GUEST-BINDING PROPERTIES OF ORGANIC CRYSTALS HAVING AN EXTENSIVE HYDROGEN-BONDED NETWORK - AN ORTHOGONAL ANTHRACENE-BIS(RESORCINOL) DERIVATIVE AS A FUNCTIONAL ORGANIC ANALOG OF ZEOLITES [Review]

摘要

When recrystallized from an appropriate solvent, orthogonal bis(resorcinol)-anthracene compound 1a as host forms molecular sheets involving an extensive hydrogen-bonded network. This generates supramolecular cavities which incorporate two molecules of recrystallization solvent such as ketones and esters as guests via host-guest hydrogen-bonding. The guest incorporation under competitive recrystallization conditions is highly selective; even a difference by one methylene group in the guests can be-discriminated. The supramolecular cavities with included guest molecules are connected with each other, giving more or less continuous channels. Heating host-guest adducts in vacuo affords polycrystalline guest-free apohost. The apohost binds ketone and ester guests not only as liquids but also as gases and solids. The host:guest stoichiometry is 1:2 in most cases. Solid-state complexation using a 1:3 or 1:4 (host to guest) mixture affords 1:2 host-guest cocrystals and 1 or 2 equiv of unreacted guest simply remains as such. The adducts 1a . 2(guest) thus obtained under solid-liquid, solid-gas, or solid-solid conditions exhibit essentially the same powder X-ray diffraction patterns as their authentic single crystals. Apohost 1a also binds hydrocarbons and haloalkanes such as benzene, p-xylene, and chloroform again in a 1:2 (host to guest) molar ratio. These results demonstrate that guest molecules can diffuse in the crystal lattices of apohost 1a. As compared with the corresponding recrystallization processes, guest-binding to preformed apohost is apparently far less selective with respect to the guests. This is due to a kinetic preference for smaller guests, even without a hydrogen-bonding site as in hydrocarbons, which are capable of more facile lattice diffusion. The sorption-desorption of liquid and gaseous guests can be repeated many times. The guest-binding properties of apohost 1a is discussed from a viewpoint of a functional organic counterpart of porous inorganic crystal zeolites. [References: 107]