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Field‐Induced Slow Magnetic Relaxation in a Mononuclear Manganese(III)–Porphyrin Complex
Author(s) -
PascualÁlvarez Alejandro,
Vallejo Julia,
Pardo Emilio,
Julve Miguel,
Lloret Francesc,
Krzystek J.,
Armentano Donatella,
Wernsdorfer Wolfgang,
Cano Joan
Publication year - 2015
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.201502637
Subject(s) - manganese , chemistry , crystallography , denticity , electron paramagnetic resonance , tetraphenylporphyrin , relaxation (psychology) , porphyrin , ligand (biochemistry) , ion , single crystal , zero field splitting , ligand field theory , nuclear magnetic resonance , crystal structure , electron , photochemistry , spin polarization , physics , psychology , social psychology , biochemistry , receptor , organic chemistry , quantum mechanics
Abstract We report on a novel manganese(III)–porphyrin complex with the formula [Mn III (TPP)(3,5‐Me 2 pyNO) 2 ]ClO 4 ⋅CH 3 CN ( 2 ; 3,5‐Me 2 pyNO=3,5‐dimethylpyridine N ‐oxide, H 2 TPP=5,10,15,20‐tetraphenylporphyrin), in which the Mn III ion is six‐coordinate with two monodentate 3,5‐Me 2 pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in 2 is responsible for the large and negative axial zero‐field splitting ( D =−3.8 cm −1 ), low rhombicity ( E /| D |=0.04) of the high‐spin Mn III ion, and, ultimately, for the observation of slow magnetic‐relaxation effects ( E a =15.5 cm −1 at H =1000 G) in this rare example of a manganese‐based single‐ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single‐crystal diffraction studies, variable‐temperature direct‐ and alternating‐current measurements and high‐frequency and ‐field EPR spectroscopic analysis followed by quantum‐chemical calculations. Slow magnetic‐relaxation effects were also observed in the already known analogous compound [Mn III (TPP)Cl] ( 1 ; E a =10.5 cm −1 at H =1000 G). The results obtained for 1 and 2 are compared and discussed herein.