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Ring-constrained derivatives studies

The first summation constrains the conformational torsion angles (and sometimes the covalent bond angles) to lie near to the expected values derived from single crystal and polymer studies the second summation minimizes the differences between the observed and calculated X-ray structure factor amplitudes the third summation relaxes unfavourable non-bonded interactions and the fourth summation contains constraints Hn whose values are zero when residue connectivity and furanose ring closure have been achieved. [Pg.37]

Although there has been much theoretical study of the spectra of porphin and its metal derivatives (137, 138, 230, 283), comparatively little has been said about the metal phthalocyanines. It has been generally assumed that the theory developed for porphin will apply equally to the phthalocyanines. Two general approaches have been used to interpret the spectra of the phthalocyanines. In the Free Electron Gas model, developed by Kuhn (201-206, 309) in a manner similar to that of Simpson (327), the phthalocyanine unit is regarded as a polyene in which the ir electrons are constrained to move in a closed ring-shaped path, in a field of constant... [Pg.71]


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Constrained derivatives

Ring-constrained derivatives

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