Computation of ultraviolet and visible spectra for cobalt acetylacetonate

A computation is made for the Co(acac)₃ molecule by the semiempirical method of Mulliken, Helmholz, and Wolfsberg. The results indicate a high degree of covalence in the metal—ligand bond. Analysis of the obtained system of energy levels and oscillator forces for the possible transitions makes it possible to interpret the 1100 nm and 800 nm bands as transitions from the -orbitals of the carbon atoms in the ortho position to the metal to the d orbitals of the metal; the bands in the 400- to 610-nm region are interpreted as d()-d transitions, which cannot be regarded as pure d-d transitions. The bands in the region below 400 nm are attributed to - transitions. The calculation also shows that in complexes with covalent metal-ligand bonds the levels, to which the main contribution is made by the atomic orbitals of the metal and the directly coordinated atoms, are mixed.