Formation of infinite grids with chiral square compartments by self-assembly of achiral 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acids.: Effect of 4,4′-substitution on the grid stacking

The achiral 1,1 ' -biphenyl-2,2 ' ,6,6 ' -tetracarboxylic acid as well as its 4,4 ' -dibromo and 4,4 ' -dinitro derivative self-assemble in crystal under formation of a two-dimensional grid set up from hydrogen-bonded cyclotetrameric compartments which are individually chiral (D-4 symmetry). The roughly square cavities (ca 5.6 Angstrom) of individual compartments partly accommodate the perpendicularly oriented benzene rings of the neighbouring grid, in dependence on the nature of the 4,4 ' -substituents. As a consequence, the grids are stacked in a staggered (nonconcatenated) manner.