Effects of Lewis Basicity and Acidity on σ-Hole Interactions in Carbon-Bearing Complexes: A Comparative Ab Initio Study

The effects of Lewis basicity and acidity on σ-hole interactions were investigated using two sets of carbon-containing complexes. In Set I, the effect of Lewis basicity was studied by substituting the X3/X atom(s) of the NC-C6H2-X3 and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F3 and F-C-X3 (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centers. Concerning the Lewis basicity effect, higher negative interaction energies (Eint) were observed for the F-C-F3∙∙∙NC-C6H2-X3 complexes compared with the F-C-F3∙∙∙NCX analogs. Moreover, significant Eint was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X3/X atom(s). Among Set I complexes, the highest negative Eint was ascribed to the F-C-F3∙∙∙NC-C6H2-I3 complex with a value of −1.23 kcal/mol. For Set II complexes, Eint values of F-C-X3 bearing complexes were noted within the −1.05 to −2.08 kcal/mol scope, while they ranged from −0.82 to −1.20 kcal/mol for the W-C-F3 analogs. However, Vs,max quantities exhibited higher values in the case of W-C-F3 molecules compared with F-C-X3; preferable negative Eint were ascribed to the F-C-X3 bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X3 substituents. Dispersion forces (Edisp) were identified as the dominant forces for these interactions. The obtained results provide a foundation for fields such as crystal engineering and supramolecular chemistry studies that focus on understanding the characteristics of carbon-bearing complexes.


Introduction
Noncovalent interactions are evoking resurgent interest owing to their ubiquitous contributions to several fields, including crystal materials [1,2], molecular recognition [3,4], chemical reactions [5,6], adsorption [7], and biological processes [8]. Accordingly, further understanding of the origin and nature of noncovalent interactions along with their impacts on controlling molecular systems is one of the metrics of progress in modern chemistry. σ-Hole interaction is a crucial point of concern in the scope of noncovalent interactions due to its significant roles in ligand-acceptor interactions [9,10], self-assembly [11], and anion recognition [12].
Among such σ-hole-based interactions, tetrel bonding interactions have gathered immense attention from experimental [10,38] and theoretical [23,39,40] viewpoints. Tetrel bonding plays significant roles in catalysis [41,42], supramolecular chemistry [43,44], and biological processes [6]. Preliminary studies uncovered the inability of the tetrel-bearing molecules to interact with Lewis bases (LB), NH 3 as an example, and form tetrel bonds [45,46]. Remarkably, the electrostatic potentiality of tetrel-bearing systems to participate in tetrel bonding interactions was investigated with the help of point-of-charge (PoC) [47], and these observations were then confirmed using real Lewis bases [48,49]. An up-to-date work addressed the occurrence of σ-hole interactions within tetrel-bearing molecule···Lewis acid (LA) dimers [50]. In addition, Lewis base···tetrel-bearing molecule···Lewis base trimers were precisely characterized [51]. Moreover, the favorable ability of tetrel-bearing molecules to engage in like···like and unlike interactions with other neutral [22,52] and anion [53] candidates was revealed. Further, the effect of tetrel atomic size and its substituents on the tetrel bonding interactions within W-T-X 3 ···LB complexes (where T and X/W were tetrels and halogens, respectively) were studied [47,50]. It was reported that the interaction energy became more favorable with increasing: (i) the tetrel atomic size (i.e., C < Si < Ge < Sn), (ii) electronegativity of W atom, and (iii) the atomic size of the X 3 halogens. More recently, the impact of external electric field (EEF) on these interactions was precisely assessed [54]. The negatively-directed EEF was found to decrease the interaction energies unfavorably. In contrast, the positively-directed EEF showed preferential enhancement of these energies.
Indeed, tetrel bonding interactions are still an area of active research. In view of this, the presented study was designed to develop a comprehensive understanding of the effects of Lewis basicity and acidity on the interactions in carbon-bearing complexes ( Figure 1). To pursue the aim of the current study, two sets of carbon-bearing complexes were investigated. In Set I complexes, the effect of Lewis basicity was thoroughly studied in F-C-F 3 ···NC-C 6 H 2 -X 3 /NCX (where X = F, Cl, Br, and I). In Set II complexes, the W-C-F 3 and F-C-X 3 (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centres to interact with NC-C 6 H 2 -F 3 /NCF as Lewis bases (LB). Geometrical optimization, electrostatic potential (EP) analyses, and point-of-charge (PoC) calculations were carried out for NC-C 6 H 2 -X 3 , NCX, W-C-F 3 , and F-C-X 3 molecules. Interaction energy, quantum theory of atoms in molecules (QTAIM), and noncovalent interaction (NCI) index calculations were performed to uncover the strength and nature of the considered interactions. Symmetry-adapted perturbation theory (SAPT) analysis was also utilized to investigate the dominant forces within the studied interactions of the modeled complexes. The obtained findings would be informative for various ongoing works relevant to the scope of crystal engineering and materials science.

Electrostatic Potential (EP) Analysis
EP analysis was applied as an informative tool that gives qualitative and quantitative insights into the nucleophilic and electrophilic nature of the chemical systems [55,56]. Figure 2 involves molecular electrostatic potential (MEP) maps for all the investigated systems along with the values of the Vs,min (on NC-C6H2-X3 and NCX Lewis bases), and Vs,max (on W-C-F3 and F-C-X3 Lewis acids).
From MEP maps shown in Figure 2, observable red (i.e., negative EP) regions were denoted over the N atom surfaces of the inspected LBs, spotting the favorable potentiality of the explored molecules to interact with LAs attractively. In addition, the Vs,min values of the N atom (i.e., Lewis basicity) in the NC-C6H2-X3 and NCX molecules were found to

Electrostatic Potential (EP) Analysis
EP analysis was applied as an informative tool that gives qualitative and quantitative insights into the nucleophilic and electrophilic nature of the chemical systems [55,56]. Figure 2 involves molecular electrostatic potential (MEP) maps for all the investigated systems along with the values of the V s,min (on NC-C 6 H 2 -X 3 and NCX Lewis bases), and V s,max (on W-C-F 3 and F-C-X 3 Lewis acids). decrease with decreasing the atomic size of the X3/X halogen(s) in the order of X = I > Br Cl > F. For example, Vs,min exhibited values of −36.4, −35.2, −34.2, and −31.9 kcal/mol for th N atom of the NCI, NCBr, NCCl, and NCF molecules, respectively. It is also worth men tioning that the investigated NC-C6H2-X3 molecules demonstrated more negative Vs,m values than NCX analogs; for example, the Vs,min values were −36.9 and −36.4 kcal/mol fo NC-C6H2-I3 and NCI, respectively. Passing to the inspected LA centres, notable positive EP regions (i.e., σ-hole) wit different sizes were perceived ( Figure 2). Evidently, σ-holes with more prominent size were observed within W-C-F3 molecules compared with the F-C-X3 counterparts, outlin ing the further ability of the former molecules to behave as carbon-bonding donors ove the later ones. For instance, the Vs,max values of the I-C-F3 and F-C-I3 molecules were 23 From MEP maps shown in Figure 2, observable red (i.e., negative EP) regions were denoted over the N atom surfaces of the inspected LBs, spotting the favorable potentiality of the explored molecules to interact with LAs attractively. In addition, the V s,min values of the N atom (i.e., Lewis basicity) in the NC-C 6 H 2 -X 3 and NCX molecules were found to decrease with decreasing the atomic size of the X 3 /X halogen(s) in the order of X = I > Br > Cl > F. For example, V s,min exhibited values of −36.4, −35.2, −34.2, and −31.9 kcal/mol for the N atom of the NCI, NCBr, NCCl, and NCF molecules, respectively. It is also worth mentioning that the investigated NC-C 6 H 2 -X 3 molecules demonstrated more negative V s,min values than NCX analogs; for example, the V s,min values were −36.9 and −36.4 kcal/mol for NC-C 6 H 2 -I 3 and NCI, respectively.
Passing to the inspected LA centres, notable positive EP regions (i.e., σ-hole) with different sizes were perceived ( Figure 2). Evidently, σ-holes with more prominent sizes were observed within W-C-F 3 molecules compared with the F-C-X 3 counterparts, outlining the further ability of the former molecules to behave as carbon-bonding donors over the later ones. For instance, the V s,max values of the I-C-F 3 and F-C-I 3 molecules were 23.3 and 14.2 kcal/mol, respectively. As evident, the σ-hole size increased with raising the electron-withdrawing power of the W/X 3 halogen atom(s) that supported with appreciable V s,max values in the case of fluorine-bearing molecules. Illustratively, V s,max values were 23.3, 25.5, 25.9, and 30.6 kcal/mol for W-C-F 3 molecules, as W = I, Br, Cl, and F, respectively.
Molecular Energies (i.e., E destabilization and E stabilization, in kcal/mol) As shown in Figure 3, energetic destabilization and stabilization were observed to decrease along with increasing the Lewis base···PoC intermolecular distance under the effect of negative and positive PoCs, respectively. Meanwhile, molecular stabilization energies were detected for all Lewis acid centres in the presence of negative and positive PoCs (Figure 3c,d). Generally, E stabilization enlarged along with decreasing the Lewis acid···PoC distance under the effect of negative and positive PoCs.
From Table 1, for all the NC-C 6 H 2 -X 3 ··· and NCX···PoC systems, E destabilization was found to increase as the V s,min values increase under the effect of negative PoC. For instance, E destabilization of NCF···, NCCl···, NCBr···, and NCI··· -PoC systems were 7.13, 7.62, 7.85, and 8.15 kcal/mol along with V s,min values of −31.9, −34.2, −35.2, and −36.4 kcal/mol for NCF···, NCCl···, NCBr···, and NCI··· -PoC systems, respectively. Contrarily, under the effect of positive PoC, an inverse correlation was stated between the E destabilization and the electronwithdrawing power of X 3 and X halogen atom(s) of the NC-C 6 H 2 -X 3 and NCX molecules, respectively. For instance, molecular stabilization energies (E stabilization ) were −13.06, −13.39, −13.64, and −13.92 kcal/mol for NC-C 6 H 2 -F 3 ···, NC-C 6 H 2 -Cl 3 ···, NC-C 6 H 2 -Br 3 ···, and NC-C 6 H 2 -I 3 ··· + PoC systems, respectively. Moreover, the NC-C 6 H 2 -X 3 molecules were characterized by more favorable E stabilization compared with the NCX ones that comply with V s,min values. As an example, E stabilization was −13.92 and −13.51 kcal/mol for NC-C 6 H 2 -I 3 ··· and NCI··· + PoC systems, accompanied by V s,min values of −35.7 and −31.9 kcal/mol for NC-C 6 H 2 -F 3 and NCF molecules, respectively. Turning to the W-C-F 3 ··· and F-C-X 3 ···PoC systems, the E stabilization was observed to decrease in the order F-C- PoC findings highlighted the further ability of the F-C-X 3 molecules to engage in tetrel bonding interactions compared with the W-C-F 3 ones, which verified a reversed pattern with V s,max values.

Interaction Energy
Set I and II complexes were utilized to study the effects of Lewis basicity and acidity on σ-hole interactions, respectively (see Figure 1). First, geometrical optimization for the investigated complexes was performed at MP2/aug-cc-pVTZ(PP) level of theory. The optimized structures of NC-C 6 H 2 -X 3 containing complexes, along with their intermolecular distances, are displayed in Figure 4. As well, the NCX-containing complexes are given in Figure S1. Interaction energies (E int ) were evaluated for Set I and II complexes at the same level of theory and are summerized in Table 2.      a E int was computed from the potential energy surface (PES) scan depicted in Figure S2.
As shown in Table 2a, a progressive interaction energy pattern was noticed for the investigated Set I complexes along with increasing the atomic size of the X 3 /X halogen(s), as follows X = F < Cl < Br < I. This observation undoubtedly confirmed the contributions of the nucleophilic character of the Lewis bases (i.e., the effect of Lewis basicity) on σ-hole interactions within carbon-bearing complexes. For instance, the E int were −1.16, −1.13, −1.13, and −1.05 kcal/mol for F-C-F 3 ···NCI, ···NCBr, ···NCCl, and ···NCF complexes along with V s,min values of −36.4, −35.2, −34.2, and −31.9 kcal/mol for the NCI, NCBr, NCCl, and NCF molecules, respectively.
Moreover, for Set I complexes, vast E int were clearly seen in the case of F-C-F 3 ···NC-C 6 H 2 -X 3 complexes, i.e., more than in their F-C-F 3 ···NCX counterparts, which is in line with V s,min claims that showed higher negative EP regions for the former Lewis bases. For instance, E int were −1.21 and −1.13 kcal/mol for the F-C-F 3 ···NC-C 6 H 2 -Br 3 and ···NCBr complexes alongside V s,min values of −36.5 and −5.2 kcal/mol for NC-C 6 H 2 -Br 3 and NCBr Lewis bases, respectively.
Interestingly, all Set II complexes showed negative E int with different magnitudes, outlining the prominent impact of the Lewis acidity on the strength of carbon-bearing complexes. For Set II complexes, E int of the W-C-F 3 ···Lewis base complexes were observed with lower negative values compared with the F-C-X 3 ···Lewis base analogs, in contrast with the results of the maximum positive EP regions (i.e., σ-hole). For example, from Table 2ii and Figure 2, E int were −0.82 and −1.46 kcal/mol for the I-C-F 3 ··· and F-C-I 3 ···NCF complexes and accompanied by 23.3 and 14.2 kcal/mol V s,max values for I-C-F 3 and F-C-I 3 molecules, respectively. This result was in agreement with the resurgent contributions of the X 3 substituents (i.e., X 3 = F 3 < Cl 3 < Br 3 < I 3 ) to the strength of the explored carbonbearing complexes [50].

Quantum Theory of Atoms in Molecules (QTAIM) Analysis
QTAIM analysis was performed to elucidate the origin of the intermolecular interaction [62]. QTAIM diagrams of the F-C-F 3 ···NC-C 6 H 2 -X 3 and W-C-F 3 /F-C-X 3 ···NC-C 6 H 2 -F 3 complexes are displayed in Figure 5. The corresponding diagrams for F-C-F 3 ···NCX and W-C-F 3 /F-C-X 3 ···NCF complexes are represented in Figure S3. The computed ρ b , ∇ 2 ρ b , and H b values are listed in Table 3.   Figure S2.    Figure S2.
From QTAIM diagrams demonstrated in Figure 5, three BPs and BCPs were denoted within the Set I and II complexes, highlighting the eminent contributions of the three coplanar halogens within the considered interactions that were in great agreement with previous studies [63]. The same observations were found for the F-C-F 3 ···NCX and W-C-F 3 /F-C-X 3 ···NCF complexes ( Figure S3). As listed in Table 3, positive values of ∇ 2 ρ b and H b accompanied by low values of ρ b were obtained for all the studied complexes, asserting the closed-shell nature of the deemed interactions. For both the Set I and II complexes, the topological properties were remarked to be consistent with the interaction energy pattern.
Generally, for Set II complexes, the F-C-X 3 ···Lewis base complexes were characterized by higher ρ b , ∇ 2 ρ b , and H b values over the W-C-F 3 ···Lewis base counterparts, which coincided with the corresponding MP2 energetic features ( Table 2). For example, H b of I-C-F 3 ··· and F-C-I 3 ···NCF complexes were 0.000981 and 0.001017 au, along with E int of −0.82 and −1.46 kcal/mol, respectively.

Noncovalent Interaction (NCI) Analysis
Following the announcement of Johnson et al. of the NCI index, the occurrence of inter-and intra-molecular interactions could be three-dimensionally recognized [64]. Subsequently, 2D and 3D NCI plots were generated with a 0.50 au reduced density gradient value. The color scale was in the range starting from blue (−0.035) to red (0.020) au. 3D NCI plots of F-C-F 3 ···NC-C 6 H 2 -X 3 and W-C-F 3 /F-C-X 3 ···NC-C 6 H 2 -F 3 complexes along with the F-C-F 3 ···NCX and W-C-F 3 /F-C-X 3 ···NCF analogs are illustrated in Figure 6 and Figure S4, respectively. Similarly, for the same pattern of complexes, 2D NCI-RDG plots were generated and are depicted in Figures S5 and S6.
As shown in Figure 6, the green surfaces between the interacting species outlined the weak attractive interactions within the Set I and II complexes. Further, the strength enhancement of the studied complexes was obviously noted by increasing the size of the obtained green regions ( Figure 6 and Figure S4). Notably, the prominent role of the coplanar halogens was observed, ensuring the QTAIM findings. As can be seen from Figures S5 and  S6, all the spikes were found with negative values of sign(λ 2 )ρ, affirming the occurrence of weak attractive interactions between the two interacting species.

Symmetry-Adapted Perturbation Theory (SAPT) Calculations
SAPT analysis was previously applied for its efficiency in analyzing the physical energetic components of noncovalent interactions [65]. Figure 7 represents the attractive forces versus the repulsive ones that were obtained from Total SAPT2+(3)dMP2 energies, revealing the most dominant energetic aspect within the interactions of Set I and II complexes. Table S1 lists the corresponding energetic values of such attractive and repulsive forces.

Symmetry-Adapted Perturbation Theory (SAPT) Calculations
SAPT analysis was previously applied for its efficiency in analyzing the physical energetic components of noncovalent interactions [65]. Figure 7 represents the attractive forces versus the repulsive ones that were obtained from Total SAPT2+(3)dMP2 energies, revealing the most dominant energetic aspect within the interactions of Set I and II complexes. Table S1 lists the corresponding energetic values of such attractive and repulsive forces.
As can be seen from Figure 7, negative energetic values were denoted for the electrostatic (Eelst), induction (Eind), and dispersion energy (Edisp) forces, outlining their contributions in stabilizing all the Set I and II complexes. Apparently, the Edisp was the most dominant force within such attractive forces. On the other hand, unfavorable contributions for the exchange energy (Eexch) with positive values were also admitted. Illustratively, Eelst, Eind, Edisp, and Eexch values were −2.66, −0.78, −5.24, and 7.53 kcal/mol for F-C-I3•••NC-C6H2-F3 complex (Table S1).
With respect to Set I complexes, the total attractive forces also affirmed the favorability of F-C-F3•••NC-C6H2-X3 complexes, with highly energetic features, over the F-C-F3•••NCX analogs. For Set II complexes, significant total attractive forces in the case of the F-C-X3 bearing complexes compared to W-C-F3 bearing complexes, which might be interpreted as a result of the resurgent contributions of X3 substituents. Generally, the total attractive forces (i.e., Eelst, Eind, and Edisp) were found to be consistent with the energetic features with some exceptions. Such exceptions might be interpreted by considering the Eexch contributions. Illustratively, the Eelst/Eind/Edisp/Eexch values of the F-C-F3•••NCF and F-

Methods and Materials
In the current study, Set I and II complexes were used to investigating the effects of Lewis basicity and acidity on σ-hole interactions, respectively (see Figure 1). In that spirit, the F-C-F3•••NC-C6H2-X3/NCX and W-C-F3/F-C-X3•••NC-C6H2-F3/NCF complexes (where X and W = F, Cl, Br, and I) were well-characterized using various ab initio calculations. Geometrical optimization was first carried out for the investigated monomers at the MP2/aug-cc-pVTZ level of theory [66][67][68] for all atoms, except Br and I atoms. The aug-cc-pVTZ-PP basis set was utilized for the excepted atoms [66,67]. To envisage the electrophilic and nucleophilic regions over the molecular surfaces of the optimized mole- As can be seen from Figure 7, negative energetic values were denoted for the electrostatic (E elst ), induction (E ind ), and dispersion energy (E disp ) forces, outlining their contri-butions in stabilizing all the Set I and II complexes. Apparently, the E disp was the most dominant force within such attractive forces. On the other hand, unfavorable contributions for the exchange energy (E exch ) with positive values were also admitted. Illustratively, E elst , E ind , E disp, and E exch values were −2.66, −0.78, −5.24, and 7.53 kcal/mol for F-C-I 3 ···NC-C 6 H 2 -F 3 complex (Table S1).
With respect to Set I complexes, the total attractive forces also affirmed the favorability of F-C-F 3 ···NC-C 6 H 2 -X 3 complexes, with highly energetic features, over the F-C-F 3 ···NCX analogs. For Set II complexes, significant total attractive forces in the case of the F-C-X 3 bearing complexes compared to W-C-F 3 bearing complexes, which might be interpreted as a result of the resurgent contributions of X 3 substituents. Generally, the total attractive forces (i.e., E elst , E ind , and E disp ) were found to be consistent with the energetic features with some exceptions. Such exceptions might be interpreted by considering the E exch contributions. Illustratively, the E elst /E ind /E disp /E exch values of the F-C-F 3 ···NCF and F-C-Cl 3 ···NCF complexes were −1.26/−0.03/−1.73/1.91 and −1.09/−0.20/−3.00/3.32 kcal/mol, respectively.

Methods and Materials
In the current study, Set I and II complexes were used to investigating the effects of Lewis basicity and acidity on σ-hole interactions, respectively (see Figure 1). In that spirit, the F-C-F 3 ···NC-C 6 H 2 -X 3 /NCX and W-C-F 3 /F-C-X 3 ···NC-C 6 H 2 -F 3 /NCF complexes (where X and W = F, Cl, Br, and I) were well-characterized using various ab initio calculations. Geometrical optimization was first carried out for the investigated monomers at the MP2/aug-cc-pVTZ level of theory [66][67][68] for all atoms, except Br and I atoms. The aug-cc-pVTZ-PP basis set was utilized for the excepted atoms [66,67]. To envisage the electrophilic and nucleophilic regions over the molecular surfaces of the optimized molecules, the electrostatic potential (EP) analysis was carried out. In this perspective, molecular electrostatic potential (MEP) maps were built and then generated using 0.002 electron density envelopes according to the literature [69]. Further quantitative assessment was established by the evaluation of the surface electrostatic potential extrema in terms of V s,min and V s,max values, with the help of the Multiwfn 3.7 software [70], along the molecular surface of the inspected LB and LA, respectively.
The PoC approach was utilized to investigate the Lewis basicity and acidity roles on the tetrel-based interactions from an electrostatic perspective [18,47,50,71]. Using PoC approach, the effect of N··· and C···PoC distances were examined for the considered the NC-C 6 H 2 -X 3 /NCX (LB)··· and W-C-F 3 ···/F-C-X 3 (LA)···PoC systems under the effect of PoC = ±0.50 au in distance range of 2.5-5.5 Å along the x-axis with a 0.1 Å step size. The molecular stabilization energies (E stabilization ) were then evaluated and given from Equation (1) [63,72,73]: In order to thoroughly investigate the effect of Lewis basicity on interactions concerned with the carbon-bearing complexes, the NC-C 6 H 2 -X 3 and NCX models were devoted to interacting with F-C-F 3 . Alternatively, the W-C-F 3 and F-C-X 3 molecules were adopted for interactions with NC-C 6 H 2 -F 3 and NCF to outline the effect of Lewis acidity on tetrel bonding interactions. Geometrical optimization was performed for the designed Set I and II complexes. Using the optimized complexes, the interaction energies were evaluated using Equation (2). Principally, the Boys-Bernardi procedure was utilized to give a proper correction for the resulted interaction energies from the basis set superposition error (BSSE) [74].
E int = E Set I and Set II complexes − E LA in complex + E LB in complex + E BSSE (2) where E Set−I and Set−II complexes , E LA in complex , and E LB in complex represent energies of the complex, the deformed structures of LA, and LB, respectively. Energies of deformed monomers were considered based on their respective coordinates in the optimized Set I and II complexes.
To give qualitative and quantitative descriptions of the nature of the intermolecular interactions, quantum theory of atoms in molecules (QTAIM) [75] and noncovalent interaction (NCI) [64] analyses were carried out via Multiwfn 3.7 package [70]. The QTAIM diagrams and 2D/3D NCI plots were generated with the help of Visual Molecular Dynamics (VMD) software [76]. Gaussian 09 software was utilized for performing the executed calculations [77].

Conclusions
Ab initio calculations were performed to investigate the effects of Lewis basicity and acidity on the tetrel bonding interactions using F-C-F 3 ···NC-C 6 H 2 -X 3 /NCX and W-C-F 3 /F-C-X 3 ···NC-C 6 H 2 -F 3 /NCF complexes (i.e., Set I and II complexes), respectively. Regarding the Lewis basicity effect, the MP2 energetic quantities of Set I complexes further confirmed the favorability of the F-C-F 3 ···NC-C 6 H 2 -X 3 complexes with favorable E int (i.e., more negative) over their F-C-F 3 ···NCX counterparts. Additionally, E int of Set I complexes increased along with decreasing the electron-withdrawing power of the X 3 /X halogen(s) in the following order F < Cl < Br < I. Regarding the Lewis acidity effects, V s,max quantities exhibited higher values in the case of W-C-F 3 molecules compared with F-C-X 3 . Nevertheless, higher negative E int were ascribed to the F-C-X 3 bearing complexes compared with the W-C-F 3 bearing ones. QTAIM diagrams and NCI plots validated the prominent contributions of the X 3 halogen substituents. Moreover, SAPT observations identified E disp as the most dominant energetic aspect that contributed to the total strength of all the studied complexes. These observations provide informative characteristics of carbon-bearing complexes that may be fundamental in future studies related to crystal engineering and materials science.