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Polyacene spacers in intramolecular magnetic coupling

DSpace at IIT Bombay

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Title Polyacene spacers in intramolecular magnetic coupling
 
Creator ALI, ME
DATTA, SN
 
Subject transition-metal-complexes
nitrophenyl nitronyl nitroxide
independent chemical-shifts
density-functional theory
broken symmetry approach
electron-spin-resonance
valence-bond theory
exchange interactions
imino nitroxide
aminoxyl radicals
 
Description We predict the intramolecular magnetic exchange coupling constant (J) for eleven nitronyl nitroxide diradicals (NN) with different linear and angular polyacene couplers from broken-symmetry density functional treatment. For the linear acene couplers, J initially decreases with increase in the number of fused rings. But from anthracene coupler onward, the J value increases with the number of benzenoid rings due to an increasing diradical character of the coupler moiety. The J value for the diradical with a fused bent coupler is always found to be smaller than that for a diradical with a linear coupler of the same size. The nuclear independent chemical shift (NICS) is calculated, and it is observed that the average of the NICS values per benzenoid ring in the diradical is less than that in the normal polyacene molecule. An empirical formula for the magnetic exchange coupling constant of a NN diradical with an aromatic spacer is obtained by combining the Wiberg bond order (BO), the angle of twist (phi) of the monoradical (NN) plane from the plane of the coupler, and the NICS values. A comparison of the formula with the computed values reveals that, from tetracene onward, the diradical nature of the linear acene couplers becomes prominent thereby leading to an increase in the ferromagnetic coupling constant. Isotropic hyperfine coupling constants are calculated by using a polarized continuum model for the diradicals in different solvents and in vacuum.
 
Publisher AMER CHEMICAL SOC
 
Date 2011-07-14T15:50:39Z
2011-12-26T12:49:03Z
2011-12-27T05:34:43Z
2011-07-14T15:50:39Z
2011-12-26T12:49:03Z
2011-12-27T05:34:43Z
2006
 
Type Article
 
Identifier JOURNAL OF PHYSICAL CHEMISTRY A, 110(49), 13232-13237
1089-5639
http://dx.doi.org/10.1021/jp0633594
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4001
http://hdl.handle.net/10054/4001
 
Language en