ABSTRACT
Methods to separate molecules (e.g., petrochemicals) are exceedingly important industrially. A common approach for separations is to crystallize a host molecule that either provides an enforced covalent cavity (intrinsic cavity) or packs inefficiently (extrinsic cavity). Here we report a self-assembled molecule with a shape highly biased to completely enclose space and, thereby, pack efficiently yet hosts and allows for the separation of BTEX hydrocarbons (i.e., benzene, toluene, ethylbenzene, xylenes). The host is held together by N â B bonds and forms a diboron assembly with a shape that conforms to a T-shaped pentomino. A T-pentomino is a polyomino, which is a plane figure that tiles a plane without cavities and holes, and we show the molecule to crystallize into one of six polymorphic structures for T-pentomino tiling. The separations occur at mild conditions while rejecting similarly shaped aromatics such as xylene isomers, thiophene, and styrene. Our observation on the structure and tiling of the molecular T-pentomino allows us to develop a theory on how novel synthetic molecules that mimic the structures and packing of polyominoes can be synthesized and-quite counterintuitively-developed into a system of hosts with cavities used for selective and useful separations.
ABSTRACT
A method to obtain single crystals of the opioid antagonist naloxone in the free base form is facilitated using mechanochemistry. The application of mechanochemistry reduces the number of steps and makes single crystals readily available from solution compared to using an approach based exclusively on solution or the reported method based on sublimation. The X-ray structure confirms the structure determined using powder diffraction and provides details of hydrogen bonding.
ABSTRACT
Self-assembled complexes utilizing the ditopic dative bond acceptor 1,3-diboronic acid with catechol and complementary U-shaped donors in the form of 1,8-dipyridylnaphthalenes (1,8-bis(4-pyridyl)naphthalene (DPN), 1,8-bis(4-ethylenylpyridyl)naphthalene (DEPN), and 1,8-bis(4-ethynylpyridyl)naphthalene (DAPN)) yielded discrete two-component structures. The assemblies exhibit "plug-in-socket" geometries. DFT calculations are consistent with the donor pyridyl and acceptor catecholate being electron poor and rich, respectively. The assemblies pack via π-π interactions and support the inclusion of a solvent (i.e., DPN, DAPN). The materials may form a basis for the design of complex B-based structures (e.g., supramolecular dyads).
