The properties of transition metal compounds have fascinated physicists and chemists for a long time. These compounds have an enormous potential for future applications of solar energy conversion, information storage systems, chemical or biochemical sensors, lowdimensional semiconductors, supramolecular systems, chemical synthesis, etc. Most of these applications are related to the characteristics of the low-lying electronic and vibronic states. In the present volume as well as in its companion volume 1 leading researchers - physicists and chemists - present theoretical as well as experimental approaches towards a deeper understanding of these compounds. Both volumes build a bridge between physicists and chemists by showing how controlled chemical variations can be applied to tune physical properties in a defined way and vice versa, by demonstrating how detailed spectroscopical and quantum mechanical investigations allow the chemical characterization of ground and excited states.