Theoretical study of cooperativity between hydrogen bond‒hydrogen bond, halogen bond‒halogen bond and hydrogen bond‒halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes

Abstract

ABSTRACTIn the present work, the cooperativity between hydrogen bond‒hydrogen bond, halogen bond‒halogen bond and hydrogen bond‒halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes is theoretically investigated. The sign of cooperative energy (Ecoop) obtained in all of the triads is positive which indicates that the ternary complex is less stable than the sum of the two isolated binary complexes. Moreover, our calculations show that Ecoop value in triads increases as FX…pyridazine…XF > FX…pyrimidine…XF > FX…pyrazine…XF. In agreement with energetic, geometrical and topological properties, electrostatic potentials and coupling constants across 15N…X−19F (X = 1H or 35Cl) hydrogen and halogen bonds indicate that hydrogen and halogen bonds are weakened in the considered complexes where two hydrogen and halogen bonds coexist. As compared to N…H hydrogen bond, it is also observed that cooperativity has greater effect on N…Cl halogen bond.