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Computation of the ESR. Coupling Constants of the [16]Annulene Radical Anion; Theoretical and Experimental Reinvestigation of the Excited States of [16]Annulene and its Mono‐ and Dinegative Ions
Author(s) -
Baumann Harold,
Oth Jean F. M.
Publication year - 1980
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19800630309
Subject(s) - annulene , chemistry , ion , coupling constant , excited state , spectral line , coupling (piping) , computational chemistry , atomic physics , photochemistry , crystallography , quantum mechanics , physics , organic chemistry , mechanical engineering , engineering
The problem of assigning the two small ESR. coupling constants of the [16]annulene radical anion to the two sets of four equivalent outer and inner ring protons is treated by three different semiempirical MO methods. All three methods indicate that the smaller coupling constant (0.743 Gauss) should be assigned to the inner protons, and the larger one (0.963 Gauss) to the outer ones. The electronic spectra of [16]annulene, its radical anion, and its dianion have been remeasured. Especially interesting was the detection of a symmetry‐forbidden band of the radical anion at 1473 nm (6789 cm −1 , logε 2.57). The spectra are discussed in terms of different MO models.