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Ultrafast Light-Induced Spin-State Trapping Photophysics Investigated in Fe(phen) 2 (NCS) 2 Spin- Crossover Crystal

hal.structure.identifierInstitut de Physique de Rennes [IPR]
dc.contributor.authorBERTONI, Roman
hal.structure.identifierInstitut de Physique de Rennes [IPR]
dc.contributor.authorCAMMARATA, Marco
hal.structure.identifierInstitut de Physique de Rennes [IPR]
dc.contributor.authorLORENC, Maciej
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorMATAR, Samir F.
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorLÉTARD, Jean-François
hal.structure.identifierSLAC National Accelerator Laboratory [SLAC]
dc.contributor.authorLEMKE, Henrik T.
hal.structure.identifierInstitut de Physique de Rennes [IPR]
dc.contributor.authorCOLLET, Eric
dc.date.issued2015-03-01
dc.identifier.issn0001-4842
dc.description.abstractEnFew photo-active molecules undergo a complete transformation of physical properties (magnetism, optical absorption ...) when irradiated with light. Such phenomena can happen on the time scale of fundamental atomic motions leading to an entirely new state within less than one picosecond following light absorption. Spin crossover (SCO) molecules are prototype systems having the ability to switch between low spin (LS) and high spin (HS) molecular states both at thermal equilibrium or after light irradiation. In the case of a FeII (3d6) complexes in nearly octahedral ligand field, the two possible electronic distributions among the 3d split orbitals are S = 0 for the LS diamagnetic state and S = 2 for the HS paramagnetic state. In crystals, such photo-excited states can be long-lived at low temperature, as it is the case for the photoinduced HS state of the [Fe(phen)2(NCS)2] SCO compound investigated here. We first show how such bistability between the diamagnetic and paramagnetic states can be characterized at thermal equilibrium or after light irradiation at low temperature. Complementary techniques provide invaluable insights into relationship between changes of electronic states and structural reorganization. But the development of such light-active materials requires the understanding of the basic mechanism following light excitation of molecules, responsible for trapping them into new electronic and structural states. We therefore discuss how we can observe a photomagnetic molecule during switching and catch on the fly electronic and structural molecular changes with ultra-fast x-ray and optical absorption spectroscopies. In addition, there is a long debate regarding the mechanism behind the efficiency of such a light-induced process. Recent theoretical works suggest that such speed and efficiency are possible thanks to the instantaneous coupling with the phonons of the final state. We discuss here the first experimental proof of that statement as we observe the instantaneous activation of one key phonon mode precluding any recurrence towards the initial state. Our studies show that the structural molecular reorganization trapping the photoinduced electronic state occurs in two sequential steps: the molecule elongates first (within 170 femtosecond) and bends afterwards. This dynamics is caught via the coherent vibrational energy transfer of the two main structural modes. We discuss the transformation pathway connecting the initial photo-excited state to the final state, which involves several key reaction coordinates. These results shows the need for replacing the classical single coordinate picture employed so far by a more complex multi-dimensional energy surface.
dc.description.sponsorshipEtude femtoseconde rayons X et optique de la dynamique ultrarapide de photocommutation de matériaux moléculaires magnétiques - ANR-13-BS04-0002
dc.language.isoen
dc.publisherAmerican Chemical Society
dc.title.enUltrafast Light-Induced Spin-State Trapping Photophysics Investigated in Fe(phen) 2 (NCS) 2 Spin- Crossover Crystal
dc.typeArticle de revue
dc.identifier.doi10.1021/ar500444d
dc.subject.halPhysique [physics]/Matière Condensée [cond-mat]/Science des matériaux [cond-mat.mtrl-sci]
dc.subject.halChimie/Matériaux
dc.description.sponsorshipEuropeEuropean Union (FEDER)
bordeaux.journalAccounts of Chemical Research
bordeaux.page774-781
bordeaux.volume48
bordeaux.issue3
bordeaux.peerReviewedoui
hal.identifierhal-01118869
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01118869v1
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