Hydrogen vs. halogen bonding in crystals of 2,5-dibromothiophene-3-carboxylic acid derivatives

• A series of 2,5-dibromothiophene-3-carboxylic acids derivatives was prepared. • X-ray structures of synthesized compounds determined and analyzed. • The competition between hydrogen and halogen bonding was revised. • Experimental data were supported via theoretical calculations. The competition between hydrogen (HB) and halogen (HaB) bonding in crystal structures of 2,5-dibromothiophene-3-carboxylic acid derivatives such as amides, esters, hydrazide and hydroxamic acid was studied by the analysis of both literature and newly obtained X-ray structures. It was found that the oxygen atom of carbonyl group either is involved in Br···O HaB or form NH···O HB with acidic protons of amide moieties and the latter interaction is more preferably. Theoretical calculations including topological analyses of the electron density distribution (QTAIM) and noncovalent interactions (NCI) approach were performed to prove the existence of these interactions and clarify their noncovalent nature.