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Solid‐ and Solution‐State Studies of the Novel μ‐Dicyanamide‐Bridged Dinuclear Spin‐Crossover System {[(Fe(bztpen)] 2 [μ‐N(CN) 2 ]}(PF 6 ) 3 ⋅ n H 2 O
Author(s) -
OrtegaVillar Norma,
Thompson Amber L.,
Muñoz M. Carmen,
UgaldeSaldívar Víctor M.,
Goeta Andrés E.,
MorenoEsparza Rafael,
Real José A.
Publication year - 2005
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.200500171
Subject(s) - dicyanamide , crystallography , spin crossover , ethylenediamine , octahedron , spin transition , chemistry , crystal structure , spin states , ligand (biochemistry) , stereochemistry , inorganic chemistry , biochemistry , ionic liquid , receptor , catalysis
The mononuclear diamagnetic compound {Fe(bztpen)[N(CN) 2 ]}(PF 6 )CH 3 OH ( 1 ) (bztpen = N ‐benzyl‐ N , N ′, N ′‐tris(2‐pyridylmethyl)ethylenediamine) has been synthesized and its crystal structure studied. Complex 1 can be considered to be the formal precursor of two new dinuclear, dicyanamide‐bridged iron( II ) complexes with the generic formula {[(Fe(bztpen)] 2 [μ‐N(CN) 2 ]}(PF 6 ) 3 ⋅ n H 2 O ( n = 1 ( 2 ) or 0 ( 3 )), which have been characterized in the solid state and in solution. In all three complexes, the iron atoms have a distorted [FeN 6 ] octahedral coordination defined by a bztpen ligand and a terminal ( 1 ) or a bridging dicyanamide ligand ( 2 and 3 ). In the solid state, 2 and 3 can be considered to be molecular isomers that differ by the relative position of the phenyl ring of the two {Fe(bztpen)[N(CN) 2 ]} + halves ( cis and trans , respectively). Depending on the texture of the sample, 2 exhibits paramagnetic behavior or displays a very incomplete spin transition at atmospheric pressure. Complex 3 undergoes a gradual two‐step spin transition with no observed hysteresis in the solid state. Both steps are approximately 100 K wide, centered at ≈200 K and ≈350 K, with a plateau of approximately 80 K separating the transitions. The crystal structure of 3 has been determined in steps of approximately 50 K between 400 K and 90 K, which provides a fascinating insight into the structural behavior of the complex and the nature of the spin transition. Order–disorder transitions occur in the dicyanamide bridge and the PF 6 − ions simultaneously, with the spin‐crossover behavior suggesting that these transitions may trigger the two‐step character. In solution, 2 and 3 display very similar continuous spin conversions. Electrochemical studies of 2 and 3 show that the voltammograms are typical of dimeric systems with electronic coupling of the metals through the dicyanamide ligand.