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Proton n.m.r. spectra of furo[3,2‐ c ] and furo[2,3‐ c ]thiapyrylium cations, compared with their thieno homologues. Correlations between chemical shifts and charge densities from CNDO/2 and PPP calculations
Author(s) -
Boccuzzi Flora Catti
Publication year - 1976
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270080611
Subject(s) - cndo/2 , chemistry , spectral line , chemical shift , atomic orbital , proton , charge (physics) , molecular orbital , ring (chemistry) , charge density , sulfur , computational chemistry , electron , molecule , physics , organic chemistry , nuclear physics , quantum mechanics , astronomy
Significant variations of thiapyrylium chemical shifts, by comparison with their thienohomologues, are shown by 1 H n.m.r. spectra of furo[3,2‐c]thiapyrylium and furo[2,3‐c]thiapyrylium perchlorates. The observed changes can be ascribed to a different distribution of the electron charge (mainly caused by participation of the 3d orbitals of sulphur in the thienohomologues) and to a different contribution of the ring current; this is shown by MO calculations performed by the CNDO/2 and the coupled Hartree–Fock methods, respectively.