Journal of The Chemical Society-dalton Transactions, 1994
The NMR and Mossbauer spectra and electrochemistry of the N-donor ferrocenyl ligands [Fe(η5-C5H5)... more The NMR and Mossbauer spectra and electrochemistry of the N-donor ferrocenyl ligands [Fe(η5-C5H5){(η5-C5H4CHNCH2Ph)}] and [Fe(η5-C5H5)(η5-C5H4CH2NMe2)] as well as their mononuclear derivatives with σ(Pd–Csp2, ferrocene) bonds [[graphic omitted]CH2Ph)}Cl(L)], [[graphic omitted]Me2)}Cl(L)][L = 1 -methylimidazole (mim) or PPh3], and [Pd{(η5-C5H5)Fe(η5-C5H3CH2NMe2)}Cl(PPh3)2] have been studied. Comparison of the data allows an understanding of the influence of the nature of the N-donor atom of the ferrocenyl moiety (sp2versus sp3) upon the properties of these compounds. In particular, the differences observed in the quadrupole splitting parameters obtained from Mossbauer spectroscopy reveal not only that the palladium(II) acts as an electron-withdrawing group in all these cyclometallated derivatives, but also that most of the electron density is withdrawn from the imine CHN moiety in the derivatives containing ferrocenyl Schiff bases as ligands. The crystal structures of [[graphic omitted]CH2Ph)}Cl(PPh3)] and [[graphic omitted]Me2)}Cl(mim)] have been determined.
Herein we describe the results of a study on the photoluminescence of cubic nanosized Y2O3:Tb. Th... more Herein we describe the results of a study on the photoluminescence of cubic nanosized Y2O3:Tb. These results confirm our earlier conclusions based on cathodoluminescence about the energy flow from excited Tb in a S6 lattice site to Tb in a C2 site.
Journal of the Chemical Society, Dalton Transactions, 1975
The ideal perovskite structure of CsSnIIBr3 at room temperature has been confirmed by a single-cr... more The ideal perovskite structure of CsSnIIBr3 at room temperature has been confirmed by a single-crystal X-ray diffraction study. It is proposed that the high-symmetry environment for the SnII in this compound arises because the distorting effect of the non-bonding electrons is reduced by their populating an empty low-energy band in the solid, thus giving rise to the black colour and metallic-conducting properties. The high-temperature phases of CsSn2IIBr5, Cs4SnIIBr6, and of compositions from the CsSnII2Br5–CsSnII2Cl5 system show similar properties. Colour can be introduced into the Cs2SnIVBr6 system by formation of mixed phases with CsSnIIBr3 which has a closely related structure. The colour and electrical properties of the mixed SnII–SnIV material can be explained by population of the low-energy delocalised solid-state bands by the SnII non-bonding electrons without recourse to intervalence-transfer-absorption ideas. Comparison of the complex bromides and chlorides of SnII and TeIV with the mixed-valence SbIII–SbV compounds suggests that direct population of bands rather than intervalence charge transfer may also be the dominant process in determining the properties of the antimony derivatives, l.r. data for the mixed-valence antimony compounds are consistent with the direct-population explanation.
Journal of the Chemical Society, Dalton Transactions, 1976
A Mossbauer investigation of iron-doped triglycine sulphate (tgs) has been made in order to inves... more A Mossbauer investigation of iron-doped triglycine sulphate (tgs) has been made in order to investigate the changes occurring at the iron nuclei as the properties of tgs change with temperature. Variations in the Mossbauer spectra at temperatures above the normal Curie point for undoped tgs (49 °C) have been correlated with the behaviour of polarisation-voltage hysteresis loops for the iron-doped material. The loops persist above Tc and continue to show asymmetry up to 60 °C. Above this temperature an anomalous increase in Mossbauer quadrupole splitting occurs. On cooling the specimens from 60 °C to below 49 °C the loops reappear but show no bias; bias is gradually restored over a period of hours. Similarly, the quadrupole splitting does not decrease immediately the temperature is lowered, but only after a similar period of time has elapsed. These results are discussed and possible mechanisms for the internal bias field are suggested.
Journal of The Chemical Society-dalton Transactions, 1994
The NMR and Mossbauer spectra and electrochemistry of the N-donor ferrocenyl ligands [Fe(η5-C5H5)... more The NMR and Mossbauer spectra and electrochemistry of the N-donor ferrocenyl ligands [Fe(η5-C5H5){(η5-C5H4CHNCH2Ph)}] and [Fe(η5-C5H5)(η5-C5H4CH2NMe2)] as well as their mononuclear derivatives with σ(Pd–Csp2, ferrocene) bonds [[graphic omitted]CH2Ph)}Cl(L)], [[graphic omitted]Me2)}Cl(L)][L = 1 -methylimidazole (mim) or PPh3], and [Pd{(η5-C5H5)Fe(η5-C5H3CH2NMe2)}Cl(PPh3)2] have been studied. Comparison of the data allows an understanding of the influence of the nature of the N-donor atom of the ferrocenyl moiety (sp2versus sp3) upon the properties of these compounds. In particular, the differences observed in the quadrupole splitting parameters obtained from Mossbauer spectroscopy reveal not only that the palladium(II) acts as an electron-withdrawing group in all these cyclometallated derivatives, but also that most of the electron density is withdrawn from the imine CHN moiety in the derivatives containing ferrocenyl Schiff bases as ligands. The crystal structures of [[graphic omitted]CH2Ph)}Cl(PPh3)] and [[graphic omitted]Me2)}Cl(mim)] have been determined.
Herein we describe the results of a study on the photoluminescence of cubic nanosized Y2O3:Tb. Th... more Herein we describe the results of a study on the photoluminescence of cubic nanosized Y2O3:Tb. These results confirm our earlier conclusions based on cathodoluminescence about the energy flow from excited Tb in a S6 lattice site to Tb in a C2 site.
Journal of the Chemical Society, Dalton Transactions, 1975
The ideal perovskite structure of CsSnIIBr3 at room temperature has been confirmed by a single-cr... more The ideal perovskite structure of CsSnIIBr3 at room temperature has been confirmed by a single-crystal X-ray diffraction study. It is proposed that the high-symmetry environment for the SnII in this compound arises because the distorting effect of the non-bonding electrons is reduced by their populating an empty low-energy band in the solid, thus giving rise to the black colour and metallic-conducting properties. The high-temperature phases of CsSn2IIBr5, Cs4SnIIBr6, and of compositions from the CsSnII2Br5–CsSnII2Cl5 system show similar properties. Colour can be introduced into the Cs2SnIVBr6 system by formation of mixed phases with CsSnIIBr3 which has a closely related structure. The colour and electrical properties of the mixed SnII–SnIV material can be explained by population of the low-energy delocalised solid-state bands by the SnII non-bonding electrons without recourse to intervalence-transfer-absorption ideas. Comparison of the complex bromides and chlorides of SnII and TeIV with the mixed-valence SbIII–SbV compounds suggests that direct population of bands rather than intervalence charge transfer may also be the dominant process in determining the properties of the antimony derivatives, l.r. data for the mixed-valence antimony compounds are consistent with the direct-population explanation.
Journal of the Chemical Society, Dalton Transactions, 1976
A Mossbauer investigation of iron-doped triglycine sulphate (tgs) has been made in order to inves... more A Mossbauer investigation of iron-doped triglycine sulphate (tgs) has been made in order to investigate the changes occurring at the iron nuclei as the properties of tgs change with temperature. Variations in the Mossbauer spectra at temperatures above the normal Curie point for undoped tgs (49 °C) have been correlated with the behaviour of polarisation-voltage hysteresis loops for the iron-doped material. The loops persist above Tc and continue to show asymmetry up to 60 °C. Above this temperature an anomalous increase in Mossbauer quadrupole splitting occurs. On cooling the specimens from 60 °C to below 49 °C the loops reappear but show no bias; bias is gradually restored over a period of hours. Similarly, the quadrupole splitting does not decrease immediately the temperature is lowered, but only after a similar period of time has elapsed. These results are discussed and possible mechanisms for the internal bias field are suggested.
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