Edge-to-face stack

The interactions among the conserved residues forming the surface of the pocket, and between these and a conserved second shell of residues, seem to orient several of the surface atoms for binding to ligand a chain of hydrogen bonds links Trp 153, Tyr 195, His 183, Tyr 98 and via a water molecule, Glu 190 Trp 153 is part of an edge-to face stack of aromatic rings with Phe 147 and Phe (or Tyr) 148. 

Fig. 2.28 Edge-to-face stacking and face-to-face stacking...

Fig. 2 Edge-to-face stacking in organic semiconductor molecules (a) co-crystallization strategy applied to a thiophene and anthracene and (b) solid-state packing of p-PTE." °...

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. 

Aromatic n n interactions (sometimes called n n stacking interactions) occur between aromatic rings, often in situations where one is relatively electron rich and one is electron poor. There are two general types of -interactions face-to-face and edge-to-face, although a wide variety of intermediate geometries are... 

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). 

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