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Can Anisotropic Exchange Be Reliably Calculated Using Density Functional Methods? A Case Study on Trinuclear Mn-III-M-III-Mn-III (M=Fe, Ru, and Os) Cyanometalate Single-Molecule Magnets

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Title Can Anisotropic Exchange Be Reliably Calculated Using Density Functional Methods? A Case Study on Trinuclear Mn-III-M-III-Mn-III (M=Fe, Ru, and Os) Cyanometalate Single-Molecule Magnets
 
Creator SINGH, SK
RAJARAMAN, G
 
Subject cyanometalates
density functional calculations
magnetic properties
osmium
ruthenium
TRANSITION-METAL-COMPLEXES
EFFECTIVE CORE POTENTIALS
PRUSSIAN BLUE ANALOGS
HIGH BLOCKING TEMPERATURES
STATE PERTURBATION-THEORY
BETA-DIKETONE LIGAND
HIGH-SPIN MOLECULES
FE-III
BASIS-SETS
COORDINATION-COMPLEXES
 
Description Density functional studies have been performed on a set of trinuclear single-molecule magnets (SMMs) of general formula [{Mn-2(5-Brsalen)(2)(MeOH)(2)}M(CN)(6)](NEt4) (M=Fe-III (1), Ru-III (2) and Os-III (3); 5-Brsalen=N,N-ethylenebis(5-bromosalicylidene)iminato anion). We have computed the orbital-dependent exchange interaction for all three complexes for the first time using DFT and complete active space self-consistent field (CASSCF) methods. DFT calculations yield the anisotropic exchange as J=3.5cm(-1) for 1; J=12.1cm(-1), J=-6.9cm(-1) and J=-14cm(-1) for 2; and J=23.7cm(-1) and J=-11.1cm(-1) for 3. The computed values are in agreement with the experimental report, and this suggests that the established methodology can be used to compute the anisotropic exchange in larger clusters. Our calculations reiterate the fact that the exchange is described by a three-axis anisotropic exchange for complexes 2 and 3 as evidenced by the experiments. A stronger exchange coupling as we move down the periodic table from 3d to 5d is reproduced by our calculations, and the origin of this enhancement in the exchange interaction has been probed by using molecular orbital analysis. The electronic origin of different types of exchange observed in this series is found to be related to the energy difference between possible degenerate pairs and the nature of orbital interactions. By computing the exchange interaction, the single-ion anisotropy of Mn-III and zero-field splitting of the S=9/2 ground state of complexes 1-3 using CASSCF and/or DFT methods, we have attempted to shed light on the issue of anisotropic exchange and the barrier height for the magnetisation reversal in SMMs. Comprehensive magneto-structural correlations have been developed to offer clues on how to further enhance the barrier height in this class of SMMs.
 
Publisher WILEY-V C H VERLAG GMBH
 
Date 2014-12-28T12:39:56Z
2014-12-28T12:39:56Z
2014
 
Type Article
 
Identifier CHEMISTRY-A EUROPEAN JOURNAL, 20(1)113-123
0947-6539
1521-3765
http://dx.doi.org/10.1002/chem.201303489
http://dspace.library.iitb.ac.in/jspui/handle/100/16567
 
Language English