Single-Crystal X-ray Diffraction Analysis of Inclusion Complexes of Triflate-Functionalized Pillar[5]arenes with 1,4-Dibromobutane and n-Hexane Guests

Abstract

Herein, we report the single-crystal X-ray diffraction analysis of supramolecular host–guest systems based on triflate-functionalized pillar[5]arenes and 1,4-dibromobutane or n-hexane. The guest molecule was stabilized inside the pillar[5]arene cavity by C–H⋯π and C–H⋯O interactions. These inclusion complexes were further self-assembled into supramolecular networks by various non-bonding interactions such as C-H⋯O, C-H⋯F, Br⋯Br, F⋯F, etc. The intermolecular interactions present in these systems were investigated in detail. One of the supramolecular systems analyzed in this study exhibited intermolecular F⋯F interactions which were operative between the adjacent pillararene rims. It was observed that the type of guest molecule considerably influenced the mutual interactions of pillararene macrocycles and their networking pattern in the crystal. The inclusion complexes were further studied by Hirshfeld surface analysis which not only provided a visual representation of the intermolecular interactions experienced by the systems but gave a quantitative account of these various interactions.

1. Introduction

Pillararene-based macrocycles are gaining considerable importance in contemporary research due to their peculiar structural properties and π-rich deep cavities which enable them to encapsulate a variety of small guest species [1,2,3,4,5]. Pillararene systems containing substituted halogen atoms in their outer rims are of especial interest in the field of supramolecular chemistry because these types of halogen-containing macrocycles can self-assemble into a supramolecular network by halogen–halogen and/or halogen–hydrogen interactions. Supramolecular host–guest systems constructed by such halogen-based non-covalent interactions have drawn considerable interest in recent years [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. Heaver halogens, particularly bromo and iodo derivatives, have been widely utilized in the assembly of such systems because they exhibit electrophilic characteristics and can interact with electron-pair-donating heteroatoms (O, N, S) or anions because of the anisotropic distribution of the electrostatic potential around the atomic center. However, supramolecular systems mediated by F⋯F interactions are not commonly encountered [20,21], especially for macrocyclic systems such as pillararenes.

Pillar[n]arenes possess excellent guest encapsulation and molecular recognition properties, making them ideal building blocks for the preparation of supramolecular polymers [6,7]. A novel supramolecular linear polymer system based on the guest encapsulation of 1,4-dibromobutane by permethylated-pillar[5]arenes both in solution and in a solid state has been reported previously [6,7]. The crystal structure of the obtained inclusion complex shows that the guest molecule is tightly stabilized inside the pillar[5]arene cavity by C–H⋯π and C–H⋯O interactions. The novel linear supramolecular assembly is formed by the bonding between the bromine atoms of encapsulated dibromobutane molecules located inside the pillar[5]arene cavity with the adjacent inclusion complex, through Br⋯Br interactions.

In this work, we report the co-crystal structures of pillararene systems conjugated with mono- and di-substituted triflate moieties with dibromobutane and n-hexane guests. The detailed comparison study provides insight on the effect of halogen-containing guest molecules on the supramolecular behavior of these inclusion systems. The structural features and supramolecular host–guest interactions of these co-crystalline systems (Pil_TF1_ButBr2, Pil_TF1_Hex, Pil_TF2_ButBr2 and Pil_TF2_Hex) are addressed and discussed.

2. Materials and Methods

The single-crystal data collection was made either using the Bruker X8 prospector (Germany) diffractometer with Cu-Kα radiation or the Rigaku Rapid II (Japan) diffractometer with Mo-Kα radiation. In the former case, the reflection frames were integrated with the Bruker SAINT Software package using a narrow-frame algorithm. Finally, the structure was solved using the Bruker SHELXTL software package and refined using SHELXL-2017/1. The data collected using the Rigaku diffractometer were processed using the ‘Crystalclear’ software package. The structure was then solved by direct methods using the CrystalStructure crystallographic software package and the refinement was performed using SHELXL-2017/1. Nuclear magnetic resonance (NMR) spectroscopy was conducted using the Bruker DPX Avance 400 MHz (Germany) spectrometer. Electron impact ionization (EI) mass spectrometry was performed using the Thermo Scientific DFS High Resolution GC/MS (Germany) mass spectrometer. 1-(1,4-ditriflate)-2,3,4,5-dimethoxy pillar[5]arene (Pil-TF2) was synthesized based on the previously reported procedure [22].

2.1. Synthesis of 1-(1-Triflate-4-Methoxy)-2,3,4,5-Dimethoxy Pillar[5]arene (Pil-TF1)

To a solution of 1-(1-hydroxy-4-methoxy)-2,3,4,5-dimethoxy pillar[5]arene [23] (147 mg, 0.2 mmol) in CH₂Cl₂ (30 mL), pyridine (18 μL, 0.22 mmol) was added and the mixture was stirred at 0 °C for 10 min. Triflic anhydride (34 μL, 0.2 mmol) was then added at 0 °C, and the mixture was stirred at room temperature for 4 h. The solution was washed with aqueous HCl solution (1.0 M, 3 × 30 mL), solvent was removed under reduced pressure and the residue was purified using column chromatography to afford the desired product Pil-TF1 as a white solid (Yield 121 mg, 70%). ¹H NMR (400 MHz, CDCl₃), δ: 3.69 (m, 27H), 3.80 (m, 8H), 3.87 (s, 2H), 6.75 (m, 2H), 6.80 (m, 6H), 6.87 (s, 1H), 7.15 (s, 1H). ¹³C NMR (100 MHz, CDCl₃), δ: 29.5, 29.6, 29.6, 30.7, 52.4, 55.5, 55.6, 55.6, 55.8, 55.9, 55.9, 56.0, 113.6, 113.7, 113.7, 114.0, 114.0, 114.1, 114.1, 114.2, 123.1, 126.0, 127.0, 128.3, 128.5, 128.5, 128.9, 129.3, 130.0, 132.5, 141.1, 150.6, 150.8, 150.9, 150.9, 151.0, 156.1. HRMS: (m/z): calculated for [M]⁺: 868.2740 (for C₄₅H₄₇O₁₂F₃S); found 868.2737.

2.2. Preparation of Single Crystals for X-ray Diffraction

Suitable single crystals of the inclusion complexes Pil-TF2_ButBr2, Pil-TF2_Hex, Pil-TF1_ButBr2 and Pil-TF1_Hex were grown using the slow solvent evaporation method from dichloromethane/1,4 dibromobutane (1 mL, 90: 10; v/v) or dichloromethane/n-hexane mixtures. All non-hydrogen atoms were refined anisotropically and hydrogen atoms were refined using the riding model. The crystallographic data for structures reported in this paper have been deposited at the Cambridge Crystallographic Data Centre (CCDC 2244581-2244584).

3. Results and Discussion

3.1. Crystal Structures of Triflate-Functionalized Pillar[5]arenes with 1,4-dibromobutane or n-hexane

The crystal structures of di-substituted triflate pillar[5]arene obtained from the solution containing 1,4-dibromobutane (Pil_TF2_ButBr2) and those obtained from the solution containing n-hexane (Pil_TF2_Hex) are depicted in Figure 1 and their crystallographic features are given in

Table 1. Summary on the nature and various crystallographic parameters of Pil_TF2_ButBr2 and Pil_TF2_Hex.

Crystal Sample	Pil-F2-ButBr2	Pil-TF2-Hexane
Chemical formula	C49H52Br2F6O14S2	C51H58F6O14S2
Mr	1202.84	1073.09
Crystal system, space group	Mono-clinic, P21/c	Mono-clinic, P21/c
Temperature (K)	150	150
a, b, c (Å)	18.4426 (10), 18.580 (1), 15.8047 (7)	18.1057 (13), 18.7444 (14), 15.8021 (11)
α, β, γ (°)	98.962 (7)	99.305 (4)
V (Å3)	5349.6 (5)	5292.4 (7)
Z	4	4
Radiation type	Mo Kα	Cu Kα
µ (mm−1)	1.68	1.65
Crystal size (mm)	0.20 × 0.20 × 0.16	0.21 × 0.18 × 0.17
Diffractometer	Rigaku R-AXIS RAPID	Bruker APEX-II CCD
Absorption correction	Multi-scan ABSCOR (Rigaku, 1995)	Multi-scan SADABS2016/2—Bruker AXS area detector scaling and absorption correction
Tmin, Tmax	0.72, 0.79	0.71, 0.78
No. of measured, independent and observed [I > 2σ(I)] reflections	37,489, 9339, 5489	40,804, 8995, 4711
Rint	0.049	0.098
(sin θ/λ)max (Å−1)	0.595	0.595
R[F2 > 2σ(F2)], wR(F2), S	0.095, 0.321, 1.04	0.099, 0.348, 1.04
No. of reflections	9339	8995
No. of parameters	741	676
No. of restraints	287	89
H-atom treatment	Constrained	Constrained
Δρmax, Δρmin (e Å−3)	1.40, −0.65	0.74, −0.63

. As expected, both Pil_TF2_ButBr2 and Pil_TF2_Hex crystals constitute pillar[5]arene macrocycle encapsulated with either dibromobutane or n-hexane in its cavity. The dibromobutane present in the cavity of Pil_TF2 exhibits positional disorder and hence the crystal refinement could be made possible by assigning its location at two different sites in the cavity. In Figure 1, the position of those dibromobutanes with higher occupancy (60%) has been shown. Furthermore, one of the triflate sites in this crystal exhibited positional disorder with respect to the corresponding sulfur and two attached oxygen atoms, and this too is refined over two sites with 70% and 30% occupancies, respectively. Moreover, in the case of Pil_TF2_Hex, one of the triflate sites exhibited positional disorder with respect to the corresponding sulfur atom and thus performed refinement over two sites (with around 63% and 37% occupancies, respectively).

The crystal structure of mono-substituted triflate pillar[5]arene obtained from the solution containing 1,4 dibromobutane (Pil_TF1_ButBr2) and those obtained from the solution containing n-hexane (Pil_TF2_Hex) are shown in Figure 2. The crystallographic parameters of both these crystals are provided in

Table 2. Summary on the nature and various crystallographic parameters of Pil_TF1_ButBr2 and Pil_TF1_Hex.

Crystal Sample	Pil-F1-ButBr2	Pil-TF1-Hexane
Chemical formula	C49H55Br2F3O12S	C51H61F3O12S
Mr	1084.81	955.05
Crystal system, space group	Orthorhombic, Pna21	Orthorhombic, Pna21
Temperature (K)	150	150
a, b, c (Å)	36.345 (4), 12.1749 (13), 11.4616 (13)	36.5154 (14), 12.1508 (5), 11.4520 (4)
V (Å3)	5071.7 (10)	5081.2 (3)
Z	4	4
Radiation type	Cu Kα	Cu Kα
µ (mm−1)	3.01	1.16
Crystal size (mm)	0.22 × 0.21 × 0.18	0.21 × 0.17 × 0.12
Diffractometer	Bruker APEX-II CCD	Bruker APEX-II CCD
Absorption correction	Multi-scan SADABS2016/2—Bruker AXS area detector scaling and absorption correction	Multi-scan SADABS2016/2—Bruker AXS area detector scaling and absorption correction
Tmin, Tmax	0.57, 0.63	0.79, 0.84
No. of measured, independent and observed [I > 2σ(I)] reflections	28,160, 7434, 6869	32,409, 7710, 7322
Rint	0.057	0.038
(sin θ/λ)max (Å−1)	0.596	0.595
R[F2 > 2σ(F2)], wR(F2), S	0.116, 0.329, 1.51	0.073, 0.216, 1.00
No. of reflections	7434	7710
No. of parameters	660	615
No. of restraints	244	127
H-atom treatment	Constrained	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.74, −1.27	0.99, −0.69

. As in the case of its ditriflate analogue, both Pil_TF1_ButBr2 and Pil_TF1_Hex crystals comprise pillar[5]arene macrocycles along with either dibromobutane or n-hexane guests in the cavity. The dibromobutane present in the cavity of Pil_TF1 too exhibits positional disorder as in the case of Pil_TF1_ButBr2 and hence refined over two different sites in the pillararene cavity with 53% and 47% occupancies, respectively. Pil_TF2_Hex also exhibited positional disorder at one of sulfur atoms belonging to the triflate site with around 57% and 43% occupancies, respectively.

3.2. Host–Guest Inclusion Complexes of Di- and Mono-Substituted Triflate Pillar[5]arenes with 1,4-dibromobutane and n-hexane

The crystal structures of all the four pillararene systems show that 1,4-dibromobutane/n-hexane guest species are threaded inside the pillararene cavity forming 1:1 inclusion complex. It can be seen that almost all H- atoms of the guest molecules are capable of involving bonding with a pillararene ring either via C-H⋯O or C-H⋯π non-bonding interactions. The nature of these various non-bonding interactions is depicted in Figure 3 and Figure 4 and their quantitative details are provided in the Supporting Information.

3.3. Intermolecular Non-Bonding Interactions among Pil_TF2 Crystals

The 1:1 inclusion complexes of triflate-substituted pillar[5]arenes and dibromobutane/n-hexane are capable of involving many non-bonding interactions in their crystal network. The non-bonding interactions (less than the van del Waals range) experienced by Pil_TF2_ButBr2 and Pil_TF2_Hex from their immediate neighbors are shown in Figure 5. In the case of Pil_TF2_Hex crystals, it can be seen that the intermolecular non-bonding interactions included C-H⋯F and C-H⋯O types. However, in the case of Pil_TF2_ButBr2 crystals, the range of these non-bonding interactions extends further to very interesting and highly significant F⋯F and Br⋯Br interactions in addition to C-H⋯F and C-H⋯O bonds (Figure 5).

The quantitative details of all these non-bonding interactions are provided in

Table 3. Intermolecular non-bonding interactions (shorter than the sum of van der Walls radii) in the Pil_TF2_ButBr2 crystals (Å, °).

A-B⋯C	A-B	B⋯C	A⋯C	A-B⋯C
C36-F2⋯F5 i	1.31(1)	2.753(8)	3.61(1)	121.06(6)
C37-F5⋯F2 i	1.27(1)	2.753(8)	3.88(1)	147.3(8)
C40-H40A⋯F3 ii	0.96	2.588	3.232(9)	124.6
C36-F3⋯H40A ii	1.32(1)	2.588	3.559	128.0
C34-O10⋯H35A iii	1.382(6)	2.546	3.760	144.8
C35-H35A⋯O10 iv	0.970	2.546	3.377(6)	143.7

Symmetry code: (ⁱ) −x, 1−y, 1−z; (ⁱⁱ) 1−x, 1−y, 1−z; (ⁱⁱⁱ) x, 1.5−y, −1/2+z; (^iv) x, 1.5−y, 1/2+z.

and

Table 4. Intermolecular non-bonding interactions (shorter than the sum of van der Walls radii) in the Pil_TF2_Hex crystals (Å, °).

A-B⋯C	A-B	B⋯C	A⋯C	A-B⋯C
C40-H43C⋯F4 i	0.96	2.631	3.31(1)	127.6
C37-F4⋯H43C i	1.45(1)	2.631	3.52	116.6
C35-H35B⋯O9 ii	0.97	2.563	3.381(6)	142.2
C30-O9⋯H35B iii	1.389(6)	2.563	3.770	143.4
C38-H38A⋯O11 iv	0.961	2.719	3.395(9)	128.0
S1A-O11⋯H38A v	1.41(1)	2.719	3.33	103.1

Symmetry code: (ⁱ) −x, 1−y, 1−z; (ⁱⁱ) x, 1/2−y, −1/2+z; (ⁱⁱⁱ) x, 1/2−y, 1/2+z; (^iv) 1−x, 1/2+y, 1.5−z; (^v) 1−x, −1/2+y, 1.5−z.

where both interaction distances and corresponding angles are given. Due to the positional disorder of the dibromobutane guest in the crystals, it is not possible to provide an accurate quantification of Br⋯Br interactions in the crystal and hence its values are excluded in Table 3. It is evident from Table 3 that F⋯F interaction distance in Pil_TF2_ButBr2 crystals is 2.753(8) Å, which is ca. 6% shorter than the sum of the respective van der Waals atomic radii (2.94 Å). A comprehensive work on various aspects of C-F⋯F-C and C–H⋯F–C interactions in organic crystals was reported by Levina et al. [20]. Through various experimental and theoretical calculations in their work, the authors reported that the presence of C–F⋯F–C interactions in crystals could be confirmed if F⋯F distances are less than 2.94 Å. Therefore, the F⋯F bond length of 2.753(8) Å shown by the Pil_TF2_ButBr2 crystal reveals that these pillararene molecules are held together to form a supramolecular network by a great contribution of the rare F⋯F mediated interactions.

A close observation of the Pil_TF2_ButBr2 and Pil_TF2_Hex crystals reveals that both these molecules have similar packing in the crystal. A short section of their crystal network (comprising four pillar[5]arene units) is given in Figure 6 which shows that the triflate fractions of every two adjacent pillar[5]arene molecules are close to each other in both crystals. In the case of the Pil_TF2_Hex crystals, the packing is in such a manner that the closest F⋯F distance between two adjacent pillar[5]arenes is 2.941 Å, which is almost equal to the sum of their respective van der Waals atomic radii. At the same time, in the case of Pil_TF2_ButBr2, the closest F⋯F distance, as mentioned earlier, is found to be reduced significantly to 2.753(8) Å, thereby enabling efficient F⋯F interactions in the crystal. The reason for this remarkable difference in these two crystal samples is the presence of different types of guest molecules encapsulated within them. When dibromobutane is encapsulated in the Pil_TF2 crystal, appreciable Br⋯Br interaction between two adjacent dibromobutanes occurs, which in turn causes the two triflate fragments to move close to each other, enabling F⋯F interactions. Therefore, it is clear that the nature of the guest molecule influences the supramolecular characteristics of the host molecule and proper selection of such host–guest combinations can generate interesting functional systems.

The two-dimensional packing of both Pil_TF2_Hex and Pil_TF2_ButBr2 crystals is provided in Figure 7 and Figure 8, respectively, which provided a clear demonstration of how different F⋯F, F⋯H and Br⋯Br occurred in the crystal network and the impact of these interactions on the crystal packing. In the case of Pil_TF2_Hex, the pilla[5]arene units are arranged linearly in different rows. In this linear assembly of each row, two adjacent pillar[5]arene molecules are co-facially interacted with by two F⋯H bonds, forming a dimeric unit. However, there is no significant interaction involving F⋯F, F⋯H bonds between any dimer and its adjacent counterpart in the linear assembly or between two pillar[5]arenes in different rows. In Pil_TF2_ButBr2, crystals show significant influences of F⋯F, F⋯H and Br⋯Br interactions. In addition, the pillar[5]arene units are arranged linearly as co-facial dimers in different rows by F⋯H bonds as in the case of Pil_TF2_Hex. Moreover, to these F⋯H bonds between the two adjacent pillar[5]arenes, there are Br⋯Br interactions between two dibromobutane molecules which are encapsulated by the pillar[5]arenes in the linear chain. The interesting feature of this Br⋯Br interaction is not found between the guest molecules of co-facial dimeric units in the pillar[5]arene linear assembly but between two pillar[5]arenes of adjacent dimers. The combined effect of these two types of interaction, namely F⋯H and Br⋯Br, is that all pillar[5]arene-dibromobutane host–guest systems in the Pil_TF2_ButBr2 crystal are connected to one another along the linear assembly making a chain of pillar[5]arenes in the network. Furthermore, pillararene in each linear chain is bonded to a neighboring pillararene of a different row through F⋯F interactions at two macrocyclic sites. It should be noted that alternate Pil_TF2 molecules in the linear assembly engage these F⋯F interactions towards pillararenes of the same rows and the other alternate Pil_TF2 molecules interact with the macrocycles lying on the rows on the opposite side. As a result, the pillararene self-assembly in the Pil_TF2_ButBr2 crystal could be considered as a linear propagation of a host–guest species at different rows mediated by the combined effect of F⋯H and Br⋯Br interactions, along with efficient F⋯F interactions propagating sideways with respect to this linear chain in an alternate frequency. Although both Pil_TF2_Hex and Pil_TF2_ButBr2 crystals show similar patterns in their networks, the latter crystals are much more significant from a supramolecular point of view. This difference signifies the effect of guest molecules in the supramolecular characteristics of the host–guest systems.

In Pil_TF1 crystals, the guest molecule contributes significantly to the intermolecular interactions. The 1:1 inclusion complexes of Pil_TF1 and 1,4-dibromobutane/n-hexane are capable of involving non-bonding interactions with immediate neighbors in their crystal networks, which are given in Figure 9 (which shows those that are less than the van der Waals range).

In both Pil_TF1_Hex and Pil_TF1_ButBr2 crystals, there are efficient C-H⋯F interactions. However, in the latter case, where the dibromobutane is encapsulated, the total number of such C-H⋯F interactions experienced by a single pillar[5]arene unit is doubled when compared to its hexane encapsulated counterpart as shown in Figure 9. The quantitative details of all these C-H⋯F non-bonding interactions exhibited by Pil_TF1_ButBr2 and Pil_TF1_Hex crystals are provided in the Supporting Information where both interaction distances and corresponding angles are given.

The crystal network of both Pil_TF1_Hex and Pil_TF1_ButBr2 have similar features with linear assembly of pillar[5]arene units arranged in different arrays. It is interesting to note that in the case of the Pil_TF1_Hex crystal, each pillar[5]arene in the linear chain is connected by an F⋯H bond at both ends (Figure 10). In the case too of the Pil_TF1_ ButBr2 crystal, each pillar[5]arene in the linear chain is connected by an F⋯H bond at both ends. In addition, there is a sideways interaction through another set of F⋯H bonds between pillar[5]arenes in different rows, which make it an overall two-dimensionally propagated F⋯H bond structure, as demonstrated in Figure 11.

It is interesting to note that the mono-triflate upon hexane encapsulation gives a linear chain while di-triflate upon the same guest encapsulation gives a linear assembly with co-facial dimeric units as demonstrated in the Supporting Information.

3.4. Hirshfeld Surface Analysis of Co-Crystals Constituting Triflate-Functionalized Pillar[5]arenes and 1,4-dibromobutane/n-hexane

The non-bonding interactions experienced by triflate-functionalized pillararens discussed in this study were further investigated by Hirshfeld surface analysis. The Hirshfeld surface analysis offers a visual representation of the intermolecular interactions and, thus, serves as a powerful tool for gaining additional insights into crystal structures [24,25,26]. There are two main characteristic features in the Hirshfeld surface analysis, namely, 3D dnorm surface images and 2D fingerprint plots. The 3D dnorm surface is helpful for visualizing and analyzing the intermolecular interactions experienced by a species in the crystal. The red colored regions on the Hirshfeld surface indicate the intermolecular contacts shorter than the sum of the relevant van der Waals radii. White regions indicate intermolecular distances close to van der Waals contacts and blue regions are contacts longer than the sum of the respective van der Waals radii. At the same time, the 2D fingerprint plots give a quantitative summarization of the nature and type of various intermolecular contacts experienced by a particular moiety in the crystal. In the present study, the Hirshfeld surface analysis was performed using Crystal Explorer 17.1 [27]. Due to positional disorder, the structures of these crystals were remodeled in this section for the generation of the Hirshfeld surface by choosing only the disordered components of greater occupancy. This is achieved by manually editing the CIF to remove atoms from all the disorder components except the one which is more populated and setting all the atoms to be fully occupied.

The Hirshfeld surface mapped with the dnorm function for Pil_TF2_ButBr2 clearly shows intense red spots which correspond to the F⋯F interactions (Figure 12). Other interactions such as H⋯H, F⋯H, O⋯H, C⋯H and Br⋯Br could be seen in the surface as faded red spots and white regions. The red areas arising from intermolecular F⋯F interactions are very intense implying the dominance of these interactions in the crystal. As expected, the appearance of the Hirshfeld surface of Pil_TF2_Hex is much different from that of Pil_TF2_ButBr2 due to a lack of intense F⋯F intermolecular interactions between them. Some diffused red/white regions in the surface of Pil_TF2_Hex dnorm is due to H⋯H, F⋯H, C⋯H or O⋯H interactions.

From the 2D fingerprint plots, the major intermolecular interactions in the Pil_TF2_ButBr2 crystals are H⋯H (38.7%), F⋯H (20.1), O⋯H (17.2%), C⋯H (11.4%), Br⋯H (2.2%) and F⋯F (2.4%). The 2D fingerprint plot shows that the Br⋯Br interactions in this crystal contribute 0.8% of the total intermolecular interactions, which is significant when considering the fact that only two bromine atoms are present in the asymmetric unit of the crystal. In the case of the Pil_TF2_Hex crystal, the major intermolecular interactions corresponding to the 2D fingerprint plots are H⋯H (42.4%), F⋯H (21.5), O⋯H (17.9%), C⋯H (11.5%) and F⋯F (1.5%). As expected, all these percentage contributions in the Pil_TF2_Hex crystal are higher than those values of Pil_TF2_ButBr2, except for the contribution of F⋯F interactions due to the absence Br-mediated interactions in the former crystals. Even then, the superior contribution of F⋯F interactions in Pil_TF2_ButBr2 compared to Pil_TF2_Hex is in full agreement with the observation that the encapsulation of 1,4-dibromobutane by the pillararene promoted F⋯F bonding, as demonstrated earlier.

As there is no remarkable difference in the non-bonding interactions between the crystal structures, the Hirshfeld surface mapped with the dnorm function for Pil_TF1_ButBr2 and Pil_TF1_Hex exhibited almost similar surface features, which is shown in the Supporting Information. Regarding the quantitative details, the major intermolecular interactions in the Pil_TF1_ButBr2 crystals based on the 2D fingerprint plots are H⋯H (48.5%), O⋯H (16.8%), C⋯H (14.5%), F⋯H (12.8%) and Br⋯H (4.5%). At the same time, the corresponding contributions for Pil_TF1_Hex crystals are H⋯H (52.8%), O⋯H (17.1%), C⋯H (14.5%) and F⋯H (13.4%). It should be noted that the contributions of F⋯F and Br⋯Br interactions are insignificant (0.0% and 0.1%, respectively) in the Pil_TF1_ButBr2 crystals.

4. Conclusions

To conclude, host–guest supramolecular systems based on mono- and di-triflate-functionalized-pillar[5]arene with 1,2-dibromobutane/n-have been developed. Efficient host–guest complexation between the pillararenes and 1,4-dibromobutane and n-hexane has been observed in all these systems. Both mono- and di-functionalized-pillar[5]arens were self-arranged into linear assembly in their crystal upon guest encapsulation by employing various non-bonding interactions such as F⋯H bonding. However, in one of the supramolecular systems comprising di-functionalized-pillar[5]arens with dibromobutane, highly efficient and useful F⋯F and Br⋯Br interactions were observed in the crystal network. This result suggests that these types of fluorine-functionalized pillarane, if subjected to fine tuning by the appropriate selection of guest molecules, could be employed to generate useful functional materials.