Ab Initio Calculations of the Trigonal and Zero-Field Splittings in Trischelated Diketonato Complexes of Trivalent Chromium

The ground and excited states of the neutral tris(1,3-propanedionato)chromium(III) d 3 complex are investigated with quantum chemical methods. Trigonal splittings are calculated and compared with experiment for the first two excited quartet states 4 T 2g and 4 T 1g . The effect of spin−orbit coupling is also introduced, and a reassignment is proposed for three absorption bands in the doublet region. Trigonal symmetry-induced mixing between the e g and t 2g shells is found to be responsible for the unusually large zero-field splitting of the 4 T 2g ground state. Orbitals pictures are presented which illustrate the role of the phase-coupling effect from the unsaturated ligands.