Theoretical study on the interactions of halogen‐bonds and pnicogen‐bonds in phosphine derivatives with Br₂, BrCl, and BrF

Abstract

The MP2 ab initio quantum chemistry methods were utilized to study the halogen-bond and pnicogen-bond system formed between PH 2 X (X 5 Br, CH 3 , OH, CN, NO 2 , CF 3 ) and BrY (Y 5 Br, Cl, F). Calculated results show that all substituent can form halogen-bond complexes while part substituent can form pnicogen-bond complexes. Traditional, chlorine-shared and ion-pair halogenbonds complexes have been found with the different substituent X and Y. The halogen-bonds are stronger than the related pnicogen-bonds. For halogen-bonds, strongly electronegative substituents which are connected to the Lewis acid can strengthen the bonds and significantly influenced the structures and properties of the compounds. In contrast, the substituents which connected to the Lewis bases can produce opposite effects. The interaction energies of halogen-bonds are 2.56 to 32.06 kcalÁmol 21 ; The strongest halogen-bond was found in the complex of PH 2 OH···BrF. The interaction energies of pnicogen-bonds are in the range 1.20 to 2.28 kcalÁmol 21 ; the strongest pnicogen-bond was found in PH 2 Br···Br 2 complex. The charge transfer of lp(P) Ar*(BrAY), lp(F) Ar*(BrAP), and lp(Br) Ar*(XAP) play important roles in the formation of the halogen-bonds and pnicogen-bonds, which lead to polarization of the monomers. The polarization caused by the halogen-bond is more obvious than that by the pnicogen-bond, resulting in that some halogenbonds having little covalent character. The symmetry adapted perturbation theory (SAPT) energy decomposition analysis showes that the halogen-bond and pnicogen-bond interactions are predominantly electrostatic and dispersion, respectively. K E Y W O R D Sab initio calculation, halogen-bond, interaction energy, pnicogen-bond, symmetry adapted perturbation theory 1 | I N TR ODU C TI ON Noncovalent interactions often play an important role in the stabilization of macromolecular, such as proteins and nucleic acids. Typically, noncovalent interactions include van der Waals forces, electrostatic interactions, hydrophobic interactions, and hydrogen bonds, in which the hydrogen bonding has been extensively investigated partially due to its high importance in systems involving water molecules. There are still some other types of noncovalent bonding, such as halogen bonding and lithium bonding. [1] These interactions have some similarities to the hydrogen bonding, but the details are not very clear and much effort has been put into revealing the nature of these interactions during the past decades. In our previous Int J Quantum Chem. 2017;117:e25443.

Exploring Nature and Predicting Strength of Hydrogen Bonds: A Correlation Analysis Between Atoms‐in‐Molecules Descriptors, Binding Energies, and Energy Components of Symmetry‐Adapted Perturbation Theory

“…For example, the coupled cluster of singles and doubles with perturbative triples correction, such as CCSD(T), is able to calculate very accurate BE values with mean absolute deviation (MAE) of chemical accuracy (1 kcal/mol) or even better . In addition, the symmetry‐adapted perturbation theory (SAPT) is not only able to evaluate BE but also capable of decomposing the BE into various physical components to facilitate the understanding of the nature of the interactions.…”

Comparison between Chlorine-Shared and π–Halogen Bonds Involving Substituted Phosphabenzene and ClF Molecules

“…Jiao et al predicted an interaction energy ranging between −7.32 and −25.18 kJ mol –1 for the XH 2 P···BrF complexes (X = OH, CH 3 , Br, NO 2 , CF 3 , CN) calculated at the CCSD(T)/aug-cc-pVTZ level. 15 The binding energy for the present XC 5 H 4 P·ClF complexes is much higher than that of the XH 2 P·BrF complexes. Interestingly, the binding strength of the PPBZ·ClF complex is much lower than the previously reported binding strength of the PH 3 .ClF complex (−51.2 kJ mol –1 ).…”

“… 43 , 44 For the same complexes between PH 2 X with BrCl and BrF, the H ( r c ) values were found to be all negative ranging between −0.0188 and −0.1452 a.u., indicating the presence of partial covalent character. 15 Similarly, for the T1-X-PPBZ·ClF complexes, the H ( r c ) values are found to be negative, ranging between −0.0538 and −0.062 a.u. Moreover, the values of ratio G ( r c )/ρ( r c ) are less than 1 for all the complexes.…”

“…of the recently studied halogen-bonded complexes between PH 2 X with BrCl and BrF. 15 The ρ( r c ) value for a pure covalent P–Cl bond in PCl 3 is found to be 0.1317 a.u., indicating that the P···Cl bond in T1-X-PPBZ·ClF complexes is highly covalent in nature. In various recent works on noncovalent interactions, H ( r c ) and the ratio G ( r c )/ρ( r c ) were used as indicators in predicting whether an interaction is predominantly covalent or electrostatic.…”

“…Jiao et al recently studied the traditional, chlorine-shared, and ion pair halogen-bonded complexes between various phosphine derivates and mixed halogens like Br 2 , BrCl, and BrF. 15 Alkorta et al studied the halogen-bonded complexes between XCP and ClF and classified them based on two different configurations: one forming through the FCl···P halogen bond and the other when ClF interacts with the C≡P triple bond through a perturbed π system. 17 They further showed that the nature of the halogen bond changes from traditional to chlorine-shared and the interaction energies increase, as the electron-donating ability of X increases in XCP···ClF complexes.…”