Dichlorosubstitution as a steering tool in hydrogen bonded cocrystals: the nature of rigid and flexible coformers in crystal structures

Abstract

Dichlorosubstitution is known to steer crystal packings of planar aromatic compounds into short-axis β-structures. We employed the combinatorial matrix analogy of six isomeric dichlorophenols with two distinct coformers to identify the critical structural determinants, like (a) the O–H⋯N synthon and its variations; (b) weaker, subsidiary non-covalent interactions (C–H⋯Cl, Cl⋯Cl, Cl⋯π, and Cl⋯O) in the context of isolable crystal packings. We synthesized and structurally characterized 13 co-crystals obtained from two coformers, planar 1,10-phenanthroline (110phe) and flexible 4,4′-bipyridine (44bp). Systematic studies of these co-crystals demonstrated the utilities of dichlorosubstitution at molecular scaffolds to tune crystal packings, to explore chiral packing in achiral substrates and to apply geometrical complementarities (planar vs. flexible) in exploring uncharted crystallization routes of the given binary systems.