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Unconventional Spin Crossover in Dinuclear and Trinuclear Iron(III) Complexes with Cyanido and Metallacyanido Bridges
Author(s) -
Šalitroš Ivan,
Boča Roman,
Dlháň L'ubor,
Gembický Milan,
Kožíšek Jozef,
Linares Jorge,
Moncol' Ján,
Nemec Ivan,
Perašínová Lucia,
Renz Franz,
Svoboda Ingrid,
Fuess Hartmut
Publication year - 2009
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.200900169
Subject(s) - chemistry , spin crossover , crystallography , antiferromagnetism , salicylaldehyde , valence (chemistry) , spin states , spin transition , stereochemistry , inorganic chemistry , schiff base , condensed matter physics , organic chemistry , physics
A nonsymmetrical triamine, 1,6‐diamino‐4‐azahexane, was Schiff‐condensed with (X‐substituted) o ‐salicylaldehyde to yield pentadentate ligands X‐L 5 : salpet and MeBu‐salpet. These ligands form mononuclear, dinuclear, and trinuclear Fe III complexes, whose structures were determined by single‐crystal X‐ray analysis. Of the mononuclear complexes, [Fe III (salpet)Cl] and [Fe III (MeBu‐salpet)Cl] are high spin ( S = 5/2), whereas [Fe III (salpet)CN] · MeOH is low spin ( S = 1/2). The dinuclear and trinuclear complexes show a kind ofthermally induced spin crossover. The dinuclear complex [L 5 Fe III (CN)Fe III L 5 ](ClO 4 ) · 2H 2 O (L 5 = salpet) is a mixed‐spin assembly: the C ‐coordinated Fe III center is low spin (L) and the N ‐coordinated Fe III center is high spin (H) at low temperature; an antiferromagnetic interaction occurs between them. This LH reference state is mixed with the LL one. Upon heating, the system shows an increasing content of the HH state. Also, the dinuclear complex [L 5 Fe III (CN)Fe III L 5 ](BPh 4 ) · 2MeCN (L 5 = MeBu‐salpet) exhibits a spin transition between LH and HH spin pairs. The mixed‐valence trinuclear complex [L 5 Fe III {Fe II (CN) 5 (NO)}Fe III L 5 ] · 0.5MeOH · 3.75H 2 O (L 5 = salpet) shows spin crossover with a residual high‐spin fraction at liquid He temperature owing to the LL + LH ground state. The metallacyanido‐bridged complex [L 5 Fe III {Ni(CN) 4 }Fe III L 5 ] · 2MeOH (L 5 = MeBu‐salpet) contains a high‐spin pair, HH, over the whole temperature interval with a ferromagnetic exchange interaction. A theoretical model was outlined that allows simultaneous fitting of all available experimental data (magnetic susceptibility, magnetization, high‐spin mole fraction obtained from the Mössbauer spectra) on a common set of parameters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)