Harry B. Gray), zalis@jh-inst.cas.cz (Stanislav Záliš), a.vlcek@qmul.ac.uk (Antonín Vlček) Dedicated to Barry Lever, consummate scholar and treasured friend, in recognition of his deep and lasting contributions to coordination chemistry. Abstract Research on d 8 -d 8 complexes is being actively pursued, owing, in part, to newly developed timeresolved optical, IR, and X-ray methods that directly interrogate bonding changes upon excitation. Our review covers work on the ground-and electronic excited states, as well as the oxidized and reduced forms, of these complexes. Recent experimental and theoretical results add a new chapter to the rich history of d 8 -d 8 spectroscopic and chemical behavior.2 4.2. 3 dσ*pσ decay mechanism ……………………………………………………………………………………….. 4.3. Singlet and triplet excited-state properties and reactivity ………………………………………… 4.4. Excited-state spectroscopy ………………………………………………………………………………………. 4.5. Vibrational coherence ……………………………………………………………………………………………… 4.6. Relaxation of higher excited states …………………………………………………………………………… 4.7. Metal-metal to ligand charge transfer and ligand-centered excited states ………………. 5. Conclusions …………………………………………………………………………………………………………………………….. Acknowledgments ……………………………………………………………………………………………………………………… Appendix: computational details ………………………………………………………………………………………………… References ………………………………………………………………………………………………………………………………….