Electronic structures and photophysics of d8-d8 complexes

Abstract

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 ………………………………………………………………………………………………………………………………….

Ultrafast Wiggling and Jiggling: Ir2(1,8-diisocyanomenthane)42+

“…Looking ahead, TRIR has the potential to monitor interactions between electronically excited Ir(dimen) and substrates, including accompanying changes in electron density distributions and Ir oxidation states. Our finding of bridging-ligand vibrational response to Ir-Ir wave packet oscillations demonstrates that coherent effects in d 8_ d 8 complexes 1,3,6,9 extend well beyond the central dimetallic unit, thereby indicating that excited-state reactions (e.g., electron-, energy-, or atom transfer) could be coupled to intramolecular coherent motions triggered by ultrafast excitation.…”

“…In d 8_ d 8 complexes, ISC requires either a structural distortion to promote spin-orbit coupling (SOC) between the dσ*pσ singlet and triplet or a low-lying intermediate state allowing second-order SOC and/or a thermally activated pathway. 1,3,25,26,27,28 The ~70 ps ISC in Ir(dimen) is faster than in the structurally more rigid isocyanide-bridged complexes of Rh(I) and Ir(I) (230 ps -1.3 ns). 1,29,30 The dimen ligand flexibility likely enables ISC-promoting structural distortions through thermal fluctuations.…”

“…TDDFT optimization of excited-state structures (in MeCN -continuum dielectric model, Table S6) yielded a single stable minimum for 1 Figure S18.) The spin density in the optimized 3 dσ*pσ state ( Figure S19) is largely localized in π*(C≡N) orbitals oriented parallel with the Ir-Ir axis.…”

“…3,5,6 Many of these complexes also are redox-active, most especially as powerful reductants and oxidants in photoinduced electron-and atom transfer reactions. 1 II , and Au III complexes also exhibit rich photoluminescence and photochemistry. 7 Investigations of d 8_ d 8 excited-state structures and dynamics have focused on the dimetallic unit.…”

“…1,2,3,4 Of particular interest is that the slow rates of excited singlet to triplet intersystem crossing (ISC) have allowed workers to detect and characterize the two spin states separately. 3,5,6 Many of these complexes also are redox-active, most especially as powerful reductants and oxidants in photoinduced electron-and atom transfer reactions.…”