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Halogen Substitution Effects on N 2 O Schiff Base Ligands in Unprecedented Abrupt Fe II Spin Crossover Complexes
Author(s) -
Phonsri Wasinee,
Macedo David S.,
Vignesh Kuduva R.,
Rajaraman Gopalan,
Davies Casey G.,
Jameson Guy N. L.,
Moubaraki Boujemaa,
Ward Jas S.,
Kruger Paul E.,
Chastanet Guillaume,
Murray Keith S.
Publication year - 2017
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.201700232
Subject(s) - spin crossover , halogen , crystallography , schiff base , spin transition , chemistry , spin states , spin (aerodynamics) , inorganic chemistry , physics , thermodynamics , organic chemistry , alkyl
A family of halogen‐substituted Schiff base iron(II) complexes, [Fe II (qsal‐X) 2 ], (qsal‐X=5‐X‐ N ‐(8‐quinolyl)salicylaldimines)) in which X=F ( 1 ), Cl ( 2 ), Br ( 3 ) or I ( 4 ) has been investigated in detail. Compound 1 shows a temperature invariant high spin state, whereas the others all show abrupt spin transitions, at or above room temperature, namely, 295 K (X=I) up to 342 K (X=Br), these being some of the highest T 1/2 values obtained, to date, for Fe II N/O species. We have recently reported subtle symmetry breaking in [Fe II (qsal‐Cl) 2 ] 2 with two spin transition steps occurring at 308 and 316 K. A photomagnetic study reveals almost full HS conversion of [Fe II (qsal‐I) 2 ] 4 at low temperature ( T (LIESST)=54 °K). The halogen substitution effects on the magnetic properties, as well as the crystal packing of the [Fe II (qsal‐X) 2 ] compounds and theoretical calculations, are discussed in depth, giving important knowledge for the design of new spin crossover materials. In comparison to the well known iron(III) analogues, [Fe III (qsal‐X) 2 ] + , the two extra π–π and P4AE interactions found in [Fe II (qsal‐X) 2 ] compounds, are believed to be accountable for the spin transitions occurring at ambient temperatures.