JO URNAL O F ELEC TRO N SPEC TRO !iC O PY and Related Phenomena zyxwvutsrqponm ELSEVIER Journal of Electron Spectroscopy and Related Phenomena 70 (1994) 83-88 Effect of y substitution on the X-ray emission spectra and electronic structure of iron(II1) and cobalt(II1) acetylacetonates O.L. Shchekaa>*, T.B. Emelinaa, V.D. Yumatovb zyxwvutsrqponmlkjihgfedcbaZYX aLuboratory of Electron Spectroscopy, Physical and Technical Institute, Far Eastern State University, 25 Uborevitcha Str., Vladivostok 690600, Russian Federation ‘Institute of Inorganic Chemistry, Siberian Division of Russian Academy of Sciences, Novosibirsk 630090, Russian Federation First received 23 September 1993; in final form 2 April 1994 Abstract The electron structure of Fe(acac), and Co(acach and their -y-halogen substituted compounds has been investigated by using X-ray emission spectroscopy of the vapours. The experimental data are compared with the results of theoretical calculations (XWDV method). The effects of y substitution in ligands on the X-ray emission fine structure and stabilization of occupied orbitals are discussed. Keywords: Acetylacetonate; Cobalt compound; Iron compound; UVPES; XES; XWDV 1. Introduction The effect of y substitution in transition metal ,0- diketonates on the electronic structure of chelate cycles was investigated earlier by ultraviolet photo- electron (UVPE) spectroscopy [1,2]. This method allows one to obtain the exact ionization energies of the highest occupied molecular orbitals (HOMOs), but their structure cannot be determined directly by the UVPE method. An application of X-ray emission (XE) spectroscopy for studying the elec- tronic structure of acetylacetonates of aluminium [3] and copper [4-71 provided detailed data about the atomic composition of the valence occupied orbitals. These studies were carried out for solids so the authors [3-71 could not analyse the more informative 0 Ka spectra owing to the possible * Corresponding author. presence of adsorbed oxygen on the surface of the sample. The XE spectroscopic study of the vapours of copper(I1) and iron(II1) acetylacetonates and their P-substituted derivatives was free from such problems [8] and so allowed determination of the M-L chemical bonding character. The use of the X-ray emission spectra of iron(II1) and cobalt(II1) ,Bdiketonate vapours and their y-halogen sub- stituents provided the possibility of answering some questions that were raised under the UVPE study [9,10]. Unfortunately CND0/2 calculations used for the interpretation of the experimental data did not allow a correct explanation of the peculia- rities of the y-substitution effect on the electronic structure of chelate cycles and on the metal-ligand chemical bonding character. This semiempirical method does not take into account a Koopman’s theorem violation for the transition metal chemical compounds. Here we have used the Xa discrete 0368-2048/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDI 0368- 2048(94)02213- J