1,3-Alternate conformer 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(4-methylsulfanylbenzyloxy)-2,8,14,20-tetrathiacalix[4]arene

The title thiacalix[4]arene derivative, C72H80O4S8, adopts a 1,3-alternate conformation, where the four 4-methylsulfanylbenzyl groups are located alternately at the two sides of a virtual plane defined by the four bridging S atoms. In the crystal, there are no significant intermolecular interactions present. Some of the peripheral tert-butyl and methylsulfanyl groups are disordered over two positions. A region of disordered electron density, occupying voids of ca 700 Å3 for an electron count of 124, was treated using the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155].

The title thiacalix [4]arene derivative, C 72 H 80 O 4 S 8 , adopts a 1,3-alternate conformation, where the four 4-methylsulfanylbenzyl groups are located alternately at the two sides of a virtual plane defined by the four bridging S atoms. In the crystal, there are no significant intermolecular interactions present. Some of the peripheral tert-butyl and methylsulfanyl groups are disordered over two positions. A region of disordered electron density, occupying voids of ca 700 Å 3 for an electron count of 124, was treated using the SQUEEZE routine in PLATON [Spek (2009). Acta Cryst. D65, 148-155].

Related literature
For a similar compound adopting a 1,3-alternate conformation, see: Xu et al. (2008). For background to thiacalix[4]arene derivatives, see: Kumagai et al. (1997); Morohashi et al. (2006); Yamato et al. (2006). For background to multidentate methylthioethers, see: Maye et al. (2005); Lim et al. (2007); Yan et al. (2010). For the synthesis, see: Morohashi et al. (2003).  (Kumagai et al., 1997). The ability of the parent phenolic thiacalix [4]arenes, as well as of their chemically modified derivatives obtained by the substitution of the phenolic H atoms with various types of ligating groups, to bind metal ions is well established (Morohashi et al., 2006). With thiacalix[4]arenes, the substituents frequently immobilize the molecule in a single conformation: cone, partial cone, 1,2-or 1,3-alternate. The ability to control inter-particle spatial properties of nanoparticle assemblies is one of the major challenges for the design and understanding of functional nanostructures. As a molecular linker, multidentate thioethers have been exploited for such control (Maye et al., 2005).

Crystal data
The viability of inter-particle linkages via coordination of the methylthio groups of arylethynes to gold surfaces was demonstrated recently in our laboratory (Lim et al., 2007;Yan et al., 2010). Multi-functional groups is the common characteristic of these molecular linkers. The 1,3-alternate conformer thiacalixarene derivative is an ideal molecular linker for assembling nanoparticle clusters. With this in mind, we synthesized the title compound, the first example of a thiacalix[4]arene derivative containing multidentate methyithioethers, and we report herein on its crystal structure.
The molecular structure of the title molecule is shown in Fig 1. The macrocycle adopts a 1,3-alternate conformation in which four substituent groups are located alternately above and below the virtual plane defined by four bridging sulfur atoms, S1-S4. The 1,3-alternate conformation thus appears to be regular and two pairs of opposite phenolic units are almost parallel to each other, but the substituent groups are inclined to one another. Comparable conformations were found in methyl ester derivatives (Xu et al., 2008), whereas the title tetra-benzyl ether derivative is much more distorted as a result of increased steric hindrance.

Refinement
Some of the peripheral -SCH 3 and t-butyl groups are disordered over two positions. These include the S-CH 3 groups involving atoms S5-C48, S6-C56, S7-C64 and S8-C72, and the t-butyl groups involving atoms C18-C20, C28-C30 and C38-C40; details are available in the archived CIF. A region of disordered electron density occupying voids of ca. 700 Å 3 , for an electron count of 124, was treated using the SQUEEZE routine in PLATON (Spek, 2009). It was not taken into consideration during refinement. The C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms: C-H = 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and = 1.2U eq (C) for other H atoms.

Computing details
Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  A view of the molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Only the major components of the disordered peripheral groups are shown.  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.