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Photoswitching Magnetic Crossover in Organic Molecular Systems

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Title Photoswitching Magnetic Crossover in Organic Molecular Systems
 
Creator SAHA, A
LATIF, IA
DATTA, SN
 
Subject DENSITY-FUNCTIONAL THEORY
FERROMAGNETICALLY COUPLED DIRADICALS
TRANSITION-METAL DIMERS
MIXED RADICAL CENTERS
NITRONYL NITROXIDE
CORRESPONDING ORBITALS
HARTREE-FOCK
SPIN STATES
DIARYLETHENE
BOND
 
Description We have theoretically designed efficient photomagnetic diradicals using both substituted and unsubstituted cyclophanediene (CPD) and dihydro-pyrenes (DHP) as spacers. Nitronyl nitroxide (NN), oxoverdazyl (o-VER), and tetrathiafulvalene (TTF) are chosen as monoradical centers. Molecular geometries have been optimized by the density functional method UB3LYP using the 6-311G (d,p) basis set. Final single point calculations have been done with the 6-311++G(d,p) basis. Absorption wavelengths have been estimated from time-dependent density functional treatment using restricted spin-polarized density functionals (RB3LYP) and 6-31G basis. Both the substituted and unsubstituted CPD species with mixed monoradical centers are found to be antiferromagnetically coupled. Diradicals with the same centers but with DHP coupler exhibit strong ferromagnetic coupling. Also, photoexcitations of the diradicals are generally red-shifted by only a few nanometers from those of the 15,16-dimethyl pyrenes. This indicates that on photoexcitation a consistent magnetic crossover from an antiferromagnetic to a ferromagnetic regime is possible. The accompanying change in magnetic exchange coupling constant Delta J is very large, varying from 445 to 1003 cm(-1). As far as organic molecular magnetism is concerned, this observation is entirely new and likely to be of technological significance.
 
Publisher AMER CHEMICAL SOC
 
Date 2012-06-26T09:01:46Z
2012-06-26T09:01:46Z
2011
 
Type Article
 
Identifier JOURNAL OF PHYSICAL CHEMISTRY A,115(8)1371-1379
1089-5639
http://dx.doi.org/10.1021/jp107049u
http://dspace.library.iitb.ac.in/jspui/handle/100/14248
 
Language English