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Spin Crossover in a Hexaamineiron(II) Complex: Experimental Confirmation of a Computational Prediction
Author(s) -
Bernhardt Paul V.,
Bilyj Jessica K.,
Brosius Victor,
Chernyshov Dmitry,
Deeth Robert J.,
Foscato Marco,
Jensen Vidar R.,
Mertes Nicole,
Riley Mark J.,
Törnroos Karl W.
Publication year - 2018
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.201705439
Subject(s) - spin crossover , cooperativity , chemistry , spin states , ground state , ising model , spin transition , enthalpy , spin (aerodynamics) , condensed matter physics , thermodynamics , crystallography , physics , atomic physics , inorganic chemistry , biochemistry
Single crystal structural analysis of [Fe II (tame) 2 ]Cl 2 ⋅MeOH (tame=1,1,1‐tris(aminomethyl)ethane) as a function of temperature reveals a smooth crossover between a high temperature high‐spin octahedral d 6 state and a low temperature low‐spin ground state without change of the symmetry of the crystal structure. The temperature at which the high and low spin states are present in equal proportions is T 1/2 =140 K. Single crystal, variable‐temperature optical spectroscopy of [Fe II (tame) 2 ]Cl 2 ⋅MeOH is consistent with this change in electronic ground state. These experimental results confirm the spin activity predicted for [Fe II (tame) 2 ] 2+ during its de novo artificial evolution design as a spin‐crossover complex [ Chem. Inf. Model . 2015 , 55 , 1844], offering the first experimental validation of a functional transition‐metal complex predicted by such in silico molecular design methods. Additional quantum chemical calculations offer, together with the crystal structure analysis, insight into the role of spin‐passive structural components. A thermodynamic analysis based on an Ising‐like mean field model (Slichter–Drickammer approximation) provides estimates of the enthalpy, entropy and cooperativity of the crossover between the high and low spin states.