Fig. 4: Single crystal structures.

Crystal packing structures of (a) BO1a, (b) BO3a, (c) BO4b and (d) BO6. Double arrows represent the distance between two planes; dot lines represent the intermolecular C–H···π interactions.

Crystal packing structures of (a) BO1a, (b) BO3a, (c) BO4b and (d) BO6. Double arrows represent the distance between two planes; dot lines represent the intermolecular C–H···π interactions.