Exploring Ultrafast Photoswitching Pathways in RbMnFe Prussian Blue Analogue

Abstract

We study by femtosecond optical pump-probe spectroscopyt he photoinduced charge transfer (CT) in the RbMnFeP russian blue analogue.P revious studies evidenced the local nature of the photoinduced Mn III Fe II ! Mn II Fe III process,o ccurring within less than 1ps. Here we show experimentally that two photoswitching pathwayse xist, depending on the excitation pump wavelength, whichi sc onfirmed by band structure calculations.P hotoexcitation of a spins corresponds to the Mn(d-d) band, which drives reverse Jahn-Teller distortion through the population of antibonding Mn-N orbitals,a nd induces CT within % 190 fs.T he process launches coherent lattice torsion during the self-trapping of the CT small-polaron. Photoexcitation of b spins drives intervalence Fe !Mn CT towardsn on-bonding states and results in aslower dynamic.

Out-of-equilibrium dynamics driven by photoinduced charge transfer in CsCoFe Prussian blue analogue nanocrystals

“…All these XANES and optical data show that the early response of photoexcited CoFe particles does not depend on the size of the nanocrystals, which agrees with the local nature of the self-trapping process of the photoinduced CT polaron already highlighted in both CoFe and MnFe materials. [36][37][38] As previously discussed in detail for the CoFe PBA, the very rst step of the photoinduced dynamics corresponds to the light-induced excited spin-state trapping process (LIESST) on the Co. The initial photoexcited Co III* (S ¼ 0)Fe II (S ¼ 0) state populates antibonding Co(e g ) states, which drives Co-N bond expansion and the spin transition towards the Co III (S ¼ 2)Fe II (S ¼ 0).…”

“…Understanding and mastering the ultra-fast photoinduced intermetallic CT process is a real challenge because it requires probing the system on the sub-100 femtosecond (fs) timescale of electronic dynamics and molecular motions, as underlined in a recent review by Johansson 34 about ultrafast studies of Fe-Fe, Co-Fe, Mn-Fe, and V-Cr PBAs. 27,28,[35][36][37] We recently used femtosecond X-ray and optical absorption spectroscopies to study the CT process in a photo-excited Co III (S ¼ 0)Fe II (S ¼ 0) material (Fig. 1).…”

“…Femtosecond optical pump-probe spectroscopy experiments highlighted the local and ultrafast nature of the photoinduced Mn III Fe II / Mn II Fe III CT process. 36 Photoexcitation of a spins around 540 nm, corresponding to the Mn(d-d) band, drives reverse Jahn-Teller distortion through the population of antibonding Mn-N orbitals, and induces CT within $190 fs. The process also launches the coherent lattice torsion mode of the M-N-C-M 0 bridge during the self-trapping of the CT small-polaron.…”

“…Understanding and mastering the ultra-fast photoinduced intermetallic CT process is a real challenge because it requires probing the system on the sub-100 femtosecond (fs) timescale of electronic dynamics and molecular motions, as underlined in a recent review by Johansson 34 about ultrafast studies of Fe–Fe, Co–Fe, Mn–Fe, and V–Cr PBAs. 27,28,35–37…”

The beauty of being complex: Prussian blue analogues as selective catalysts and photocatalysts in the degradation of ciprofloxacin

“…The situation is however quite complicated, since the electronic state of Co-Fe PBAs depends on the amount of [Fe(CN) 6 ] sites, so that it is hard to predict what that is in each specific case. Furthermore, different photoswitching pathways have been very recently demonstrated and explored also in case of a RbMnFe PBA [48], evidencing the occurrence of spin transition accompanied by a lattice distortion. On the other hand, other investigations have underlined over time the general character of this intermetallic charge transfer process in compounds where the metals are cyanide-bridged [49][50][51][52][53].…”