Antiradical capacity of a series of organotin(IV) compounds: A chemical reactivity study in the Density Functional Theory framework

Here we explore in the Density Functional Theory (DFT) framework the antiradical activity of picolinic (PA), nicotinic (NA) and isonicotinic (INA) acids and a group of derivative stannoxanes of the type RC(O)OSnX3. Using the single charge transfer model proposed by Gázquez et al. (electrodonating ω− and electroaccepting ω+ powers), a Donor Acceptor Map (DAM) was employed to classify them as good or bad antiradicals. In the case of acids, an antiradical activity behavior was measured for each bond position of the –COOH functional group at the pyridine ring. For esters, antiradical activity was calculated considering three types of ligands: n-butyl, phenyl and the above acids. Esters showed a better antiradical behavior as electron donors than their corresponding acids. Two esters derived from picolinic acid showed a good donor index (Rd), which was closed to Rd of vitamin C, all above in their neutral form. In this assessment, the analytic Fukui function isosurface f− was included in order to determinate those regions of our molecules where it is most likely to occur the interaction with a free radical. The Fukui function f− was located mainly at the N atom of the pyridine ring for the three acids and most of the esters.