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Tetrakis (methylidene)cyclobutane (‘[4]Radialene’): Electronic states of the molecular ion
Author(s) -
Bally Thomas,
Buser Urs,
Haselbach Edwin
Publication year - 1978
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.19780610104
Subject(s) - chemistry , cyclobutane , degenerate energy levels , ion , symmetry (geometry) , jahn–teller effect , computational chemistry , atomic physics , crystallography , molecular physics , quantum mechanics , physics , organic chemistry , ring (chemistry) , geometry , mathematics
The photoelectron spectrum of tetrakis (methylidene)cyclobutane ( 1 , ‘[4]radialene’) is reported. The electronic states of 1 + are assigned on the basis of model calculations and with reference to related systems. Jahn ‐ Teller activity in the degenerate states is discussed. A failure of the simple LCBO‐model for the π(e g )‐orbital of 1 is noted and traced to the fact that this orbital, though having a symmetry‐equivalent π*‐counterpart, does not interact with it. This feature is confined to [4n]radialenes; their total π‐energies are therefore higher than those of the other members. It is shown that radialenes, in principle, do not constitute a class analogous to that of the linear polyenes as inferred earlier.