Electron solid state studies

This chapter will concentrate on the electronic spin-state crossover observed in the iron and cobalt complexes formed with the HB(pz)3 and HC(pz)3 ligands and their various methyl derivatives. In the majority of cases, the spin-state crossover occurs in the solid state and, as a consequence, solid state studies will be covered first, followed by the more limited studies... 

The problems associated with the study of solids and the means to overcome them having been outlined, it is of value to the prospective user of n.m.r.in catalysis to be aware of the compromises which should be considered before embarking on the purchase of equipment. Although the general trend is towards buying n.m.r. spectrometers already equipped for solid-state studies, it is feasible to modify conventional liquid-state spectrometers.35 Some additional hardware is required and a good knowledge of electronics. Details of the spectrometer itself have been described.1,36 -40 A few comments are merited on each of the essential features required to be able to perform the majority of the studies described in this review. 

NIR fluorescence for bioanalytical applications is of importance in diagnosing disease and NIR-absorbing phthalocyanines may be used as fluorescence probes [5], Thus, this chapter concentrates on phthalocyanine complexes absorbing from about 730 nm upwards. Even though solid state electronic absorption spectra of Pc thin films are known to be red-shifted [6-9], this work focuses on solution studies with only a few examples of the solid state studies. 

Gas-phase study G. Schultz, I. Hargittai, Electron diffraction investigation of ethane-1,2-dithiol. Acta Chim. Hung. 1973, 75, 381-388 solid-state study M. Hayashi, Y. Shiro, T. Oshima, and H. Murata, The Vibrational Assignment, Rotational Isomerism and Force Constants of 1,2-Ethanedithiol. Bull. Chem. Soc. Japan 1965, 38, 1734-1740. 

Detailed description of the wealth of techniques available for studying such systems is beyond the scope of this book. However, the authors have attempted to provide a broad overview of some of the approaches which can be undertaken for identification of radical damage which DNA may have experienced in intact cellular systems or for standard assessment of the ways in which DNA may be damaged by these reactive species. As well as the use of cell systems we also use liquid-phase studies on dilute solutions of DNA to illustrate the effects of OH radical damage, and solid-state studies to show the effects of electron-gain and -loss. 

The debate over the site of electron loss in DNA is much less pronounced since it has been estimated that over 90% of the cations generated in DNA are centered on guanine [67] and guanine end products account for 90% of the electron loss products in DNA [70]. However, the spectra of G recorded in solid-state studies of nucleotides and nucleosides do not correspond to the spectrum recorded in fiiU DNA [71] and investigations of the strand-break specificity determined that some adenine cations could be generated [64]. Thus, it is also possible that other cations are formed, primarily A. ... 

Also rather few solid state metal NMR spectra of clusters have been reported. This type of experiment is very promising for the metal NMR of clusters, basically for two reasons. First, solid state NMR gives tensorial values of the chemical shifts, and the anistropy of coupling constants reflecting more precisely the electronic structure. The measurement of dipole-dipole interactions, where possible, should allow the determination of distances involving light nuclei such as H, Li, Be which are not easily accessible by X-ray diffraction. The second reason for interest in solid state studies is that the fluxional behaviour is often frozen out and that consequently NMR results are more amenable to correlation with X-ray studies. 

All the structural information for carbonyl difluoride relates to the gas phase there are no solid state studies. Carbonyl difluoride exhibits C y symmetry its characteristic structural parameters have been established from electron diffraction and microwave spectroscopic data, and are summarized in Table 13.17. Of these data, those of Nakata et al. [1480] are the most precise. 

Actinide elements (Z = 89 - 103) include the heaviest natural and most of the synthetic transuranium elements. They form a series of transition elements, characterized by the filling of an inner - the 5f-electron shell. The elements from Ac (Z = 89) to Es (Z = 99) are available in quantities sufficient for solid state studies. Elemental actinides are metallic. The methods of metal preparation and characterization have been improved to yield samples of known purity and crystal structure, sometimes in the form of single crystals. Recent measurements of structural, thermodynamic and electronic properties have emphasized elements in the beginning and in the centre of the actinide series. 

FIGURE 21-5 Carbon Is X-ray photoelectron spectrum lor ethyl trifluoroacetale. (From K. Siegbahn et ai.. ESCA Atomic, Molecular, and Solid State Studies by Means of Electron Spectroscopy, p. 21. Upsala Almqulsi and Wiksells. 1967. With permission.)... 

The lowest electronic transition of gaseous HSO A A -X A") is well known in both absorption (540-590 nm) [33] and emission [29]. The 0-0 transition in the emission spectrum has been identified at 696 nm [29] which gives the excited state energy as 1.78 eV. This absorption has never been observed in solid state studies of RSO radicals. Perhaps it is too weak to be detected at the RSO concentrations attained in those studies. 

Siegbahn, K., Nordling, C., Fahlman, A., Nordberg, R., Hamerin, K., Hedman, J., Johansson, G., Bergmark, T., Karlsson, S.-E., Lindgren, I. and Lindberg, B. (1967) Electron Spectroscopy for Chemical Analysis Atomic, Molecular, and Solid State Structure Studies by Means of Electron Spectroscopy, Almqvist and Wiksells, Uppsala. 

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