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Spin Crossover and Long‐Lived Excited States in a Reduced Molecular Ruby
Author(s) -
Becker Patrick M.,
Förster Christoph,
Carrella Luca M.,
Boden Pit,
Hunger David,
Slageren Joris,
Gerhards Markus,
Rentschler Eva,
Heinze Katja
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.202001237
Subject(s) - chromium , spin crossover , excited state , microsecond , electron paramagnetic resonance , chemistry , pyridine , crystallography , diamine , photochemistry , materials science , nuclear magnetic resonance , atomic physics , physics , optics , medicinal chemistry , organic chemistry
The chromium(III) complex [Cr III (ddpd) 2 ] 3+ (molecular ruby; ddpd= N , N′ ‐dimethyl‐ N , N′ ‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) is reduced to the genuine chromium(II) complex [Cr II (ddpd) 2 ] 2+ with d 4 electron configuration. This reduced molecular ruby represents one of the very few chromium(II) complexes showing spin crossover (SCO). The reversible SCO is gradual with T 1/2 around room temperature. The low‐spin and high‐spin chromium(II) isomers exhibit distinct spectroscopic and structural properties (UV/Vis/NIR, IR, EPR spectroscopies, single‐crystal XRD). Excitation of [Cr II (ddpd) 2 ] 2+ with UV light at 20 and 290 K generates electronically excited states with microsecond lifetimes. This initial study on the unique reduced molecular ruby paves the way for thermally and photochemically switchable magnetic systems based on chromium complexes complementing the well‐established iron(II) SCO systems.