ABSTRACT

Ruthenium polyimine complexes have been one of the central subjects of inorganic electrochemistry and photochemistry. This chapter aims to tune the orbitals of ruthenium polyimine complexes making use of interactions between the ruthenium and the ligands orbitals. Starting from the basic principles, selected examples of design of non-pyridine-based ligands and "active tuning" are discussed for the tuning of orbital energies of the ruthenium complexes, followed by the discussion of applications to dye-sensitized solar cells and organic light-emitting diodes from the orbital viewpoints. Specific examples of orbital tuning of ruthenium complexes are given on cyclometalated complexes and complexes with azole/azolate ligands, among others. Theoretical interpretation of properties of metal complexes is done by density functional theory computation most of the cases at the research level. The chapter describes cyclometalated ruthenium complexes followed by azole ligands. It discusses some examples of ruthenium complexes with nonstandard geometries. The azole group is deprotonated in the complexes, coordinating to ruthenium as an azolate anion.