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Synthesis and Characterisation of Two New Iron(II) Spin‐Crossover Complexes with N 4 O 2 Coordination Spheres – Optimizing Preconditions for Cooperative Interactions
Author(s) -
Weber Birgit,
Kaps Eike S.,
Desplanches Cedric,
Létard JeanFrançois,
Achterhold Klaus,
Parak Fritz G.
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800420
Subject(s) - chemistry , spin crossover , spin transition , spin states , photoexcitation , crystallography , excited state , magnetic susceptibility , coordination complex , mössbauer spectroscopy , thermal hysteresis , jahn–teller effect , ion , condensed matter physics , atomic physics , inorganic chemistry , phase transition , metal , physics , organic chemistry
Two new spin‐crossover complexes, [FeL1(phpy) 2 ] ( 1 ) and [FeL2(phpy) 2 ](phpy) ( 2 ), with L1 and L2 being tetradentate N 2 O 2 2– ‐coordinating Schiff‐base‐like ligands {L1 = ( E , E )‐[diethyl 2,2′‐[1,2‐phenylenebis(iminomethylidyne)]bis(3‐oxobutanoato)(2–)‐ N , N ′,O 3 ,O 3 ′], L2 = [(3,3′)‐[1,2‐phenylenebis(iminomethylidyne)]bis(2,4‐pentanedionato)(2–)‐ N , N ′,O 2 ,O 2 ′]and phpy = 4‐phenylpyridine} have been investigated using temperature‐dependent susceptibility and photomagnetic measurements, as well as Mössbauer spectroscopy and X‐ray structure analysis. Compound 1 shows a cooperative spin transition with a thermal hysteresis loop approximately 4 K wide ( T 1/2↓ = 232 K and T 1/2↑ = 236 K). The spin transition of 2 is gradual with T 1/2 ≈ 290 K. Results from X‐ray structure analysis indicate that the cooperative interactions are due to elastic interactions with several intense C–C contacts in the case of 1 . The change of the spin state at the iron centre is accompanied by a change of the O–Fe–O angle, the so‐called bite of the equatorial ligand, from 107° in the high‐spin state to 89° in the low‐spin state. Reflectivity measurements of 1 indicate that the Light‐Induced Excited Spin State Trapping (LIESST) effect occurs at the sample surface at low temperatures. In the bulk solid, photomagnetic properties with a photoexcitation level of 30 % and a T (LIESST) value of 41 K are observed using a SQUID magnetometer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)