Solid State Structural Studies

The determination of crystal structures for many platinum metal—nucleobase complexes has elucidated many of the binding features, although the foregoing discussion is evidence of the complexity of these mixtures in solution. The bases studied range from unsubstituted purines and pyrimidines to the nucleosides and nucleotides. One feature of this area is the general difficulty of obtaining suitable crystalline samples of the sugar 

Selected structural parameters for complexes of general type cis-[Pt(am)2 (nucleobase)2] 

The conventions for this analysis have been laid down in some detail by Marzilli and co-workers [71, 72]. The major conformational parameters for c/s(bisnucleobase) complexes, where in fact the bases may be the same or two different bases, are defined as  

In structural work, the exact conformation may be affected by a combination of intra- and inter-complex interactions such as counterion, medium of recrystallization, hydrogen bonding and steric effects of the particular substituted nucleobase studied [4, 5]. These effects have to be somewhat separated from inherent effects such as the dihedral angles discussed above, although the interplay is complicated. The various parameters have been summarized for bis(purine), bis(pyrimidine) and mixed purine and pyrimidine complexes and for hydrogen bonding patterns. The reader is referred to the references [69—71] for detailed analysis of these points. 

Firstly, it should be noted that with the exception of the first complex in 

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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. 

G. Johansson,T. Bergmark, S.-E. Karls-SON, E Lindgreen, B. Lindberg ESCA Atomic, Molecular, and Solid State Structure Studied by Means of Electron Spectroscopy. Almqvist and Wiksells, Uppsala 1967. 

Siegbahn K, Nordling C, Fahlman A, Nordberg R, Hamrin K, Hedman J, Johansson G, Bergmark T, Karlsson S-E, Lindgren I, Lindberg B (1967) ESCA atomic, molecular and solid state structure studied by means of electron spectroscopy. Almqvist and Wiksells Bok-tryckeri, Uppsala... 

Siegbahn, K., etal ESCA atomic molecular and solid-state structure studied by means of electron spectroscopy. Uppsala Almqvist and Wiksells AB 1967... 

Siegbahn, K. et al., ESCA, Atomic, Molecular, and Solid State Structure Studied... 

Thus, solution and solid-state structural studies of such fluoroolefin compounds have helped to formulate and refine theories of metal-carbon bonding. Studies of the reactivity of metal-fluoroolefin compounds have also provided useful models and predictions for hydrocarbon systems. For example, the oxidative cyclization of fluoroolefins within the coordination sphere of a metal to give metallacyclopentane compounds was discovered many years before the importance of the corresponding reaction of hydrocarbon olefins was realized (3). 

Electron Spectroscopy for Chemical Analysis Atomic, Molecular and Solid State Structure Studies hy means of Electron Spectroscopy. Almquist and Wiksells, Stockholm, 1967. 

Of the various techniques routinely available, IR and 13C NMR spectroscopy usually provide the most valuable information in terms of the determination of the most appropriate valence description (A-D, Chart 1) of the carbon fragment. Mossbauer spectroscopy has also been used with good effect with iron-containing poly-carbon complexes.89 This solution-based work is complemented by a significant number of solid-state structural studies, which are described in greater detail below. Electronic spectroscopic methods, including luminescence methods, have been used to probe the electronic structures of a small number of poly-yndiyl complexes and polymers.288 315 340 342 377 380 Selected IR, 13C NMR, and UV-vis data have been given in Tables I-VIII, above. 

K.Siegbahn, C.Nording, A. Fahlman, R.Nordberg, K.Hamrin, J.Hedman, G.Johansson, T.Bergmark, S.-E.Karlsson, I.Lindgren and B.Lindberg, ESCA Atomic, Molecular and Solid State Structure Studies by Means of Electron... 

The synthesis of rubyrin 7.25 involves an acid-catalyzed 4 + 2 MacDonald-type condensation between the diformyl bipyrrole 7.21 and the diacid tetrapyrrane 7.23 (Scheme 7.2.1). After oxidation and purification, a roughly 20% yield of a blue crystalline solid is obtained, which, on the basis of solution-phase spectroscopic and solid-state structural studies vide infra), was assigned the hexapyrrolic structure 7.25. Using a similar procedure, rubyrins 7.26 and 7.27 were also prepared. While the first of these (like 7.25) proved stable, rubyrin 7.27 was found to decompose during chromatographic purification. It was thus characterized only by UV-vis spectroscopy and mass spectrometry. ... 

The dimeric structure for (II) was confirmed by solid-state structural studies [MRa = GeClg 354), Gelg 347), GeMea 354), SiMca 347)]. 

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