Competition between hydrogen bonds and halogen bonds in complexes of formamidine and hypohalous acids

Abstract

Quantum chemical calculations have been per-formed for the complexes of formamidine (FA) and hypohalous acid (HOX, X = F, Cl, Br, I) to study their structures, properties, and competition of hydrogen bonds with halogen bonds. Two types of complexes are formed mainly through a hydrogen bond and a halogen bond, respectively, and the cyclic structure is more stable. For the F, Cl, and Br complexes, the hydrogen-bonded one is more stable than the halogen-bonded one, while the halogen-bonded structure is favorable for the I complexes. The associated H-O and X-O bonds are elongated and exhibit a red shift, whereas the distant ones are contracted and display a blue shift. The strength of hydrogen and halogen bonds is affected by F and Li substitutents and it was found that the latter tends to smooth differences in the strength of both types of interactions. The structures, properties, and interaction nature in these complexes have been understood with natural bond orbital (NBO) and atoms in molecules (AIM) theories.

Interplay between N∙∙∙H, N∙∙∙X and π∙∙∙X interactions in the complex pairing of pyrazine with hypohalous acids: A NBO and QTAIM (quantum theory of atoms in molecules) analysis

“…The H···N distance in PZ:HOF A-HB (X = Cl, Br and I) complexes. It is in line with its stability and t demonstrated in the HB complexes of hypohalous acids previously [39,48]. This might be attributed to the nature of O-X bonds, since O O-X bonds are of electron donor the valence shell of oxygen [19,49].…”

“…The H···N distance in PZ:HOF-A-HB is longer than other PZ:HOX = Cl, Br and I) complexes. It is in line with its stability and this subject has been demonstrated in the HB complexes of hypohalous acids previously [39,48]. This might be X bonds, since O-F bond is a covalent, polarized bond, while other X bonds are of electron donor-acceptor-type with the halogen donating electron density to the valence shell of oxygen [19,49].…”

“…For es could be optimized. The interaction energy is a HOX (X = F, Cl, Br and I) at the HB (X = F, = I the B. Hydrogen bonding in HB complexes were not influenced by X atom, considerably, thus their stabilization HB is longer than other PZ:HOXhis subject has been demonstrated in the HB complexes of hypohalous acids previously [39,48]. This might be F bond is a covalent, polarized bond, while other the halogen donating electron density to the valence shell of oxygen [19,49].…”

A Protein Data Bank Survey Reveals Shortening of Intermolecular Hydrogen Bonds in Ligand-Protein Complexes When a Halogenated Ligand Is an H-Bond Donor

“…These values agree with energies estimated by IR spectroscopy, for CF 3 -X•••N(CH 3 ) 3 in liquid noble gases, which are the best models for a non-polar solvent that does not interfere with solute-solute interactions: 2.1, 4.4 and 6.8 kcal/mol for X-bonds involving Cl, Br and I, respectively [31]–[33]. These halogen bonds can compete with hydrogen bonding, as well documented for numerous low-mass complexes in silico [34], [35], in solution [36], [37], and in the solid state [17], [38], [39].…”

On the nature of halogen bonded complexes between carbonyl bases and chlorotrifluoromethane

“…Let us remember that halogen bonds have been compared to hydrogen bonds and have been shown to be similar in many aspects [63][64][65][66][67]. Briefly summarizing, let us mention that the contraction of a Z-H bond in a hydrogenbonded system ZH···Y has been explained mainly by a variation of the σ*(C-H) occupation and a change in the hybridization of the Z(H) atom [68][69][70][71][72][73][74].…”