titration microcalorimeter. The experimental procedure involves injecting small aliquots of a solution containing adsorbate into a sample cell containing a solution of macromolecular adsorbent. Treatments based on both Langmuir and Frumkin adsorption isotherms are described. The procedures are illustrated by application of the derived equations to the interaction of micelles of sodium dodecylsulfate(aq) and of sodium decylsulfate(aq) with the water-soluble polymer, PVP. The dominant features in the recorded enthalpograms are described using equations developed from the Frumkin equation. In both cases the adsorption is endothermic attributed to hydrophobic interactions between polymer and surfactant. However, an important feature of the analysis is the characterisation of adsorbate–adsorbate interactions using enthalpic interaction parameters. The enthalpograms are characterised by three composition ranges: (i) micelle deaggregation and weak interaction of monomers with polymer, (ii) micelle adsorption on to the soluble polymer up to surface saturation and (iii) micelle dilution.
{"title":"Titration microcalorimetry of adsorption processes in aqueous systems","authors":"M. J. Blandamer, B. Briggs, P. Cullis, Keith D. Irlam, J. Engberts, J. Kevelam","doi":"10.1039/A704667G","DOIUrl":"https://doi.org/10.1039/A704667G","url":null,"abstract":"Procedures are described for analysing enthalpograms characterising adsorption by macromolecules in solution recorded using a titration microcalorimeter. The experimental procedure involves injecting small aliquots of a solution containing adsorbate into a sample cell containing a solution of macromolecular adsorbent. Treatments based on both Langmuir and Frumkin adsorption isotherms are described. The procedures are illustrated by application of the derived equations to the interaction of micelles of sodium dodecylsulfate(aq) and of sodium decylsulfate(aq) with the water-soluble polymer, PVP. The dominant features in the recorded enthalpograms are described using equations developed from the Frumkin equation. In both cases the adsorption is endothermic attributed to hydrophobic interactions between polymer and surfactant. However, an important feature of the analysis is the characterisation of adsorbate–adsorbate interactions using enthalpic interaction parameters. The enthalpograms are characterised by three composition ranges: (i) micelle deaggregation and weak interaction of monomers with polymer, (ii) micelle adsorption on to the soluble polymer up to surface saturation and (iii) micelle dilution.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"69 1","pages":"259-266"},"PeriodicalIF":0.0,"publicationDate":"1998-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78372702","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}
Six Na-saturated smectites were isolated from bentonites of various deposits. Their H-forms were prepared using H–OH–H resins. The interaction of methylene blue (MB) (0.05 mmol g-1) with Na-saturated untreated and H-autotransformed clay samples was investigated by the VIS spectroscopy of their dispersions. The spectra provided information about the formation of protonated dye cations, dimers, and higher agglomerates on the clay surface. The amounts of various dye forms were compared with the distributions of negative layer charge of the used clays, obtained by the alkylammonium method. Formation of MB dimers and higher agglomerates reflected sensitively the layer charge density of the smectites. MB cations formed predominantly higher agglomerates at the surface of those smectites with high charge density. Suppressed dye agglomeration was observed for the samples of lower layer charge density and was caused by greater distances between the adsorbed MB cations. Due to the high sensitivity of MB agglomeration on the layer charge and the simplicity of the method, MB–clay interaction can potentially be utilized for the layer charge characterization of smectites.
{"title":"Influence of the layer charge density of smectites on the interaction with methylene blue","authors":"J. Bujdák, M. Janek, J. Madejová, P. Komadel","doi":"10.1039/A805341C","DOIUrl":"https://doi.org/10.1039/A805341C","url":null,"abstract":"Six Na-saturated smectites were isolated from bentonites of various deposits. Their H-forms were prepared using H–OH–H resins. The interaction of methylene blue (MB) (0.05 mmol g-1) with Na-saturated untreated and H-autotransformed clay samples was investigated by the VIS spectroscopy of their dispersions. The spectra provided information about the formation of protonated dye cations, dimers, and higher agglomerates on the clay surface. The amounts of various dye forms were compared with the distributions of negative layer charge of the used clays, obtained by the alkylammonium method. Formation of MB dimers and higher agglomerates reflected sensitively the layer charge density of the smectites. MB cations formed predominantly higher agglomerates at the surface of those smectites with high charge density. Suppressed dye agglomeration was observed for the samples of lower layer charge density and was caused by greater distances between the adsorbed MB cations. Due to the high sensitivity of MB agglomeration on the layer charge and the simplicity of the method, MB–clay interaction can potentially be utilized for the layer charge characterization of smectites.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"51 1","pages":"3487-3492"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74037437","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. F. Namor, L. E. P. Salazar, M. A. L. Tanco, D. Kowalska, Jose A. Villanueva Salas, R. A. Schulz
A series of lithium and sodium ethyl p-tert-butylcalix(4)arene tetraethanoate and cryptand 222 salts has been isolated and thermochemically characterised in acetonitrile at 298.15 K. Also reported are the standard enthalpies of solution of common sodium salts (tetrafluoroborate, trifluoromethanesulfonate, iodide and bromide) in this solvent at the same temperature. Solution data for the free and the complexed salts and for the ligand are combined with complexation data for the appropriate cation and macrocycle in acetonitrile to derive the enthalpies of co-ordination of these systems for the process where the product and the reactants are in the solid state. Comparison of data involving lithium and the calix(4)arene ester and the cryptand 222 with those for crown ethers reflects considerable weakening of cation–anion interactions in the former ligands relative to crown ethers. It is concluded that for a given ligand and metal cation, the anion effect is reflected in the co-ordination enthalpies. On the other hand, for systems containing the same ligand and anion, there is a decrease in enthalpic stability in moving from lithium to sodium. The need to obtain experimental data on crystal lattice enthalpies of these ligands and their metal ion complex salts is emphasised.
{"title":"Solution and co-ordination enthalpies (solid state) of lithium and sodium macrocycle (ethyl p-tert-butylcalix(4)arene tetraethanoate, cryptand 222 and crown ethers) systems","authors":"A. F. Namor, L. E. P. Salazar, M. A. L. Tanco, D. Kowalska, Jose A. Villanueva Salas, R. A. Schulz","doi":"10.1039/A805190I","DOIUrl":"https://doi.org/10.1039/A805190I","url":null,"abstract":"A series of lithium and sodium ethyl p-tert-butylcalix(4)arene tetraethanoate and cryptand 222 salts has been isolated and thermochemically characterised in acetonitrile at 298.15 K. Also reported are the standard enthalpies of solution of common sodium salts (tetrafluoroborate, trifluoromethanesulfonate, iodide and bromide) in this solvent at the same temperature. Solution data for the free and the complexed salts and for the ligand are combined with complexation data for the appropriate cation and macrocycle in acetonitrile to derive the enthalpies of co-ordination of these systems for the process where the product and the reactants are in the solid state. Comparison of data involving lithium and the calix(4)arene ester and the cryptand 222 with those for crown ethers reflects considerable weakening of cation–anion interactions in the former ligands relative to crown ethers. It is concluded that for a given ligand and metal cation, the anion effect is reflected in the co-ordination enthalpies. On the other hand, for systems containing the same ligand and anion, there is a decrease in enthalpic stability in moving from lithium to sodium. The need to obtain experimental data on crystal lattice enthalpies of these ligands and their metal ion complex salts is emphasised.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"93 1","pages":"3111-3115"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75230306","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}
T. Takaishi, K. Tsutsumi, K. Chubachi, A. Matsumoto
Adsorption induced phase transitions of ZSM-5 by p-xylene, taking place between P21/n–Pnma and Pnma–P212121 phases, have been measured in the temperature range 298–352 K. Adsorption isotherms well obey the Langmuir equation. The differential heat of adsorption and difference in thermal entropies between adsorbate and gaseous molecules were determined to be 84 kJ mol-1 and -33 k in the Pnma phase and 80 kJ mol-1 and -31.6 k in the P21/n phase, respectively. Adsorption heats were calorimetrically measured as a function of adsorbed amounts at 298, 333 and 352 K. The heat curves have valleys relating to the phase transition, and their shapes are well explained by statistical thermodynamics. Dependences of the transition pressure upon temperature and types of exchangeable cation in ZSM-5 are quantitatively explained. Observed adsorption–desorption hysteresis was ascribed to a domain structure of the ZSM-5 crystal, but was not quantitatively analyzed.
{"title":"Adsorption induced phase transition of ZSM-5 by p-xylene","authors":"T. Takaishi, K. Tsutsumi, K. Chubachi, A. Matsumoto","doi":"10.1039/A705942F","DOIUrl":"https://doi.org/10.1039/A705942F","url":null,"abstract":"Adsorption induced phase transitions of ZSM-5 by p-xylene, taking place between P21/n–Pnma and Pnma–P212121 phases, have been measured in the temperature range 298–352 K. Adsorption isotherms well obey the Langmuir equation. The differential heat of adsorption and difference in thermal entropies between adsorbate and gaseous molecules were determined to be 84 kJ mol-1 and -33 k in the Pnma phase and 80 kJ mol-1 and -31.6 k in the P21/n phase, respectively. Adsorption heats were calorimetrically measured as a function of adsorbed amounts at 298, 333 and 352 K. The heat curves have valleys relating to the phase transition, and their shapes are well explained by statistical thermodynamics. Dependences of the transition pressure upon temperature and types of exchangeable cation in ZSM-5 are quantitatively explained. Observed adsorption–desorption hysteresis was ascribed to a domain structure of the ZSM-5 crystal, but was not quantitatively analyzed.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"24 1","pages":"601-608"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72980590","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}
Tadatake Sato, Kiyotaka Hori, M. Fujitsuka, A. Watanabe, O. Ito, Kazuyoshi Tanaka
The synthesis of three kinds of bis(2,2′-bithiophene-5-yl)benzenes (1,2-, 1,3- and 1,4-bis(2,2′-bithiophene-5-yl)benzene; o-PhBT2, m-PhBT2 and p-PhBT2) and analyses of their photophysical properties are reported. The electronic structures were also studied by the molecular orbital (MO) method. It was found that the extension of π-conjugation varies with the substitution mode (o-, m-, or p-), which in turn influences the absorption, fluorescence and transient absorption spectra. The unique behaviour of o-PhBT2 was interpreted in terms of its lowest unoccupied MO (LUMO) pattern, in which π-orbitals on the adjacent sulfur atoms in each bithienyl moiety can have considerable overlap.
{"title":"Photophysical properties of bis(2,2′-bithiophene-5-yl)benzenes","authors":"Tadatake Sato, Kiyotaka Hori, M. Fujitsuka, A. Watanabe, O. Ito, Kazuyoshi Tanaka","doi":"10.1039/A802514B","DOIUrl":"https://doi.org/10.1039/A802514B","url":null,"abstract":"The synthesis of three kinds of bis(2,2′-bithiophene-5-yl)benzenes (1,2-, 1,3- and 1,4-bis(2,2′-bithiophene-5-yl)benzene; o-PhBT2, m-PhBT2 and p-PhBT2) and analyses of their photophysical properties are reported. The electronic structures were also studied by the molecular orbital (MO) method. It was found that the extension of π-conjugation varies with the substitution mode (o-, m-, or p-), which in turn influences the absorption, fluorescence and transient absorption spectra. The unique behaviour of o-PhBT2 was interpreted in terms of its lowest unoccupied MO (LUMO) pattern, in which π-orbitals on the adjacent sulfur atoms in each bithienyl moiety can have considerable overlap.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"22 1","pages":"2355-2360"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73111185","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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