Alkali-metal ion transport by a series of p-tert-butylcalix[n]arene (n=4, 5, 6, 7, 8) esters (1–5) across a soybean phospholipid bilayer membrane has been investigated by a voltage clamp method. The measurement of electric currents resulting from ion transport across the phospholipid bilayer shows that esters 1–4, show ion transport ability but that 5 does not. From an analysis of current–voltage curves, the values of ion permeability across the bilayer are determined for 1–4. The ion permeability of Na+ by 1 is >20 times that of other alkali-metal ions, suggesting that 1 acts as a selective Na+ carrier in phospholipid bilayer membranes. 2 transports K+ better than Na+, while the ion transport selectivity of 2 is poor compared to that of 1. Both 3 and 4 shows Cs+ transport selectivity. The transport selectivity (Cs+/Rb+) of 3 is better than that of 4 by a factor of 2.
{"title":"Ion transport activity of calix[n]arene (n=4, 5, 6, 7, 8) esters toward alkali-metal cations in a phospholipid bilayer membrane","authors":"T. Jin, M. Kinjo, Yoko Kobayashi, H. Hirata","doi":"10.1039/A805101A","DOIUrl":"https://doi.org/10.1039/A805101A","url":null,"abstract":"Alkali-metal ion transport by a series of p-tert-butylcalix[n]arene (n=4, 5, 6, 7, 8) esters (1–5) across a soybean phospholipid bilayer membrane has been investigated by a voltage clamp method. The measurement of electric currents resulting from ion transport across the phospholipid bilayer shows that esters 1–4, show ion transport ability but that 5 does not. From an analysis of current–voltage curves, the values of ion permeability across the bilayer are determined for 1–4. The ion permeability of Na+ by 1 is >20 times that of other alkali-metal ions, suggesting that 1 acts as a selective Na+ carrier in phospholipid bilayer membranes. 2 transports K+ better than Na+, while the ion transport selectivity of 2 is poor compared to that of 1. Both 3 and 4 shows Cs+ transport selectivity. The transport selectivity (Cs+/Rb+) of 3 is better than that of 4 by a factor of 2.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"92 1","pages":"3135-3140"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80495327","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 high resolution Fourier transform spectrum of arsine was revisited in the region 4000–4350 cm-1 at a resolution of 0.006 cm-1. Altogether 189 energy levels of the local mode (110 A1/E) states were assigned by use of the ground state combination difference method. The vibration–rotation parameters were obtained from a weighted non-linear least-squares fit and discussed in the local mode model.
{"title":"High resolution vibration–rotation spectra of the arsine local mode (110 A1/E) band","authors":"Shengfu Yang, Hai Lin, Doug Wang, Qing-shi Zhu","doi":"10.1039/A708723C","DOIUrl":"https://doi.org/10.1039/A708723C","url":null,"abstract":"The high resolution Fourier transform spectrum of arsine was revisited in the region 4000–4350 cm-1 at a resolution of 0.006 cm-1. Altogether 189 energy levels of the local mode (110 A1/E) states were assigned by use of the ground state combination difference method. The vibration–rotation parameters were obtained from a weighted non-linear least-squares fit and discussed in the local mode model.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"19 1","pages":"1397-1401"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81569823","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 proton affinities PA(B) of the four oxygen lone pairs and of the two nitrogen atoms and the deprotonation energies PA(A-) of the two NH bonds of uracil are calculated by density functional theory (DFT) using the 6-31G(d,p) and 6-31G++(d,p) basis set. The PAs are also calculated by abinitio MO theory (MP4) using 6-31G(d,p) for comparison. The DFT/B3LYP energies and the frequency shifts of the ν(OH) stretching vibrations are calculated with the 6-31++G(d,p) basis for the three cyclic structures of the uracil–water complexes. The usual correlations between energies of frequency shifts and the PAs do not hold in the case of closed structures. The most stable cyclic complex is formed at the oxygen lone pair characterized by the lowest basicity and at the NH bond characterized by the highest acidity. The energy of the complex decreases with increasing value of the difference PA(A-)-PA(B).
{"title":"Protonation and deprotonation energies of uracil Implications for the uracil–water complex","authors":"M. Nguyen, A. K. Chandra","doi":"10.1039/A708804C","DOIUrl":"https://doi.org/10.1039/A708804C","url":null,"abstract":"The proton affinities PA(B) of the four oxygen lone pairs and of the two nitrogen atoms and the deprotonation energies PA(A-) of the two NH bonds of uracil are calculated by density functional theory (DFT) using the 6-31G(d,p) and 6-31G++(d,p) basis set. The PAs are also calculated by abinitio MO theory (MP4) using 6-31G(d,p) for comparison. The DFT/B3LYP energies and the frequency shifts of the ν(OH) stretching vibrations are calculated with the 6-31++G(d,p) basis for the three cyclic structures of the uracil–water complexes. The usual correlations between energies of frequency shifts and the PAs do not hold in the case of closed structures. The most stable cyclic complex is formed at the oxygen lone pair characterized by the lowest basicity and at the NH bond characterized by the highest acidity. The energy of the complex decreases with increasing value of the difference PA(A-)-PA(B).","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"81 1","pages":"1277-1280"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84204920","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. Roux, Pilar Jime′nez, J. Dávalos, C. Turrión, H. Afeefy, J. Liebman
The relative stabilities of the isomeric dimethyl benzenedicarboxylates have been studied by a thermochemical investigation of dimethyl phthalate, dimethyl isophthalate and dimethyl terephthalate. The enthalpies of formation in the condensed state for dimethyl phthalate and dimethyl isophthalate, determined from combustion calorimetry measurements, are -683.8±2.7 and -730.1±2.0 kJ mol-1, respectively. The enthalpies of sublimation for dimethyl isophthalate and dimethyl terephthalate, determined by the Knudsen effusion technique are 100.9±0.2 and 104.6±0.3 kJ mol-1, respectively. From the above results and the value of the enthalpy of formation in the condensed state of dimethyl terephthalate, previously determined in our laboratory, and the value of the enthalpy of vaporization of dimethyl phthalate taken from the literature, the enthalpies of formation in the gaseous state at 298.15 K for the ortho-, meta- and para-isomers of dimethyl benzenedicarboxylates are found to be -606.1, -629.2±2.0 and -628.0±1.0 kJ mol-1, respectively. The relative stabilities of the isomeric dimethyl benzenedicarboxylates, isomeric dicyanobenzenes and dinitrobenzenes are compared.
{"title":"Enthalpies of formation of methyl benzenecarboxylates","authors":"M. Roux, Pilar Jime′nez, J. Dávalos, C. Turrión, H. Afeefy, J. Liebman","doi":"10.1039/A800401C","DOIUrl":"https://doi.org/10.1039/A800401C","url":null,"abstract":"The relative stabilities of the isomeric dimethyl benzenedicarboxylates have been studied by a thermochemical investigation of dimethyl phthalate, dimethyl isophthalate and dimethyl terephthalate. The enthalpies of formation in the condensed state for dimethyl phthalate and dimethyl isophthalate, determined from combustion calorimetry measurements, are -683.8±2.7 and -730.1±2.0 kJ mol-1, respectively. The enthalpies of sublimation for dimethyl isophthalate and dimethyl terephthalate, determined by the Knudsen effusion technique are 100.9±0.2 and 104.6±0.3 kJ mol-1, respectively. From the above results and the value of the enthalpy of formation in the condensed state of dimethyl terephthalate, previously determined in our laboratory, and the value of the enthalpy of vaporization of dimethyl phthalate taken from the literature, the enthalpies of formation in the gaseous state at 298.15 K for the ortho-, meta- and para-isomers of dimethyl benzenedicarboxylates are found to be -606.1, -629.2±2.0 and -628.0±1.0 kJ mol-1, respectively. The relative stabilities of the isomeric dimethyl benzenedicarboxylates, isomeric dicyanobenzenes and dinitrobenzenes are compared.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"116 7 1","pages":"887-890"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84237289","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}
Electropolymerisation of the 5-substituted indole monomers, 5-cyanoindole, indole-5-carboxylic acid, 5-chloroindole, 5-bromoindole and 5-methoxyindole results in a redox-active film consisting of a cyclic trimer and chains of linked cyclic trimer (polymer). The monomer, trimer and polymer species are fluorescent and have been studied using steady state fluorescence spectroscopy in solution at room temperature. The excitation and emission spectra of the trimer species show a significant shift to longer wavelength compared to the monomer, consistent with the greater extent of electron delocalisation. The emission properties of the 5-substituted indole monomers are very dependent upon solvent polarity and the nature of the 5-substituent; in contrast, the trimer species show little dependence. Controlling the electrochemical conditions allows variation of the relative proportions of trimer and polymer species. The excitation and emission spectra of the polymer species are shifted to longer wavelength, are broader and are of lower intensity than those of the trimer.
{"title":"Fluorescence properties of electropolymerised 5-substituted indoles in solution","authors":"P. Jennings, Anita C Jones, A. Mount","doi":"10.1039/A806721J","DOIUrl":"https://doi.org/10.1039/A806721J","url":null,"abstract":"Electropolymerisation of the 5-substituted indole monomers, 5-cyanoindole, indole-5-carboxylic acid, 5-chloroindole, 5-bromoindole and 5-methoxyindole results in a redox-active film consisting of a cyclic trimer and chains of linked cyclic trimer (polymer). The monomer, trimer and polymer species are fluorescent and have been studied using steady state fluorescence spectroscopy in solution at room temperature. The excitation and emission spectra of the trimer species show a significant shift to longer wavelength compared to the monomer, consistent with the greater extent of electron delocalisation. The emission properties of the 5-substituted indole monomers are very dependent upon solvent polarity and the nature of the 5-substituent; in contrast, the trimer species show little dependence. Controlling the electrochemical conditions allows variation of the relative proportions of trimer and polymer species. The excitation and emission spectra of the polymer species are shifted to longer wavelength, are broader and are of lower intensity than those of the trimer.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"149 1","pages":"3619-3624"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84240778","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 dielectric spectra and thermodynamics of macromolecular growth in the diepoxide–diamine liquid mixtures have been studied simultaneously, and in real time, as the original molecular liquid transformed to a rigid state of a vitrified network structure. Both stoichiometric and the excess amine compositions were studied and the dielectric properties of their final polymerized state investigated. The rate of polymerization is remarkably increased in the diamine-rich composition, and vitrification occurs sooner. A change in the rate of heat release profile is attributed to the onset of another reaction at longer times, which does not require the diamine. The dc conductivity, σ0, decreases progressively more rapidly during the initial stage of polymerization, producing a sigmoid shape when it is plotted against time. This shape is stretched out when plots are made against the number of covalent bonds formed. For a fixed number of covalent bonds, n, formed at 324.5 K, the relaxation time, τ0, for the diamine-rich composition is twice that of the stoichiometric composition. Interpretation in terms of the configurational entropy theory shows that this is due to the lowering of vibrational frequencies. The stretched exponential relaxation parameter. β, increases from 0.25 for the stoichiometric to 0.36 for the diamine-rich composition. The product, τ0σ0, increases with increase in n, thus showing that τ0 and σ0 are not inversely related, and that requires consideration of other mechanisms for dc conduction. A faster dipolar reorientation dynamics evolves on polymerization and, in the fully polymerized state of the amine-rich composition, its peak shifts to a lower frequency.
{"title":"Real time dielectric spectroscopy and bond connectivity during polymerization of stoichiometric and amine-rich, diepoxide–diamine compositions","authors":"C. Ferrari, E. Tombari, G. Salvetti, G. P. Johari","doi":"10.1039/A800277K","DOIUrl":"https://doi.org/10.1039/A800277K","url":null,"abstract":"The dielectric spectra and thermodynamics of macromolecular growth in the diepoxide–diamine liquid mixtures have been studied simultaneously, and in real time, as the original molecular liquid transformed to a rigid state of a vitrified network structure. Both stoichiometric and the excess amine compositions were studied and the dielectric properties of their final polymerized state investigated. The rate of polymerization is remarkably increased in the diamine-rich composition, and vitrification occurs sooner. A change in the rate of heat release profile is attributed to the onset of another reaction at longer times, which does not require the diamine. The dc conductivity, σ0, decreases progressively more rapidly during the initial stage of polymerization, producing a sigmoid shape when it is plotted against time. This shape is stretched out when plots are made against the number of covalent bonds formed. For a fixed number of covalent bonds, n, formed at 324.5 K, the relaxation time, τ0, for the diamine-rich composition is twice that of the stoichiometric composition. Interpretation in terms of the configurational entropy theory shows that this is due to the lowering of vibrational frequencies. The stretched exponential relaxation parameter. β, increases from 0.25 for the stoichiometric to 0.36 for the diamine-rich composition. The product, τ0σ0, increases with increase in n, thus showing that τ0 and σ0 are not inversely related, and that requires consideration of other mechanisms for dc conduction. A faster dipolar reorientation dynamics evolves on polymerization and, in the fully polymerized state of the amine-rich composition, its peak shifts to a lower frequency.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"15 1","pages":"1293-1300"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84374691","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}
Solvent effects on triplet–triplet energy transfer (TET) from triplet benzophenone (3BP*) to naphthol (NpOH) competing with hydrogen atom abstraction (HA) of 3BP* from NpOH and methoxynaphthalene (NpOMe) without HA have been studied in fluid media by 355 nm laser flash photolysis at 295 K. The efficiency (ψTET) and rate constant (kTET) of TET in these systems were obtained. It was shown that the value of kTET was dependent not only on the solvent viscosity (η) but also on the dielectric constant (κ) of the solvents, and ψTET and kTET increased with increasing κ, contrary to the Dexter prediction. An increase in kTET with increasing κ may be caused by the contribution of the dipole–dipole interaction (by the Forster theory) due to perturbation of the 1(π, π*) state to the lowest triplet state 3(n, π*) of benzophenone, in addition to the electron-exchange mechanism (by the Dexter theory).
{"title":"Solvent dependence of triplet energy transfer from triplet benzophenone to naphthols and methoxynaphthalenes","authors":"T. Tanaka, M. Yamaji, H. Shizuka","doi":"10.1039/A707820J","DOIUrl":"https://doi.org/10.1039/A707820J","url":null,"abstract":"Solvent effects on triplet–triplet energy transfer (TET) from triplet benzophenone (3BP*) to naphthol (NpOH) competing with hydrogen atom abstraction (HA) of 3BP* from NpOH and methoxynaphthalene (NpOMe) without HA have been studied in fluid media by 355 nm laser flash photolysis at 295 K. The efficiency (ψTET) and rate constant (kTET) of TET in these systems were obtained. It was shown that the value of kTET was dependent not only on the solvent viscosity (η) but also on the dielectric constant (κ) of the solvents, and ψTET and kTET increased with increasing κ, contrary to the Dexter prediction. An increase in kTET with increasing κ may be caused by the contribution of the dipole–dipole interaction (by the Forster theory) due to perturbation of the 1(π, π*) state to the lowest triplet state 3(n, π*) of benzophenone, in addition to the electron-exchange mechanism (by the Dexter theory).","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"9 1","pages":"1179-1187"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84413352","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}
K. Hadjiivanov, M. Mihaylov, N. Abadjieva, D. Klissurski
Three Ni/TiO2 samples have been synthesized by impregnation (sample Ni-i-Ti), adsorption of Ni2+ ions from alkaline media on TiO2 (sample Ni-1-Ti) and on reduced Ni-1-Ti (sample Ni-2-Ti). The samples have been characterized by TPR, IR spectroscopy of adsorbed CO and X-ray diffraction. Impregnation leads to a less homogeneous distribution of the active phase and a negligibly lower temperature of reduction as compared with the adsorption technique. Reduction of Ni-i-Ti results in the formation of nickel particles with an average diameter of 22 nm. Surface N was detected by CO testing. The average diameter of the nickel particles in the reduced Ni-1-Ti sample is about 20 nm. In this case, however, no metal nickel was detected on the surface, i.e. the metal particles are encapsulated in the support. The majority of the active sites for adsorption are regenerated during the reduction of nickel in Ni-1-Ti, which allows Ni2+ ions to be adsorbed again on the sample. As a result, the nickel concentration increases. The mean diameter of the nickel particles on reduced Ni-2-Ti remains of the order of 20 nm, similar to the case of the reduced Ni-1-Ti sample. With Ni-2-Ti, however, surface metal nickel was detected by CO adsorption. It is concluded that successive absorption–reduction of Ni2+ ions might be used to prepare titania supported nickel catalyst with a desired nickel concentration and metal particles that are not encapsulated in the support. Some new aspects of the strong metal–support interaction (SMSI) mechanism are also discussed.
通过浸渍(Ni-i- ti样品)、碱性介质中Ni2+离子在TiO2 (Ni-1- ti样品)和还原Ni-1- ti (Ni-2- ti样品)上吸附制备了3种Ni/TiO2样品。用TPR、吸附CO的红外光谱和x射线衍射对样品进行了表征。与吸附技术相比，浸渍导致活性相分布不均匀，还原温度可忽略不计。Ni-i-Ti的还原形成了平均直径为22 nm的镍颗粒。用CO法测定表面氮。还原后的Ni-1-Ti样品中镍颗粒的平均直径约为20 nm。然而，在这种情况下，表面没有检测到金属镍，即金属颗粒被封装在支架中。在Ni-1-Ti中镍的还原过程中，大部分吸附活性位点得以再生，使得Ni2+离子再次吸附在样品上。结果，镍的浓度增加。还原后的Ni-2-Ti上镍颗粒的平均直径保持在20 nm左右，与还原后的Ni-1-Ti样品相似。而Ni-2-Ti则通过CO吸附法检测表面金属镍。结果表明，通过Ni2+离子的连续吸附还原，可以制备出具有理想镍浓度的二氧化钛负载型镍催化剂，并使金属颗粒不被包裹在载体中。本文还讨论了强金属-支撑相互作用(SMSI)机理的一些新方面。
{"title":"Characterization of Ni/TiO2 catalysts prepared by successive adsorption–reduction of Ni2+ ions","authors":"K. Hadjiivanov, M. Mihaylov, N. Abadjieva, D. Klissurski","doi":"10.1039/A804978E","DOIUrl":"https://doi.org/10.1039/A804978E","url":null,"abstract":"Three Ni/TiO2 samples have been synthesized by impregnation (sample Ni-i-Ti), adsorption of Ni2+ ions from alkaline media on TiO2 (sample Ni-1-Ti) and on reduced Ni-1-Ti (sample Ni-2-Ti). The samples have been characterized by TPR, IR spectroscopy of adsorbed CO and X-ray diffraction. Impregnation leads to a less homogeneous distribution of the active phase and a negligibly lower temperature of reduction as compared with the adsorption technique. Reduction of Ni-i-Ti results in the formation of nickel particles with an average diameter of 22 nm. Surface N was detected by CO testing. The average diameter of the nickel particles in the reduced Ni-1-Ti sample is about 20 nm. In this case, however, no metal nickel was detected on the surface, i.e. the metal particles are encapsulated in the support. The majority of the active sites for adsorption are regenerated during the reduction of nickel in Ni-1-Ti, which allows Ni2+ ions to be adsorbed again on the sample. As a result, the nickel concentration increases. The mean diameter of the nickel particles on reduced Ni-2-Ti remains of the order of 20 nm, similar to the case of the reduced Ni-1-Ti sample. With Ni-2-Ti, however, surface metal nickel was detected by CO adsorption. It is concluded that successive absorption–reduction of Ni2+ ions might be used to prepare titania supported nickel catalyst with a desired nickel concentration and metal particles that are not encapsulated in the support. Some new aspects of the strong metal–support interaction (SMSI) mechanism are also discussed.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"11 1","pages":"3711-3716"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85954668","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}
Diamagnetic susceptibilities of two series of organic compounds have been described by using a novel sub-structural approach. The method is based on the calculation of spectral moments of the bond adjacency matrix of molecular graphs. These spectral moments are expressed via algebraic expressions as linear combinations of simple fragments present in molecules. Contributions of each fragment to the diamagnetic susceptibility of alkanes and alkyl halides were obtained by using this approach. Quantitative models found are significant from a statistical point of view and they permit a clear interpretation of the studied property in terms of the structural features of molecules.
{"title":"Modelling the diamagnetic susceptibility of organic compounds by a sub-structural graph-theoretical approach","authors":"Ernesto Estrada","doi":"10.1039/A709032C","DOIUrl":"https://doi.org/10.1039/A709032C","url":null,"abstract":"Diamagnetic susceptibilities of two series of organic compounds have been described by using a novel sub-structural approach. The method is based on the calculation of spectral moments of the bond adjacency matrix of molecular graphs. These spectral moments are expressed via algebraic expressions as linear combinations of simple fragments present in molecules. Contributions of each fragment to the diamagnetic susceptibility of alkanes and alkyl halides were obtained by using this approach. Quantitative models found are significant from a statistical point of view and they permit a clear interpretation of the studied property in terms of the structural features of molecules.","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"334 1","pages":"1407-1410"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78588376","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 kinetics of the electron transfer self-exchange reaction [Fe3O(O2CCMe3)6(py)3]+ + [Fe3O(O2CCMe3)6(py)3] ⇄ [Fe3O(O2CCMe3)6(py)3] + [Fe3O(O2CCMe3)6(py)3]+ have been measured by NMR line broadening. Both reactants are paramagnetic and it was possible to measure broadening of lines of each component by exchange with the other. In dichloromethane at 23 °C the second-order rate constant is (3.7 ± 0.1) × 104M−1 s−1. The ligand exchange reactions of [Fe3O(O2CCMe3)6(py)3]n+ with pyridine are rapid for the mixed-valence complex (n = 0) but slow for the oxidised complex (n = 1).
{"title":"NMR study of electron transfer between paramagnetic complexes Kinetics of the self-exchange reaction [Fe3O(O2CCMe3)6(py)3]+/0 (py = pyridine)","authors":"F. E. Sowrey, C. Macdonald, R. D. Cannon","doi":"10.1039/A801051J","DOIUrl":"https://doi.org/10.1039/A801051J","url":null,"abstract":"The kinetics of the electron transfer self-exchange reaction [Fe3O(O2CCMe3)6(py)3]+ + [Fe3O(O2CCMe3)6(py)3] ⇄ [Fe3O(O2CCMe3)6(py)3] + [Fe3O(O2CCMe3)6(py)3]+ have been measured by NMR line broadening. Both reactants are paramagnetic and it was possible to measure broadening of lines of each component by exchange with the other. In dichloromethane at 23 °C the second-order rate constant is (3.7 ± 0.1) × 104M−1 s−1. The ligand exchange reactions of [Fe3O(O2CCMe3)6(py)3]n+ with pyridine are rapid for the mixed-valence complex (n = 0) but slow for the oxidised complex (n = 1).","PeriodicalId":17286,"journal":{"name":"Journal of the Chemical Society, Faraday Transactions","volume":"293 1","pages":"1571-1574"},"PeriodicalIF":0.0,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79541003","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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