The photoelectron spectra of some 1,9-disubstituted phenalenes

Abstract

The He^I vapour phase photoelectron spectra of six 1,9-disubstituted phenalenes have been measured. Data are given for 9-methylaminophenalen-1-one, 9-dimethylaminophenalen-1-one, 9-mercaptophenalen-1-one, 9-methylamino-1-methyliminophenalene, 9-methylaminophenalene-1-thione, and 9-isopropylaminophenalen-1-thione. Observed band shifts in the low ionization energy region (< 11 eV) are discussed in terms of substituent lone-pair interactions with the phenalene σ–π molecular network in a manner consistent with the results of SPINDO calculations and a simple correlation procedure. For all compounds the semi-empirical calculations indicate that four of the six uppermost orbitals are ring π orbitals and that two are substituent lone-pair orbitals, one of which is considerably delocalized in nature.