Photoinduced Jahn–Teller switch in Mn(iii) terpyridine complexes

Abstract

Ultrafast transient absorption spectra were recorded for [Mn(terpy)X3], where X = Cl, F, and N3, to explore photoinduced switching from axial to equatorial Jahn-Teller (JT) distortion. Strong oscillations were observed...

Ultrafast Jahn‐Teller Photoswitching in Cobalt Single‐Ion Magnets

“…[ 27,63–66 ] The JT effect is also recognized as a mechanism that efficiently couples the molecular electronic degrees of freedom to the nuclei vibrations in the surrounding lattice. [ 67–70 ] While the JT‐SIMs reported so far have been mostly built around Mn and Cu, [ 71–74 ] the present work demonstrates that Co complexes can also be considered for developing innovative multifunctional JT‐SIMs based on their specific properties. Having a d 7 electronic configuration requiring the populations of orbitals with e g ‐like character, Co(II) complexes are invariably subject to the JT distortion, so that the process reported here is expected to be generally at play upon photoexcitation.…”

“…Moreover, whereas the JT photoswitching observed in Mnbased JT-SIMs takes place within the same spin multiplicity (e.g., quintet through 5 B 1g → 5 A 1g transition), [71,72] the flipping of the anisotropy axis in Co-based JT-SIMs involves two states of dif-ferent spin multiplicities in addition to the very short-lived intramolecular charge-transfer step at the Franck-Condon point. In contrast to most Fe(II) complexes, the spin-state transition in Co(II) complexes appears inherently coupled to large tetragonal or trigonal deformations at the molecular level.…”

Equatorial restriction of the photoinduced Jahn–Teller switch in Mn(iii)-cyclam complexes

“…Multiple frequencies suggest a complex reaction coordinate, contrasting findings for Mn 3 and Mn(terpy)X 3 (X = F, Cl, N 3 ) complexes, where restriction of the complexes only resulted in coherent oscillations from a single normal mode. 14,31…”

“…14,31 4. ConclusionPhotoexcitation of the lowest ligand-eld transition of [Mn(cyclam)(H 2 O) 2 ] 3+ (d xy ) d z 2 ) results in a switch from the axially elongated Jahn-Teller distortion present in the Q 0 ground-state (d 1 yz d 1 xz d 1 x 2 −y 2 d 1 z 2 d 0 xy ) to that in the Q 1 excited-state (d 1 yz d 1 xz d 1 x 2 −y 2 d 0 z 2 d 1 xy…”

Optical Phenomena in Molecule-Based Magnetic Materials

“…503 Moreover, the family of [Mn III (terpy)X 3 ] (terpy = 2,2′:6′,2′′-terpyridine; X = F, Cl, N 3 ) complexes showing the switching effect of JT axis was found to reveal longer dephasing times than [Mn III (acac) 3 ] complex, which was correlated with the limited number of lowfrequency vibrational modes. 504 Apart from Mn(III) complexes, lately the Co(II)-based molecular nanomagnet, [Co II (terpy) 2 ] 2+ , was studied from the point of ultrafast photoswitching in solution (Figure 17). 505 Transient absorption spectra in water were collected under 400 nm femtosecond pulses and the relative absorbance kinetics were followed at four selected wavelengths of the visible region, showing a single-exponential decay for the lowestexcited metastable state with a lifetime of 6.4(4) ps.…”