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  4. Structure:function relationships for thermal and light-induced spin-crossover in isomorphous molecular materials
 
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research article

Structure:function relationships for thermal and light-induced spin-crossover in isomorphous molecular materials

Kulmaczewski, Rafal
•
Trzop, Elzbieta
•
Collet, Eric
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July 7, 2020
Journal Of Materials Chemistry C

Isomorphous [FeL2]BF4center dot solv and [FeL2]ClO4center dot solv (L = 4-{isopropylsulfanyl}-2,6-di{pyrazol-1-yl}pyridine; solv = MeNO2, MeCN, 0.67Me(2)CO or H2O) exhibit a variety of thermal spin-crossover (SCO) behaviours. This complexity extends to the light induced excited spin state trapping (LIESST) experiment where, uniquely, five members show the expected inverse relationship between their thermal SCO (T-1/2) and LIESST relaxation (T(LIESST)) temperatures but a sixth compound ([FeL2]BF4center dot MeCN) does not. The structural basis of these observations has been probed by X-ray crystallography, photocrystallography and periodic DFT+U+D2 calculations. Among the compounds examined, more cooperative thermal SCO is strongly coupled to order/disorder transitions in the solvent and/or isopropyl substituents andvice versa. A series of symmetry breaking phase transitions in [FeL2]BF4center dot MeNO2, before and after photoexcitation, occurs 10-20 K belowT(LIESST) and has no direct bearing on theT(1/2)/T(LIESST) relationship. These phase changes are not shown by other compounds in the study. The anomalousT(LIESST) in [FeL2]BF4center dot MeCN, and its observed negative lattice expansion during isothermal low -> high-spin conversion, are not reproduced computationally which implies those properties are unconnected to its spin state energetics. Its minimised high- and low-spin structures also deviate more from experiment than the other compounds investigated, in the most plastic region of the lattice which includes the solvent molecule. We conclude that reorientation of the linear MeCN molecule contributes a temperature-dependent lattice activation barrier to the spin-transition in [FeL2]BF4center dot MeCN, leading to the higherT(LIESST) value observed.

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Type
research article
DOI
10.1039/d0tc02174a
Web of Science ID

WOS:000545331300005

Author(s)
Kulmaczewski, Rafal
•
Trzop, Elzbieta
•
Collet, Eric
•
Vela, Sergi  
•
Halcrow, Malcolm A.
Date Issued

2020-07-07

Publisher

ROYAL SOC CHEMISTRY

Published in
Journal Of Materials Chemistry C
Volume

8

Issue

25

Start page

8420

End page

8429

Subjects

Materials Science, Multidisciplinary

•

Physics, Applied

•

Materials Science

•

Physics

•

intermolecular interactions

•

coordination polymer

•

phase-transitions

•

iron(ii) complex

•

photomagnetism

•

fluorescence

•

conversion

•

hysteresis

•

dependence

•

behaviors

Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
ISIC  
Available on Infoscience
July 18, 2020
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/170228
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