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Tracking the Light‐Induced Excited‐State Dynamics and Structural Configurations of an Extraordinarily Long‐Lived Metastable State at Room Temperature
Author(s) -
Iglesias Sirma,
Gamonal Arturo,
Abudulimu Abasi,
Picón Antonio,
Carrasco Esther,
Écija David,
Liu Cunming,
Luer Larry,
Zhang Xiaoyi,
Costa José Sánchez,
Moonshiram Dooshaye
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001393
Subject(s) - metastability , spin crossover , excited state , microsecond , chemistry , x ray absorption spectroscopy , relaxation (psychology) , ultrafast laser spectroscopy , spectroscopy , chemical physics , ground state , spin states , density functional theory , spin (aerodynamics) , absorption spectroscopy , atomic physics , crystallography , computational chemistry , physics , thermodynamics , optics , social psychology , psychology , inorganic chemistry , organic chemistry , quantum mechanics
Time‐resolved X‐ray (Tr‐XAS) and optical transient absorption (OTA) spectroscopy on the pico‐microsecond timescale coupled with density functional theory calculations are applied to study the light‐induced spin crossover processes of a Fe‐based macrocyclic complex in solution. Tr‐XAS analysis after light illumination shows the formation of a seven‐coordinated high‐spin quintet metastable state, which relaxes to a six‐coordinated high‐spin configuration before decaying to the ground state. Kinetic analysis of the macrocyclic complex reveals an unprecedented long‐lived decay lifetime of approximately 42.6 μs. Comparative studies with a non‐macrocyclic counterpart illustrate a significantly shortened approximately 568‐fold decay lifetime of about 75 ns, and highlight the importance of the ligand arrangement in stabilizing the reactivity of the excited state. Lastly, OTA analysis shows the seven‐coordinated high‐spin state to be formed within approximately 6.2 ps. These findings provide a complete understanding of the spin crossover reaction and relaxation pathways of the macrocyclic complex, and reveal the importance of a flexible coordination environment for their rational design.