Theoretical study on 5-nitrofuryl thiosemicarbazone radicals electronic properties

Theoretical studies of molecular conformations and electronic properties calculations of eight 5-nitrofuryl thiosemicarbazone free radicals, by means of ab initio (R/UHF), and DFT (R/UB3LYP) methods are presented and discussed in comparison with ESR and electrochemical experimental data. DFT calculated hyperfine coupling constants were used for the simulation of experimental spectra. We observed the molecules adopt mainly two conformations, both showing a pattern of spin density delocalization unusual for free radicals formed from aromatic nitrocompounds. Energy potential surfaces scaning through a determined dihedral angle were drawn to evaluate whether these conformations could coexist in equilibrium. Fukui and molecular orbital analysis were compared with ESR data as reactivity local indexes.