IX. Calculations of electronic spectra of transition metal complexes

Abstract

This chapter provides a detailed overview of possible computational methods for the calculation of excited states in transition metal complexes. A few selected examples are presented that illustrates the distinct power of accurate computations for the interpretation of experimental spectroscopic features. The chapter also presents discussion of the specific electronic structure and metal-ligand bonding interactions giving rise to these features. The examples are taken from various fields of chemistry and include different types of excitations. The chapter focuses on the ligand field spectra of Co(II) and Cu(II) as probes of the coordination environment of these ions when bound to a zeolite surface and contains a discussion of the long-standing and heavily debated spectrum of the permaganate ion, that is a pure charge transfer spectrum. The chapter discusses the electronic structure of two important classes of redox proteins, namely the blue copper proteins and a series of mononuclear oxomolybdenum enzymes, modeled by the (Tp)MoO(bdt) compound (with Tp = hydrotris(1-pyrazolyl)borate and bdt = benzenedithiolate). In both cases, the considered electronic spectra are built from a mixtures of LF states and a number of low-lying LMCT states. All excited state calculations reported in the chapter are performed by means of the CASPT2//CASSCF method as implemented in the Molcas software.