1-[1,4-Bis(but-3-en-1-yloxy)]-2,3,4,5-(1,4-dimethoxy)pillar[5]arene–1,4-dibromobutane 1:1 inclusion complex

In the title compound, both the host and guest are completed by crystallographic twofold symmetry (one carbon atom of the host lies on the rotation axis). The pentagonal-shaped macrocycle has a pair of buteneoxy substituents on one of its faces and one molecule of 1,4-dibromobutane is encapsulated within the cavity of the pillararene, forming a 1:1 inclusion complex.

In the title compound, C 51 H 58 O 10 ÁC 4 H 8 Br 2 , both the host and guest are completed by crystallographic twofold symmetry (one carbon atom of the host lies on the rotation axis). The pentagonal-shaped macrocycle has a pair of buteneoxy substituents on one of its faces and one molecule of 1,4-dibromobutane is encapsulated within the cavity of the pillararene, forming a 1:1 inclusion complex. The terminal alkene parts, which project outwards from the pillararene ring, exhibit positional disorder over two sets of sites in a 0.52 (2): 0.48 (2) ratio. The host and guest interact via C-HÁ Á ÁO, C-HÁ Á ÁBr and C-HÁ Á Á interactions and adjacent host molecules interact via C-HÁ Á ÁO and C-HÁ Á Á bonds. Pillar[n]arenes are characterized by guest encapsulation and molecular recognition properties, which are due to their pillar-shaped structures, nano-sized cavities and availability of multiple rim sites for substitutions, and which makes them useful functional materials for several applications in materials chemistry, nanotechnology and biomimmetic systems (Ogoshi et al., 2016;Li et al., 2020). Appropriate derivatization of pillararene macrocycles can be achieved by selective functionalization of pillararene rims (Zhang et al., 2021;Al-Azemi & Vinodh, 2022;Vinodh et al., 2023). Selective derivatization of pillarene rims enables self-assembly of these macromolecules to form supramolecular polymers or make them capable of interacting with flexible binding sites, for example proteins (Liu et al., 2023). The suitably functionalized pillarenenes could conjugate with other functional units such as drug moieties or photosensitizing agents and might generate potentially useful functional materials for a variety of applications data reports such as drug delivery, light harvesting systems, sensors, detection and separation (Feng et al., 2017;Kakuta et al., 2018;Hua et al., 2020;Khalil-Cruz et al., 2021).
The inclusion complex crystallizes in the monoclinic crystal system, space group C2/c. The asymmetric unit contains half of the pillararene molecule ( Fig. 1) and half the guest molecule. The complete structure (Fig. 2) is obtained by symmetry expansion via crystallographic twofold axes. In the crystal, one molecule of dibromobutane is encapsulated within the cavity of the pillararene. The terminal alkene parts, which project outwards from the pillararene ring, exhibit positional disorder. As a result, the exact orientation of the vinyl groups with respect to the pillararene macrocycle could not be obtained from the crystal data. In Fig. 2 the orientation of the major occupancy butene component is shown.
The crystal structure of Pil(Butenoxy)2ÁButBr2 shows the that 1,4-dibromobutane guest species is threaded inside the pillararene cavity, forming a 1:1 inclusion complex. All of the H atoms of the guest molecule are capable of engaging in nonbonding interactions with pillararene ring, either via C-HÁ Á ÁO or C-HÁ Á Á interactions. In addition, the pillararene   Displacement ellipsoid representation (30% probability) of the asymmetric unit of Pil(Butenoxy)2ÁButBr2.
macrocycle is able to connect with the bromine atoms of the dibromobutane by C-HÁ Á ÁBr interactions. The nature of these various non-bonding interactions are depicted in Fig. 3 and their quantitative details are provided in Table 1. The Pil(Butenoxy)2ÁButBr2 species exhibit intermolecular non-bonding C-HÁ Á ÁO or C-HÁ Á Á interactions in their crystal network. The multiple non-bonding (non-covalent/ non-coordinate) interactions (less than the van der Waals range) between neighboring Pil(Butenoxy)2.ButBr2 systems are shown in Fig. 4. It can be seen that each pillararene unit interacts with six immediate neighboring pillararenes in its crystal network. The packing pattern of the Pil(Butenoxy)2ÁButBr2 complex is depicted in Fig. 5, which shows that the crystal network forms one-dimensional channels along the a-axis direction.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The vinyl site exhibits positional disorder and thus was refined over two sets of sites with a 0.52 (2):0.48 (2) occupancy ratio. Intermolecular non-bonding interactions between the pillararene macrocycle and its neighboring counterparts. C-HÁ Á ÁO interactions are represented by red and C-HÁ Á Á by blue dashed lines. Cg1 is the centroid of the pillararene phenyl ring C2-C7. Symmetry codes: (i) Àx, y,
Cg1 and Cg2 are the centroids of the C2-C7 and C9-C13 rings, respectively.    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.68 e Å −3 Δρ min = −0.60 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.