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A route to magnetically separable nanocatalysts: Combined experimental and theoretical investigation of alkyl substituent role in ligand backbone towards epoxidation ability
Author(s) -
Chattopadhyay Tanmay,
Chakraborty Aratrika,
Dasgupta Sanchari,
Dutta Arnab,
Menéndez M. Isabel,
Zangrando Ennio
Publication year - 2017
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.3663
Subject(s) - chemistry , catalysis , ligand (biochemistry) , schiff base , substituent , manganese , nanomaterial based catalyst , alkene , enantiomer , perchlorate , alkyl , medicinal chemistry , polymer chemistry , organic chemistry , ion , biochemistry , receptor
We have prepared two chiral Schiff base ligands, H 2 L 1 and H 2 L 2 , and one achiral Schiff base ligand, H 2 L 3 , by treating 2,6‐diformyl‐4‐methylphenol separately with ( R )‐1,2‐diaminopropane, ( R )‐1,2‐diaminocyclohexane and 1,1′‐dimethylethylenediamine, in ethanolic medium, respectively. The complexes MnL 1 ClO 4 ( 1 ), MnL 2 ClO 4 ( 2 ), MnL 3 ClO 4 ( 3 ), FeL 1 ClO 4 ( 4 ), FeL 2 ClO 4 ( 5 ) and FeL 3 ClO 4 ( 6 ) have been obtained by reacting the ligands H 2 L 1 , H 2 L 2 and H 2 L 3 with manganese(III) perchlorate or iron(III) perchlorate in methanol. Circular dichroism studies suggest that ligands H 2 L 1 and H 2 L 2 and their corresponding complexes have asymmetric character. Complexes 1 – 6 have been used as homogeneous catalysts for epoxidation of alkenes. Manganese systems have been found to be much better than iron counterparts for alkene epoxidation, with 3 as the best catalyst among manganese systems and 6 as the best among iron systems. The order of their experimental catalytic efficiency has also been rationalized by theoretical calculations. We have observed higher enantiomeric excess product with catalysts 1 and 4 , so they were attached to surface‐modified magnetic nanoparticles to obtain two new magnetically separable nanocatalysts, Fe 3 O 4 @dopa@MnL 1 and Fe 3 O 4 @dopa@FeL 4 . They have been characterized and their alkene epoxidation ability has been investigated. These catalysts can be easily recovered by magnetic separation and recycled several times without significant loss of catalytic activity. Hence our study focuses on the synthesis of a magnetically recoverable asymmetric nanocatalyst that finds applications in epoxidation of alkenes and at the same time can be recycled and reused.