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Triptycene‐Based, Carboxylate‐Bridged Biomimetic Diiron(II) Complexes
Author(s) -
Li Yang,
Soe Chan Myae Myae,
Wilson Justin J.,
Tuang Suan Lian,
Apfel UlfPeter,
Lippard Stephen J.
Publication year - 2013
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.201201387
Subject(s) - chemistry , benzoxazole , carboxylate , benzimidazole , triptycene , ligand (biochemistry) , crystallography , stereochemistry , metalation , square pyramidal molecular geometry , bioinorganic chemistry , medicinal chemistry , crystal structure , polymer chemistry , organic chemistry , biochemistry , receptor
A triptycene‐based bis(benzimidazole) ester ligand, L3 , was designed to enhance the electron‐donating ability of the heterocyclic nitrogen atoms relative to those of the first‐generation bis(benzoxazole) analogs, L1 and L2 . A convergent synthesis of L3 was designed and executed. Three‐component titration experiments using UV/Vis spectroscopy revealed that the desired diiron(II) complex could be obtained with a 1:2:1 ratio of L3 /Fe(OTf) 2 (MeCN) 2 /external carboxylate reactants. X‐ray crystallographic studies of two diiron complexes derived in this manner from L3 revealed their formulas to be [Fe 2 L3 (μ‐OH)(μ‐O 2 CR)(OTf) 2 ], where R = 2,6‐bis( p ‐tolyl)phenyl ( 7 ) or triphenylmethyl ( 8 ). The structures are similar to that of a diiron complex derived from L1 , [Fe 2 L1 (μ‐OH)(μ‐O 2 CAr Tol )(OTf) 2 ] ( 9 ), a notable difference being that, in 7 and 8 , the geometry at iron more closely resembles square‐pyramidal than trigonal‐bipyramidal. Mössbauer spectroscopic analyses of 7 and 8 indicate the presence of high‐spin diiron(II) cores. These results demonstrate the importance of substituting benzimidazole for benzoxazole for assembling biomimetic diiron complexes with syn disposition of two N ‐donor ligands, as found in O 2 ‐activating carboxylate‐bridged diiron centers in biological systems.