Ultrafast Wiggling and Jiggling: Ir2(1,8-diisocyanomenthane)4 2+

0481864 - ÚFCH JH 2018 RIV US eng J - Článek v odborném periodiku
Pižl, Martin - Hunter, B. M. - Greetham, G. M. - Towrie, M. - Záliš, Stanislav - Gray, H. B. - Vlček, Antonín
Ultrafast Wiggling and Jiggling: Ir2(1,8-diisocyanomenthane)4 2+.
Journal of Physical Chemistry A. Roč. 121, č. 48 (2017), s. 9275-9283. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA ČR GA17-01137S; GA MŠMT(CZ) LTC17052
Institucionální podpora: RVO:61388955
Klíčová slova: Coherent oscillations * Inter-system crossings * Optical spectroscopic
Obor OECD: Physical chemistry
Impakt faktor: 2.836, rok: 2017

Binuclear complexes of d(8) metals (Pt-II, Ir-I, Rh-I,) exhibit diverse photonic behavior, including dual emission from relatively long-lived singlet and triplet excited states, as well as photochemical energy, electron, and atom transfer. Time-resolved optical spectroscopic and X-ray studies have revealed the behavior of the dimetallic core, confirming that M-M bonding is strengthened upon d sigma* -> p sigma excitation. We report the bridging ligand dynamics of Ir-2(1,8-diisocyanomenthane)(4)(2+) (Ir(dimen)), investigated by fs-ns time-resolved IR spectroscopy (TRIR) in the region of C N stretching vibrations, nu(C N), 2000-2300 cm(-1). The nu(C N) IR band of the singlet and triplet d sigma*p sigma excited states is shifted by -22 and -16 cm(-1) relative to the ground state due to delocalization of the p sigma LUMO over the bridging ligands. Ultrafast relaxation dynamics of the (1)d sigma*p sigma state depend on the initially excited Franck-Condon molecular geometry, whereby the same relaxed singlet excited state is populated by two different pathways depending on the starting point at the excited-state potential energy surface. Exciting the long/eclipsed isomer triggers two-stage structural relaxation: 0.5 ps large-scale Ir-Ir contraction and 5 ps Ir-Ir contraction/intramolecular rotation. Exciting the short/twisted isomer induces a similar to 5 ps bond shortening combined with vibrational cooling. Intersystem crossing (70 ps) follows, populating a 3d sigma*p sigma state that lives for hundreds of nanoseconds. During the first 2 ps, the nu(C N) IR bandwidth oscillates with the frequency of the nu(Ir-Ir) wave packet, ca. 80 cm(-1), indicating that the dephasing time of the high-frequency (16 fs)(-1) C N stretch responds to much slower (similar to 400 fs)(-1) Ir-Ir coherent oscillations.
Trvalý link: http://hdl.handle.net/11104/0277324