5,11,17,23,29,35-Hexa-tert-butyl-37,38,39,40,41,42-hexakis(ethoxycarbonylmethoxy)calix[6]arene acetonitrile disolvate

In the title compound, C90H120O18·2CH3CN, the calix[6]arene has a 1,2,3-alternate conformation and possesses inversion symmetry. It crystallizes as an acetonitrile disolvate, with a half-molecule of calix[6]arene and one molecule of solvent in the asymmetric unit. In the crystal, the two solvent molecules are enclosed in voids between the calix[6]arene molecules. They form weak C—H⋯O hydrogen bonds involving an O atom of the lower rim substituent. The cavity of the calix[6]arene itself is enclosed by two opposite phenol rings, which are turned into the cavity due to the presence of a C—H⋯π interaction. The calix[6]arene molecule exhibits disorder of one substituent on its lower rim [occupancy ratio 0.897 (3):0.103 (3)].

In the title compound, C 90 H 120 O 18 Á2CH 3 CN, the calix[6]arene has a 1,2,3-alternate conformation and possesses inversion symmetry. It crystallizes as an acetonitrile disolvate, with a half-molecule of calix [6]arene and one molecule of solvent in the asymmetric unit. In the crystal, the two solvent molecules are enclosed in voids between the calix[6]arene molecules. They form weak C-HÁ Á ÁO hydrogen bonds involving an O atom of the lower rim substituent. The cavity of the calix[6]arene itself is enclosed by two opposite phenol rings, which are turned into the cavity due to the presence of a C-HÁ Á Á interaction. The calix[6]arene molecule exhibits disorder of one substituent on its lower rim [occupancy ratio 0.897 (3):0.103 (3)].
The title compound crystallizes as a diacetonotrile solvate, with half a molecule of calix[6]arene and one molecule of acetonitrile in the asymmetric unit (Fig. 1). The molecular structure of the title compound is illustrated in Fig. 2. The acetonitrile molecule is bound to the calix[6]arene via a weak C-H···O hydrogen bond involving an O atom of a lower rim substituent (Table 1). Due to the presence of the oxygen atoms, the lower rim substituents are suitable acceptors of weak C-H···O hydrogen bonds (intra-and intermolecular) from surrounding bridging methylene (C7) and methyl (C15) groups (Table 1). The shape of the calix[6]arene cavity is influenced by the presence of C-H···π interactions between the methyl group of the tert-butyl group and the aromatic ring C1c-C6c (Table 1 and Fig. 3).

Experimental
The title compound was prepared following a previously published procedure (McKervey et al. 1985).

Refinement
Atoms (O3a,C14a,C15a), of the ethoxycarbonylmethoxy substituent on ring C1a-C6a, are disordered over two positions with an occupancy ratio of 0.897 (3) : 0.103 (3). Their positions were found from difference electron density maps. The disordered fragments were placed in appropriate positions, and all distances between neighbouring atoms were restrained, as well as the bond angles, to standard values. Site occupancies were refined for the different parts with the same thermal parameters for the same atoms in the various fragments. In the final cycles of refinement, the C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93, 0.97 and 0.96 Å for CH, CH 2 and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (parent C-atom), where k = 1.5 for CH 3 H-atoms and = 1.2 for other H-atoms.

Figure 1
A view of the asymmetric unit of the title compound with atom numbering. Displacement ellipsoids are shown at the 50% probability level.   A view along the a axis of the crystal packing of the title compound. The C-H···O hydrogen bonds are shown as dashed cyan lines (see Table 1 for details; H atoms not involved in these interactions have been omitted for clarity).
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. The positions of disorder atoms were found from the electron density maps. Disodered fragments were then placed in appropriate positions, and all distances between neighbouring atoms were restrained as well as angles. Site occupancies were refined for the different parts with the same thermal parameters for the same atoms in various fragments. The final partial occupancies were found 0.896 (3). At the end of refinement, hydrogen atoms were placed in calculated positions with the thermal parameters U iso (H) (in the range 1.2-1.5 times U eq of the parent atom)