Self-assembly of a luminescent Zinc(II) complex: a supramolecular host-guest fluorescence signaling system for selective nitrobenzene inclusion

Abstract

A luminescent Zn(II) complex, [Zn(bpy)(aba)₂] (1) {bpy = 2,2'-bipyridyl and aba = 4-dimethylaminobenzoate} has been synthesized as a white solid. Complex 1 shows unusually high selectivity toward nitrobenzene in the presence of other organic guests in solution, as well as in the vapor phase, resulting in both a dramatic color change and a concomitant quenching of luminescence. When crystallized from nitrobenzene, 1 affords deep red crystals with the composition [Zn(bpy)(aba)₂]·C₆H₅NO₂ (2) as a hydrogen-bonded channel structure via unusual intermolecular C-H···C(sp³) and H···H interactions. Inside the channels, nitrobenzene molecules form infinite polar linear tapes through strong C-H···O interactions in a head-to-tail fashion. The desorption and resorption of nitrobenzene can be achieved in a thermally reversible manner that can be monitored by X-ray powder diffraction patterns.