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Mossbauer Study of the Effect of Intraligand Substituents on the Spin Crossover in Solid (Dithiocyanato) BIS ( N ‐Substituted‐Phenyl‐2‐Pyridinaldimine) Iron (II)
Author(s) -
Wei H.H.,
Kao S.P.
Publication year - 1985
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.198500062
Subject(s) - chemistry , substituent , spin crossover , ring (chemistry) , spin transition , polar effect , mössbauer spectroscopy , crystallography , medicinal chemistry , spin (aerodynamics) , spin states , inorganic chemistry , organic chemistry , engineering , aerospace engineering
The spin transition of high‐spin ( s T 2 ⇄ )low‐spin ( 1 A 1 ) of (dithiocyanato) ( N ‐phenyl‐2‐pyridinaldimine) iron (II) complexes can be altered by substituents on the phenyl ring. Mössbauer spectra at 78 K for the 4‐substituted derivatives (with the exception of the 4‐OH‐substituted derivative) indicate that the fraction of low‐spin states increases with decreasing substituent electron‐withdrawing ability, as measured by the Hammet σ constant (4‐OCH 3 <4‐CH 3 CONH 4‐C 6 H 5 <4‐CH 3 <4‐H<4‐Cl<4‐NO 2 ). In addition, the effect of methyl‐substitution at the ortho‐, meta‐ or paraposition of the phenyl ring on the spin transition was examined. Mössbauer spectra of these methyl‐substituted complexes reveal quite different spin equilibria.