Photoelectron Spectroscopy of Heterocycles. Indene Analogs
H. Güsten,a L. Klasinc,a,b and B. Ruščićc
a Institut für Radiochemie, Kernforschungszentrum Karlsruhe, Karlsruhe, Germany
b on leave from: Rugjer Bošković Institute, Zagreb, Croatia
and Faculty of Natural Sciences and Mathematics, University of Zagreb, Zagreb, Croatia
c Rugjer Bošković Institute, Zagreb, Croatia
Z. Naturforsch.
31a(9), 1051-1056 (1976)
The He(I) photoelectron (PE) spectra of indene, indole, benzofuran, benzothiophene,
1-, 2-, 3-, 4-, and 6-methylindole and 4,5,6,7-tetrafluoroindole were measured and analyzed.
A close correlation was found between the π-ionization energies of these compounds and the eigenvalues of the corresponding HMO-orbitals.
A qualitative scheme for the assignment of the π-electron ionizations by orbital interaction of the constituents of the indene analogs,
i.e. of styrene and the p-orbital of the corresponding heteroatom, indicates that the energy levels in all the compounds investigated
can be described by the same type of interaction and yields a value for the inductive effect of the hetero group
(-CH3 and >CH2: 0.3 eV; >NH: 0.4 eV; >S: 0.1 eV; >O: negligible).