Start Nat cam tube

Nat cam tube

Pale-yellow crystals suitable for X-ray analysis grew by slow evaporation of a methanol solution of 1 at room temperature (r.t.) for 1 week.

Herein we report the synthesis and host properties of molecular tube 1 which presents a hydrophobic cavity encircled by polyaromatic anthracene panels (Fig. The tube is obtained by the transition-metal-free cross-coupling reaction of end-functionalized, bent compounds with two embedded anthracene rings.

The girded cylindrical cavity (~1 nm in diameter and length) of tube 1 selectively binds long hydrocarbons with branched methyl groups and/or unsaturated moieties, such as 2,2,4,4,6,8,8-heptamethylnonane (4a), nervonic acid methyl ester (5a), squalene (6a) and coenzyme Q4 (6c) (Fig.

The tubular framework is able to move along the long hydrocarbon chains on the NMR timescale (~0.1 s) so that proton peaks for the end of the chains were also shifted upfield.

The structure of 1 was unambiguously confirmed by X-ray crystallographic analysis.

For example, when branched 2,2,4,4,6,8,8-heptamethylnonane (4a; 2.2 μmol) and linear n-nonane (4b; 2.2 μmol) were suspended in a 1:1 D=−2.08 p.p.m., due to shielding effects from the encircling anthracene rings.

The 1:1 host–guest ratio was supported by ESI-TOF MS measurement, where a prominent signal was observed at m/z=843.8 corresponding to a [1·4a−2Cl ion.

The host–guest structure revealed that the bound alkane with branched methyl groups fully occupies the cavity of the tube with multiple CH–π interactions (Fig. Linear alkanes such as 4b, n-dodecane (4c) and n-hexadecane (4d) were also bound by tube 1 under similar conditions to give host–guest complexes 1·4b, 1·4c and 1·4d (92, 46 and 12% yields, respectively). (e) Molecular structure of 1·4a: the framework of tube 1 is the crystal structure (substituents are omitted for clarity) and the structure of bound 4a is optimized by semiempirical calculation (PM3 level).