Comment

In a previous publication, we investigated the thin-film characteristics of neutral pseudorotaxanes consisting of 1:1 and 1:2 mixtures of bis(1,5-naphtho)-38-crown-10 with N-alkyl derivatives of both pyromellitic diimide and 1,4,5,8-naphthalenetetracarboxylic diimide (Lynch et al., 1999). The Langmuir spreading solutions used in this study were subsequently refrigerated for storage while the paper was being refereed and published. These solutions, over a period of several months, eventually evaporated to dryness, yielding crystals of varying quality. From the solution containing a 1:1 molar mixture of the crown and N,N'-di-n-tetradecylpyromellitic diimide, two distinct crystal forms were identified, separated and characterized using single-crystal X-ray techniques. One of those structures was that of (I), reported here, while the other form was that of a second polymorph of the crown (Lynch & Hamilton, 2004a). From the solution containing a 1:1 molar mixture of the crown and the naphthalene diimide analogue, crystals were obtained which gave the structure of the diimide; however, the poor quality of the crystals led to poor data and hence a poor structure refinement (Lynch & Hamilton, 2004b).

The structure of (I) is similar to other compounds of this type, being essentially rod-shaped (Fig. 1) with the packing dominated by the lamellar arrangement of the molecules. The diimide moieties arrange in a classic herring-bone structure with two close non-hydrogen-atom contacts: C6O21(-x, -½  +  y, ½  -  z) = 2.874  (5)  Å and C2O61(x, ½  -  y, -½  +  z) = 2.946  (5)  Å. The chains are inclined at an angle of ca 40° to the plane of the diimide ring. The naphthalene diimide analogue similarly resides on an inversion centre, the molecules also pack in layers and the chains in this compound are also inclined at an angle of ca 40° to the plane of the ring system, but this structure differs from (I) in that the naphthalene moieties are parallel to each other, displaying interplanar distaces of ca 3.3-3.4  Å in the overlap regions.

Figure 1 The molecular configuration and atom-numbering scheme for (I). Displacement ellipsoids are drawn at the 50% probability level. For clarity, only the first and last C atoms of the alkyl chain have been labelled. [Symmetry code (i): -x, 1  -  y, 1  -  z.]

Experimental

Crystals of the title compound were obtained following the total evaporation of an equimolar mixture of bis(1,5-naphtho)-38-crown-10 and (I) in 10  ml chloroform (0.1  mg  cm^-3) at 277  K.