Selective Isolation of Polycyclic Aromatic Hydrocarbons by Self-Assembly of a Tunable N→B Clathrate

The combination of one dipyridyl linker [1,2-di­(4-pyridyl)­ethylene (DPE), 1,2-di­(4-pyridyl)­ethane (DPEt), or 4,4′-azopyridine (DPA)] with two molecules of arylboronate ester <b>1</b> produced dinuclear Lewis-type N→B adducts that can act as acyclic host for polycyclic aromatic hydrocarbons (PAHs) in the solid state. Nine crystalline solids of composition PAH@adduct (i.e., one PAH per adduct) were obtained from solutions containing a single PAH. On the basis of the single-crystal X-ray diffraction analysis of the compound ANT@A1 (ANT = anthracene; A1 = adduct being composed of DPE and two boronate esters <b>1</b>), the PAH inclusion selectivity is related to a size-fitting adaptation to an octaedral-shaped pocket assembled by CH-π interactions between fragments of the diamine and the arylboronate ester <b>1</b>. The resulting reversible organic clathrates can perform “catch and release” cycles of PAHs such as pyrene and can sequester selectively PAHs from mixtures in solution.