Interpenetrating chiral 2D grid nets: hetero- versus homochiral 3D polycatenation in the crystal self-assembly of (RS)- and (R)-1,1′-binaphthalene-2,2′,6,6′-tetracarboxylic acids

Crystallographic analysis of the title binaphthyl tetracid 2 revealed unique propensity to polycatenation upon crystallization of both the enantiomerically homogeneous as well as the racemic form of the axially chiral tecton. Stereochemical aspects of the polycatenation have been analyzed in three conceptual steps, (i) formation of infinite 2D grids set up from hydrogen-bonded tecton cyclotetramers, (ii) stacking of the 2D grids, and (iii) interpenetration of the resulting stacks. In the crystal self-assembly of the enantiomerically uniform tecton, all three steps are homochiral. Conversely, in the crystal of the racemic tecton the homochiral self-assembling algorithm operates only in the steps (i) and (ii), giving rise to separate, antipodal, stacks of homochiral 2D layers. In the final step (iii), the antipodal stacks mutually interpenetrate, yielding racemic 3D polycatenated architecture within a single crystal.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide

(−)-(R)-1,1′-Binaphthalene-2,2′,6,6′-tetracarboxylic acidC24H14O8Ee = 100%[α]D20=-61.5 (c 0.17, methanol)Source of chirality: synthesis, (−)-mentholAbsolute configuration: aR