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Theoretical and computational investigation of meta-phenylene as ferromagnetic coupler in nitronyl nitroxide diradicals

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Title Theoretical and computational investigation of meta-phenylene as ferromagnetic coupler in nitronyl nitroxide diradicals
 
Creator PAL, AK
MANERU, DR
LATIF, IA
MOREIRA, IDR
ILLAS, F
DATTA, SN
 
Subject Diradical
Magnetic coupling constant
DFT
Dihedral angle
Inductive effect
NICS(1)
DENSITY-FUNCTIONAL THEORY
INTRAMOLECULAR MAGNETIC INTERACTION
GROUND-STATE MULTIPLICITIES
INDEPENDENT CHEMICAL-SHIFTS
AB-INITIO CALCULATIONS
VALENCE-BOND THEORY
GEOMETRY OPTIMIZATION
ELECTRONIC-STRUCTURE
ORBITAL INTERACTIONS
CONJUGATED SYSTEMS
 
Description We predict the magnetic exchange coupling constant (J) for 27 m-phenylene-based nitronyl nitroxide (NN) diradicals with nine different substituents in three unique (common ortho, ortho-meta and common meta) positions on the coupler unit by using the broken-symmetry density functional methodology. For all investigated diradicals, J values are computed using B3LYP, B3LYP-D3 and M06-2X functionals with 6-311+G(d,p) basis set. The J (M06-2X) value is larger than J (B3LYP) and closer to the observed value for the unsubstituted species. Substitutions at common ortho position always produce a greater angle of twist between the spin source and the coupler units. When the twist angle is very large, the nature of intramolecular magnetic interaction changes from ferromagnetic to antiferromagnetic. In these cases, the coupler-NN bond order becomes small. Substitution at the common meta position of m-phenylene in the diradical has little steric and hydrogen-bonding effects. Electron-withdrawing groups reveal a specific trend for single-atom substitution. An ortho substitution generally decreases J and a meta substitution always increases J with a decreasing -I effect. Variation of J with planarity as well as Hammett constant is investigated. The nucleus-independent chemical shift value is found to decrease from the corresponding mono-substituted phenyl derivatives. The dependence of J on these factors is explored.
 
Publisher SPRINGER
 
Date 2014-12-28T11:48:59Z
2014-12-28T11:48:59Z
2014
 
Type Article
 
Identifier THEORETICAL CHEMISTRY ACCOUNTS, 133(4)
1432-881X
1432-2234
http://dx.doi.org/10.1007/s00214-014-1472-y
http://dspace.library.iitb.ac.in/jspui/handle/100/16400
 
Language English