Intermolecular Interactions Between Halo-Cyclopropenone Derivatives

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The intermolecular interactions between halo-cyclopropenone derivatives (HC3OX;X= F, Cl, Br and I) and hypohalous acids (HOY; Y=F, Cl, Br and I) were investigated using the MP2 method with aug–cc-pVTZ basis set. Three types of complexes are forming by:1) hydrogen bond, 2) both hydrogen and halogen bonds, 3) halogen bond interactions. The results indicated that interactions in type 1 complexes are stronger than those in types 2 and 3. The H–O bonds show red shifts with complex formation in types 1 and 2, in which they are more considerable for type 1 complexes. The O–Y bonds display red shifts in the type 3 and blue shift in the type 2 complexes. Molecular electrostatic potential (MEP), quantum theory of atoms in molecules (QTAIM)

The graphical illustration of the representative configurations under consideration is depicted in Figure 2. Possible interactions which considered for HOY molecules with HC3OX are including hydrogen bonding (O···H) and halogen bonding (X···Y,O···X) which have been denoted as XYm. The X is representing the cyclopropenone (HC3OF, HC3OCl, HC3OBr, and HC3OI were defined as F, Cl, Br and I, respectively); Y shows the HOY molecules (HOF, HOCl, HOBr, and HOI were defined as F, Cl, Br and I, respectively) and m was applied for displaying the type of complex that formed between them. For example FI1 shows type 1 complex of HC3OF with HOI or BrBr2 is illustrating type 2 complex of HC3OBr with HOBr. The XY1 type shows O···H interactions, which HOY acts as hydrogen bond donor (HBD). In the XY2 type, the O···H and X···Y interactions have been assigned between HOY and HC3OX molecules. In the H···O interaction HOY acts as HBD while in the X···Y it might act as electron acceptor (Lewis acid) or electron donor (Lewis base) regarding the nature of X and Y atoms. In the XY3 model a halogen bond (XB) interaction was found between HC3OX and HOY in which Y atom of HOY as electron acceptor interact with O atom of HC3OX as electron donor. It should be noted that no halogen bond was observed between HC3OX and HOF (FF3, ClF3, BrF3 and IF3). The intermolecular distances for complexes and the bond lengths difference between complexes and isolated monomers are listed in Table 1. The O···H (Types 1 and 2), X···Y and O···Y distances are in the ranges of 1.762–1.809 Å, 1.746–1.823 Å, 3.064–4.182 Å, and 2.610–2.697 Å, respectively. The calculated intermolecular distances for O···H (Types 1 and 2) and O···Y are less than the sum of the van der Waals (vdW) radii of the corresponding atoms (vdW radii for H, O, F, Cl, Br and I are 1.20, 1.52, 1.47 , 1.75, 1.85 and 1.98 Å, respectively [40]), indicating attractive