Harnessing Noncovalent Interactions for a Directed Evolution of a Six-Component Molecular Crystal

Building up on weak orthogonal interactions in supramolecular chemistry, a six-component crystal is designed. Using five distinctly different noncovalent forces, namely, hydrogen bonding, halogen bonding, cation-π, anion-π, and ion-pair interactions, three six-component crystals were designed with crown-ether (I), thiourea (II), 2,3,5,6-tetrafluoro-1,4-dibromobenzene (III), lone-pair donating anion (IV), ammonium cation (V), and electron-rich aromatic ring (VI). The M06-2X functional which is highly suitable in describing other weak interactions fails for ion-pairs. Tuned range-separated (RS)-DFT calculations are found to be capable in describing the ionic interactions in molecular solids. Molecular dynamics simulations show that the predicted multicomponent crystals are stable at room temperature and reducing the ionic charges for the ion-pairs destabilizes them. The strong electrostatic interactions between the three ion-pairs, NH₄⁺···ClO₄^-, NH₄⁺···HSO₄^-, and NH₄⁺···HCO₃^- is the primary driving force for the stabilization of the six-component crystal. Using a hybrid of strong and weak intermolecular interactions, one may generate exotic molecular complexity like n-component crystals.