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Spin Crossover in a Family of Iron(II) Complexes with Hexadentate ligands: Ligand Strain as a Factor Determining the Transition Temperature
Author(s) -
Matouzenko Galina S.,
Borshch Serguei A.,
Jeanneau Erwann,
Bushuev Mark B.
Publication year - 2009
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.200801852
Subject(s) - chemistry , spin crossover , ligand (biochemistry) , crystallography , amine gas treating , crystal structure , stereochemistry , spin transition , ring (chemistry) , organic chemistry , receptor , biochemistry
This paper reports the synthesis of a family of mononuclear complexes [Fe(L)]X 2 (X=BF 4 , PF 6 , ClO 4 ) with hexadentate ligands L=Hpy‐DAPP ({bis[ N ‐(2‐pyridylmethyl)‐3‐aminopropyl](2‐pyridylmethyl)amine}), Hpy‐EPPA ({[ N ‐(2‐pyridylmethyl)‐3‐aminopropyl][ N ‐(2‐pyridylmethyl)‐2‐aminoethyl](2‐pyridylmethyl)amine}) and Hpy‐DEPA ({bis[ N ‐(2‐pyridylmethyl)‐2‐aminoethyl](2‐pyridylmethyl)amine}). The systematic change of the length of amino‐aliphatic chains in these ligands results in chelate rings of different size: two six‐membered rings for Hpy‐DAPP, one five‐ and one six‐membered rings for Hpy‐EPPA, and two five‐membered rings for Hpy‐DEPA. The X‐ray analysis of three low‐spin complexes [Fe(L)](BF 4 ) 2 revealed similarities in their molecular and crystal structures. The magnetic measurements have shown that all synthesized complexes display spin‐crossover behavior. The spin‐transition temperature increases upon the change from six‐membered to five‐membered chelate rings, clearly demonstrating the role of the ligand strain. This effect does not depend on the nature of the counter ion. We discuss the structural features accountable for the strain effect on the spin‐transition temperature.