Hyperchromic series

There is a close analogy between the nephelauxetic series and the series of optical electronegativities in both cases, the oxidizing character of the central ion and the reducing character of the ligands are involved. Another fact of importance for the internal transitions in the partly filled shell of complexes with centre of inversion, such as Oh, is that their intensity is inversely proportional to the square of the distance in wave-number units between the Laporte-aMovted electron transfer band and the La or/e-forbiddcn transition considered. The complexes have been arranged in a hyperchromic series with respect to this variation of intensities. 

Yamada and Tsuchida (1953) introduced a hyperchromic series of intensities of cobalt(III) complexes, which is also valid for other octahedral, typical Werner complexes of chromium(III) and rhodium(III) ... 

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