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Synthesis, Structure and Properties of a Mixed Mononuclear/Dinuclear Iron(II) Spin‐Crossover Compound with the Ligand 4‐( p ‐Tolyl)‐1,2,4‐triazole
Author(s) -
A. Kolnaar Jeroen J.,
de Heer Martine I.,
Kooijman Huub,
Spek Anthony L.,
Schmitt Georg,
Ksenofontov Vadim,
Gütlich Philipp,
Haasnoot Jaap G.,
Reedijk Jan
Publication year - 1999
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/(sici)1099-0682(199905)1999:5<881::aid-ejic881>3.0.co;2-q
Subject(s) - chemistry , crystallography , denticity , triclinic crystal system , molecule , triazole , ligand (biochemistry) , hydrogen bond , 1,2,4 triazole , spin crossover , crystal structure , stereochemistry , spin transition , medicinal chemistry , organic chemistry , biochemistry , receptor
A new iron(II) compound with the formula [Fe 2 (L) 5 (NCS) 4 ] 2 [Fe(L) 2 (NCS) 2 (H 2 O) 2 ] ( I ) [where L = 4‐( p ‐tolyl)‐1,2,4‐triazole] has been synthesized and subjected to X‐ray structure determination. Compound I crystallizes in the triclinic space group P –1 (no. 2) with a = 14.5785(11), b = 16.1253(11), c = 16.1963(8) Å, α = 80.930(5), β = 85.796(5), γ = 78.132(6)°, V = 3676.2(4) Å 3 . The structure refinement converged to wR 2 = 0.172, R F = 0.084. The structure was found to consist of two types of iron‐containing structural units, a mononuclear unit and a dinuclear one. The mononuclear unit has a crystallographic inversion centre, and is coordinated by two N CS anions, two triazole N1 nitrogen atoms, and two water molecules, each hydrogen‐bonded to one of the two dinuclear units. The dinuclear units consist of two iron(II) ions bridged by three triazole ligands in a 1,2‐fashion. The coordination spheres of both iron ions are completed by two N CS anions and one monodentate triazole ligand. The monodentate triazole ligands are connected through the non‐coordinating N atom to the mononuclear iron unit by hydrogen bonds from its coordinated water molecule. Magnetic susceptibility measurements indicate a spin transition (ST) only for the iron ions in the dinuclear units, centred at around T 1/2 = 111 K. The transition takes place within a relatively narrow T range. The mononuclear iron ion remains in the high‐spin (HS) state even at very low temperature, yielding a ratio of 4:1 for the ST and HS iron ions. Temperature‐dependent Mössbauer spectroscopy confirms these results.