J. Chem. Sci. Ó (2020) 132:18 Indian Academy of Sciences https://doi.org/10.1007/s12039-019-1715-5 Sadhana(0123456789().,-volV)FT3](0123456789().,-volV) REGULAR ARTICLE Substituent effects on the halogen and pnictogen bonds characteristics in ternary complexes 4-YPhNH2ÁÁÁPH2FÁÁÁClX (Y = H, F, CN, CHO, NH2,CH3,NO2 and OCH3, and X = F, OH, CN, NC, FCC and NO2): A theoretical study TAHEREH TONDRO and HOSSEIN ROOHI* Department of Chemistry, Faculty of Science, University of Guilan, Rasht, Iran E-mail: [email protected]; [email protected] MS received 17 May 2019; revised 23 August 2019; accepted 1 September 2019 Abstract. The synergistic relationship between pnictogen and halogen non-covalent interactions in 4-YPhNH2ÁÁÁPH2FÁÁÁClX (Y = H, F, CN, CHO, NH2,CH3,NO2 and OCH3; X = F, OH, CN, NC, FCC and NO2) complexes were explored using Aug-ccpVDZ basis set and M06-2X and M06-2X-GD3, B2PLYP-GD3 and mPW2PLYP-GD2 functionals. The effects of the substituents included at pnictogen bond and halogen bond segments on the correlation between BEs and pnictogen as well as halogen bond distances, electron density at both non-covalent interactions, charge transfer energies between components and the NMR properties were evaluated. The energy analysis indicates that the pnictogen bond interaction has a much greater stabilizing effect than the halogen bond one. In addition, the auxiliary effect of a pnictogen bond on a halogen bond is more pronounced than that of a halogen bond on a pnictogen bond. Keywords. Cooperative effect; pnictogen bond; halogen bond; dispersion; substitution effect. 1. Introduction chemistry,53–55 formation of eutectic molecular liquids (EMLs),56 interstellar chemistry57 to biological The noncovalent interactions play an essential role in recognition processes.11,58 The pnictogen and halogen 1–20 intermolecular and intramolecular interactions. bonds can be verified experimentally by using X-ray The cooperativity between two non-covalent interac- diffraction,33,47,59,60 terahertz spectroscopy,49 IR and 21 tions of the same type such as hydrogen bonds, Raman,47,61 and NMR47,62 spectroscopies. 22–24 25 halogen bonds, pnictogen bonds, and different Li et al., have reported significant cooperative 26–31 combinations with other r-hole interactions are effects between non-covalent pnictogen and halogen the subject of many research works. 3 interactions in XClÁÁÁFH2PÁÁÁNH3 complex systems. The interest in the study of pnictogen bond inter- They have also studied the cooperative effects 32,33 actions has grown both experimentally and theo- between lithium and halogen bond interactions in 5,33–44 retically. Most of the confirmation for pnictogen MCNÁÁÁLiCNÁÁÁXCCH (M = H, Li, and Na; X = Cl, bonds arose initially from crystal structure analy- Br, and I) complexes.63 The positive cooperativity 45–48 ses. The pnictogen bonds containing phosphorus, between pnictogen bond and anion-p interactions, the in particular, have been an area of increasing interest cationic-p interactions and pnictogen bonds were over the past years due to their potential roles in the studied by Esrafili et al. 64 and Li et al.,30 respectively. 49–52 medicinal chemistry and biological systems. In The substituent effects in cationic pnictogen bonded ? addition to expanding scientific knowledge frontiers, complexes between XH3P and NCY molecules the experimental chemists can use the results of the- (X = H, F, CN, NH2 and OH; Y = H, Li, F, Cl) were oretical approaches in the wide-ranging interest from explored by Esrafili et al.65 These authors also studied the crystal engineering and supermolecular the cooperativity between conventional (LiÁÁÁN/C) and *For correspondence Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s12039-019-1715-5) contains supplementary material, which is available to authorized users. 18 Page 2 of 21 J. Chem. Sci. (2020) 132:18 non-conventional (LiÁÁÁp) lithium interactions in The interaction energies are corrected for basis set NCLiÁÁÁNCLiÁÁÁXCCX and CNLiÁÁÁCNLiÁÁÁXCCX superposition error (BSSE) using the standard coun- 66 (X = H, F, Cl, Br, OH, CH3, and OCH3) complexes. terpoise correction (CP) method proposed by Boys and The effect of substituents on the cooperativity between Bernardi.76 The dispersion corrected M06-2X-GD3, fluorine centered halogen bonds in NCFÁÁÁNCFÁÁÁNCX B2PLYP-GD3 and mPW2PLYP-GD2 functionals and CNFÁÁÁCNFÁÁÁCNX complexes (X = H, F, Cl, CN, were also used to calculate the BEs.77,78 67 OH and NH2) was investigated by Esrafili et al. In The topological analyses of the electronic charge another study, the cooperative effects between non- density for all complexes were performed using covalent interactions of pnictogen and dihydrogen Bader’s QTAIM theory79 andbymeanofAIM2000 bond types have been propounded by Esrafili et al., in software.80 The natural bond orbital (NBO) analy- 81 HMHÁÁÁHCNÁÁÁPH2X (X = H, F, Cl and M = Be, Mg, sis was performed by using the wave functions Zn) complexes.68 These authors also examined the obtained at the M06-2X/aug-ccpVDZ level of cooperativity of pnictogen bonds in XH2PÁÁÁNCH2- theory. PÁÁÁNCY (X = F, Cl; Y = H, F, CN, OH, NH2) com- The electrophilic and nucleophilic sites in a mole- plexes.69 Also, Esrafili et al.,70 have investigated the cule can be recognized by the molecular electrostatic unusual cooperativity effects between halogen bond potential (MESP) topography analysis. The electro- and donor-acceptor interactions in the C5H5- static potential V(r) is a three-dimensional local BÁÁÁNCXÁÁÁNCY complexes, where X = F, Cl, Br, I, property that can be evaluated at any or all points r in P qðÞr0 r0 ZA d and Y = H, CN, OH, Li. VrðÞ¼ À r 0 the space of a system by jRAÀrj jr Àrj in In the previous work, we have explored the A pnictogen bond non-covalent interactions in terms of atomic units, au. The ZA is the charge on - 4-XPhNH2:PFnH3-n complexes (n = 1–3, X = H, F, nucleus A, located at RA;|RA r| represents its dis- 71 - CN,CHO,NH2,CH3,NO2 and OCH3). In the tance from r, just as |r’ r| is the distance of each current work, the non-covalent pnictogen and halo- electronic charge increment -eq(r’)dr’ from r. The gen bond (PB and HB) interactions in ternary V(r) may be either positive or negative in any given complexes 4-YPhNH2ÁÁÁPH2FÁÁÁClX(Y=H,F,CN, region, depending upon whether the effect of the 82 CHO, NH2,CH3,NO2 and OCH3 and X = F, OH, nuclei or the electrons is dominant there. The CN, NC, FCC and NO2) were investigated. The MESPs on the 0.001 au contours were calculated at the substituent effects on cooperativity between pnic- M06-2X/aug-cc-pVDZ level with the Multiwfn 83 togen and halogen bonds were taken into account. program. 31 r Binding energies (BEs), structural characteristics, The absolute P chemical shielding isotropy ( iso), charge transfer energies, Wiberg bond indexes, as well as the spin-spin coupling constant across the electron density properties, 31P chemical shielding pnictogen bond, were calculated at the M06-2X/aug- and 31PÁÁÁ15N spin-spin coupling constants of the cc-pVDZ level of theory employing gauge included 84 ternary complexes were determined and analyzed. atomic orbital (GIAO) approach. To understand the mechanism of synergetic effects The energy decomposition analysis (EDA) was and dependence of cooperative effects on sub- carried out at BP86–D3/TZ2P(ZORA)//M06-2X/ stituent, the natural bond orbital (NBO) theory, aug-ccpVDZ level using the ADF 2009.01 program molecular surface electrostatic potential (MESP) package. EDA calculations were carried out in order analysis, atoms in molecules (AIM) theory, and to analyze the nature of the pnictogen and halogen energy decomposition analysis (EDA) were utilized. bonds interactions. Here, the interaction energy The structures of complexes studied are depicted in between the interacting fragments (4-YPhNH2, Figure 1. PH2F and ClX) was divided into four terms as shown in Eq. 1. D ¼ D þ D þ D þ D ; ð Þ 2. Computational methods Eint Eelstat EPauli Eorb Edisp 1 D D D D All calculations were carried out using the Gaussian where the Eelstat, EPauli, Eorb and Edisp are the package.72 The geometries for all of the monomers, electrostatic interaction, Pauli repulsion, orbital inter- dimers and trimers were optimized at M06-2X/aug-cc- action and the dispersion energy between two inter- pVDZ level of theory. The suitability of the M06-2X acting fragments, respectively. density functional method for the study of non-cova- Equations 2, 3, 4 and 5 were used for calculation of lent interactions has been described previously.73–75 the -BE (interaction energies) of the pnictogen bonds J. Chem. Sci. (2020) 132:18 Page 3 of 21 18 Y Y H P H H N F H N H H Cl X H P H P H H F F Cl X a b c Figure 1. Structures of the studied dimers and trimers. (a) 4-YPhNH2ÁÁÁPH2F (b) PH2FÁÁÁClX (c) 4- YPhNH2ÁÁÁPH2FÁÁÁClX (X = F, OH, CN, NC, FCC and NO2 and Y = H, F, CN, CHO, NH2,CH3,NO2 and OCH3). in dimers (Eint,AB), halogen bonds in dimers (Eint,BC), Finally, the cooperative energy in the trimer com- pnictogen bonds in trimers (Eint,AB(T)) and halogen plexes could be achieved by using the following Eq. 10: bonds in trimers (Eint,BC(T)), respectively. ÀÁ Ecoop ¼ Eint;ABCÀ Eint;AB þ Eint;BC þ Eint;ACðTÞ ð10Þ Eint;AB ¼ EABÀðÞEA þ EB ð2Þ Eint;BC ¼ EBCÀðÞEB þ EC ð3Þ ÀÁ3. Results and Discussion Eint;ABðTÞ ¼ EABC À EA þ EBC þ Eint;ACðTÞ ð4Þ ÀÁ3.1 Molecular electrostatic potential (MESP) Eint;BCðTÞ ¼ EABC À EC þ EAB þ Eint;ACðTÞ ð5Þ analysis Where, EAB,EBC,EA,EB,EC are the total energies of MESP is a real physical experimental property that the optimized dimers and monomers.