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submitted on 31.10.2019 and posted on 06.11.2019by Carlos Heras, Daniel Reta, Rosendo Valero, Guillermo Albareda, Nicholas Chilton, Alistair Fielding, Iberio de P. R Moreira, Josep Maria Bofill, Francisco Lopez Calahorra
The formation of stable organic biradicals by a deprotonation process is
reported for a series of conjugated heterocycles that share a
Ph-N(H)-2-thiazole structural motif. We characterise the
paramagnetic electronic ground state by means of continuous-wave and pulse EPR.
We propose a simple
valence bond mechanism for a deprotonation-induced formation of paramagnetic
organic molecules, based on the interplay between the electronegativity of
heteroatomic groups and the recovery of aromaticity to stabilise the biradical species. The Ph-N(H)-2-thiazole motif is found in a
variety of biologically active molecules, exemplified here with the anticancer
drug Dasatinib, and our results suggest a radical-based mechanism for the
protein kinase inhibition activity of the drug. The existence of this structure-property
relationship for an elementary chemical motif suggests that biradical species may be more prevalent than previously thought and have
an important role in bioorganic chemistry.