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Solvate-Dependent Spin Crossover and Exchange in Cobalt(II) Oxazolidine Nitroxide Chelates

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Title Solvate-Dependent Spin Crossover and Exchange in Cobalt(II) Oxazolidine Nitroxide Chelates
 
Creator GASS, IA
TEWARY, S
RAJARAMAN, G
ASADI, M
LUPTON, DW
MOUBARAKI, B
CHASTANET, G
LETARD, JF
MURRAY, KS
 
Subject TRANSITION-METAL-COMPLEXES
GAUSSIAN-BASIS SETS
MAGNETIC INTERACTION
IRON(III) COMPLEX
CRYSTAL-STRUCTURE
RADICAL LIGANDS
ATOMS LI
COMPOUND
SYSTEMS
STATE
 
Description Two oxazolidine nitroxide complexes of cobalt(II), [Co-II(L-center dot)(2)]-(B (C6F5)(4))(2)center dot CH2Cl2 (1) and [Co-II(L-center dot)(2)](B(C6F5)(4))(2)center dot 2Et(2)O (2), where, L-center dot is the tridentate chelator 4,4-dimethy1-2,2-bis(2-pyridyl)oxazolidine N-oxide, have been investigated by crystallographic, magnetic, reflectivity, and theoretical (DFT) methods. This work follows on from a related study on [Co-II(L-center dot)(2)](-) (NO3)(2) (3), a multifunctional complex that simultaneously displays magnetic exchange, spin crossover, and single molecule magnetic features. Changing the anion and the nature of solvation in the present crystalline species leads to significant differences, not only between 1 and 2 but also in comparison to 3. Structural data at 123 and 273 K, in combination with magnetic data, show that at lower temperatures 1 displays low-spin Co(II)-to-radical exchange with differences in fitted J values in comparison to DFT (broken symmetry) calculated J values ascribed to the sensitive influence of a tilt angle (theta) formed between the Co(d(z)(2)) and the trans-oriented 0 atoms of the NO radical moieties in L-center dot Spin crossover in '1 is evident at higher temperatures, probably influenced by the solvate molecules and crystal packing arrangement. Complex 2 remains in the high-spin Co(II) state between 2 and 350 K and undergoes antiferromagnetic exchange between Co radical and radical radical centers, but it is difficult to quantify. Calculations of the magnetic orbitals, eigenvalue plots, and the spin densities at the Co and radical sites in 1 and 2 have yielded satisfying details on the mechanism of metal radical and radical radical exchange, the radical spins being in pi*(NO) orbitals.
 
Publisher AMER CHEMICAL SOC
 
Date 2014-12-28T12:24:36Z
2014-12-28T12:24:36Z
2014
 
Type Article
 
Identifier INORGANIC CHEMISTRY, 53(10)5055-5066
0020-1669
1520-510X
http://dx.doi.org/10.1021/ic5001057
http://dspace.library.iitb.ac.in/jspui/handle/100/16509
 
Language English