Crystal structure of (6E,20E)-3,24-difluoro-13,14,28,29-tetrahydro-5H,22H-tetrabenzo[e,j,p,u][1,4,12,15]tetraoxacyclodocosine-5,22-dione

The conformation of the title compound is cone-shaped, partially determined by short intramolecular C—H⋯O contacts. In the crystal, molecules are linked via C—H⋯O and C—H⋯F hydrogen bonds and C—H⋯π interactions, forming a three-dimensional supramolecular structure.


Chemical context
Macrocyclic compounds are known for their various applications, particularly in coordination chemistry (Delgado;1995). The study of synthetic macrocyclic compounds is an important area of chemistry in view of their presence in many biologically significant naturally occurring metal complexes. Such compounds have received special attention because of their presence in many important biological systems such as metallo-porphyrins (for example haemoglobin, myoglobin, cytochromes, chlorophylls), corrins (vitamin B12) and antibiotics (valinomycin, nonactin) with antibiotic, antifungal, anticancer and immunosuppressive activities as seen for erythromycin (McGuire et al., 1952;Woodward et al.;1981), amphotericin B (Vandeputte et al., 1956;Nicolaou et al., 1988), epithilone B (Gerth et al., 1996;Bode & Carreira; and rapamycin (Vezina et al., 1975;Smith et al., 1997). In addition, macrocyclic compounds having ether linkages and chalcone moieties have important applications (Rina et al., 2012, Matsushima et al., 2001. In this context the title compound was prepared and herein we report on its synthesis and crystal structure.

Structural commentary
The title compound, Fig. 1, has a cone-shaped conformation, partially determined by intramolecular C-HÁ Á ÁO short contacts (Table 1 and Fig. 1). The benzene rings at the top of the cone (C11-C16 and C31-C36) are inclined to one another by 73.10 (7) , while the benzene rings at the bottom of the cone (C21-C26 and C41-C46) are inclined to one another by 35.49 (8) (Fig. 2). The bond lengths and angles are similar to those observed in one of the starting materials for the synthesis of the title compound, viz. 2,2 0 -[ethane-1,2-diylbis(oxy)]dibenzaldehyde (Aravindan et al., 2003;Zhang et al., 2003); both measured at room temperature. A low temperature (120 K) structure analysis of the same compound has also been reported (Akkurt et al., 2013).

Supramolecular features
In the crystal, molecules are linked by C-HÁ Á ÁO and C-HÁ Á ÁF hydrogen bonds, forming a three-dimensional supramolecular structure ( Fig. 3 and Table 1). There are also C-HÁ Á Á interactions present, involving inversion-related molecules, within the three-dimensional framework (Table 1).

Database survey
A search of the Cambridge Structural Database (Version 5.37, update May 2016;Groom et al., 2016) indicated the presence of the subunit 1,2-bis(2-vinylphenoxy)ethane in a number of macrocyclic-type compounds. However, no macrocyclic-type compounds were found containing the subunit 2,2 0 -[ethane-1,2-diylbis(oxy)]dibenzaldehyde. The title compound, which contains both these subunits, is unique; no other reports of molecules of this type were found. A view of the molecular structure of the title compound, with atom labelling and 50% probability displacement ellipsoids. The short intramolecular C-HÁ Á ÁO contacts are shown as dashed lines (see Table 1).

Figure 2
A CPK model of the title compound, illustrating the cone-shaped conformation.

Figure 3
The crystal packing of the title compound, viewed along the b axis. Hydrogen bonds are shown as dashed lines (see Table 1), and for clarity only the H atoms involved in hydrogen bonding have been included.

Synthesis and crystallization
The title compound has been synthesized by two methods, illustrated in Fig. 4.
Method (b): Ultrasound-assisted synthesis Compound A (0.55 mmol, 0.15 gm) was dissolved in ethanol (5 ml) and added to a solution of compound B (0.55 mmol) in ethanol (5 ml), and solid NaOH (0.3 gm) was added to the mixture. The mixture was then irradiated in the water bath of an ultrasonic cleaner at room temperature for 20 min. The mixture solidified and the product was separated by filtration under vacuum, washed with ethanol, dried and purified by recrystallization from chloroform solution (yield 74%). Single crystals were obtained by slow evaporation of a dilute solution of the title compound in chloroform over 13 days at room temperature (m.p. 553-554 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were positioned geometrically and refined using a riding model: C-H = 0.95-0.99 Å with U iso (H) = 1.2U eq (C).     Table 1 Hydrogen-bond geometry (Å , ).