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On the Photomagnetism of Nitronyl Nitroxide, Imino Nitroxide, and Verdazyl-Substituted Azobenzene

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Title On the Photomagnetism of Nitronyl Nitroxide, Imino Nitroxide, and Verdazyl-Substituted Azobenzene
 
Creator DATTA, SN
PAL, AK
HANSDA, S
LATIF, IA
 
Subject INTRAMOLECULAR MAGNETIC INTERACTION
TRANSITION-METAL DIMERS
ELECTRONIC-SPECTRA
SPIN POLARIZATION
CRYSTAL-STRUCTURE
CIS-AZOBENZENE
HARTREE-FOCK
DIARYLETHENE
DIRADICALS
WAVEFUNCTIONS
 
Description The cis- and trans-azobenzenes are known as photochromic isomers with the trans- converting into the cis-form and vice versa upon irradiation with specific wavelengths. We have quantum chemically investigated the cis- and transforms of substituted azobenzene diradicals, with two nitronyl nitroxides, imino nitoxides, or verdazyls at para positions and serving as monoradical centers, to determine whether they can exhibit a photoassisted magnetic crossover. Geometries of both substituted and unsubstituted molecules have been optimized by density functional (DF) method UB3LYP using the 6-311G(d,p) basis set. Optimization of the geometry of the cis isomers has required special care. Single point singlet, triplet, and broken symmetry calculations have been done using 6-311++G(3df, 3pd) basis set. The magnetic exchange coupling constants have been estimated from the broken symmetry calculations. Absorption wavelengths have been estimated for both substituted and unsubstituted species from time-dependent DF treatment using restricted spin-polarized methodology RB3LYP and 6-311++G(3df, 3pd) basis set. From the similarity in the calculated absorption wavelengths for the unsubstituted and substituted azobenzenes, and the increased oscillator strengths (f) for the substituted species, we predict that the diradical isomers would be strongly photochromic. From our triplet state and broken symmetry calculations, we predict that both the cis- and the trans-diradicals are antiferromagnetically coupled. This prediction is consistent with the spin alternation rule, and the possibility of a magnetic crossover is nonexistent for these species.
 
Publisher AMER CHEMICAL SOC
 
Date 2014-10-16T14:55:25Z
2014-10-16T14:55:25Z
2012
 
Type Article
 
Identifier JOURNAL OF PHYSICAL CHEMISTRY A, 116(12)3304-3311
http://dx.doi.org/10.1021/jp3006537
http://dspace.library.iitb.ac.in/jspui/handle/100/15838
 
Language en