Interactions edge-to-face

A number of papers deal with aspects of [Ru(phen)3] ". In the solid state, [Ru(phen)3] PF6]2 consists of racemic layers of cations, between which the anions reside. This contrasts with the structure of [Ru(bpy)3][PFg]2 which possesses homochiral layers. Racemic layers of [Ru(phen)3] " " cations are observed in the perchlorate salt. The structure of A-[Ru(phen)3][PF6]2 has been determined. Data for 335 M(phen), 159 M(phen)2, and 33M(phen)3 complexes from the Cambridge Structural Database have been analyzed and show that offset face-to-face inter-phen interactions are more common that edge-to-face interactions. ... 

The structure determination allows for an examination of the intermolecu-lar interactions of the three-component cocrystal (Fig. 17). Hydrogen bonding is observed between the carbonyls of BQ 21 and the hydroxyls of BN 20. A four-component u-stacking motif is apparent among two molecules each of BQ 21 and BN 20. Finally, edge-to-face interactions are observed with two molecules each of BQ 21 and AN 16. 

Fig. 14.1 Structures and crystalline order for benzene (1) and naphthalene (2) showing predominant edge-to-face interactions.

Fig. 14.2 Anthracene and its native solid-state order, showing edge-to-face interactions.

The addition of substituents to both the 9- and 10-positions of anthracene serves to disrupt the edge-to-face interactions of the molecule, preventing the adoption of a herringbone arrangement in the crystal. As long as the substituent groups are relatively small, the molecules will be able to adopt a n-stacked arrangement. 9,10-Dimethylanthracene (14) [28] and 9,10-bis(chloromethyl) anthracene (15) [29] are both excellent examples of the typical crystalline order of such species (Fig. 14.10). 

Fig. 21. Stereodrawing of L-arabinose bound to L-arabinose-binding protein from Escherichia coli. The edge-to-face interaction between tryptophan-16 and phenylalanine-17 gives rise to a hydrophobic surface that interacts with the hydrophobic portion of the sugar. Reproduced with permission from Quiocho and Vyas (1984).

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