On the performance of generalized valence bond theory in predicting magnetic exchange coupling constant in organic diradicals: A comparison with Hartree-Fock theory

We have investigated four different already synthesized meta- and para-connected diradicals to get their magnetic exchange coupling constants (1) through generalized valence bond (GVB) approach and also with Hartree-Fock (HF) theory with a view to establish the superiority of GVB method over HF theory for the prediction of J. In doing so, at first optimization of these molecules are done at B3LYP level of density functional theory using the 6-31++g(d) basis set. With these optimized geometries,J values are computed at GVB method along with TZV basis set and these values are compared with those of the J values obtained using HF/TZV level of theory. Nonetheless, J values found in both the theoretical processes are also compared with the experimental findings. Thus, the supremacy of the wavefunction based GVB method in predicting J is established in comparison with the HF method. (C) 2017 Elsevier B.V. All rights reserved.