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Quantum Chemical Investigation of meta-Xylylene Based One-Dimensional Polymer Chain

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Title Quantum Chemical Investigation of meta-Xylylene Based One-Dimensional Polymer Chain
 
Creator PAL, AK
HANSDA, S
DATTA, SN
 
Subject DENSITY-FUNCTIONAL THEORY
NITRONYL NITROXIDE DIRADICALS
SPIN ORGANIC-MOLECULES
HARTREE-FOCK
GROUND-STATE
HYDROCARBON DIRADICALS
EXCHANGE INTERACTIONS
M-PHENYLENE
AB-INITIO
TRIPLET
 
Description We have investigated unsubstituted and methyl substituted polyradical chains of meta-xylylene by using density functional theory-broken symmetry methodology (DFT-BS). Optimization of geometry in the high-spin and low-spin states have been done at B3LYP/6-31G(d,p) and M06-2X/6-31G(d,p) levels in unrestricted methodology. Single-point calculations on the high-spin optimized geometries have been done by using the 6-311G(d,p) basis set. Each polyradical has been found to be nonplanar with a high-spin ground state. Each has a coupling constant larger than thermal energy. For each group of polyradicals, the coupling constant has been found to exponentially decrease with increase in the number of phenylene groups. The B3LYP infinite chain limit has been estimated for both the unsubstituted and substituted polyradicals. The individual inter-radical-site coupling constants have been estimated for the triradicals and tetraradicals using HDVV Hamiltonian in ORCA 3.0.1 code. These are also generally large and positive, revealing a strong intersite ferromagnetic interaction. The intersite coupling constant too decreases with increasing distance between the radical centers. Finally, we have used CRYSTAL09 package for calculations on the infinitely long one-dimensional and periodic polyradical chains. The coupling constants estimated from the periodic calculations are quite large at about 500 cm(-1) and somewhat greater than the limiting values calculated for the polyradicals with an increasing number of phenylene groups. This happens as the individual polyradicals of increasing size progressively deviate from periodicity, and thereby lessens the strength of through-bond spin-spin coupling. The calculated band gap of similar to 4.5 eV indicates that the infinitely long one-dimensional chains must be ferromagnetic and electron insulators.
 
Publisher AMER CHEMICAL SOC
 
Date 2016-01-15T06:08:47Z
2016-01-15T06:08:47Z
2015
 
Type Article
 
Identifier JOURNAL OF PHYSICAL CHEMISTRY A, 119(10)2176-2185
1089-5639
http://dx.doi.org/10.1021/acs.jpca.5b01081
http://dspace.library.iitb.ac.in/jspui/handle/100/17894
 
Language en