Synthesis of a Zn-salen resorcinarene-based cavitand and its fluorescence response to nitro compounds

<div><p>The synthesis, spectroscopic characterisation, conformational switching and fluorescence quenching efficiency of a resorcinarene-based cavitand containing Zn-salen (<b>Zn</b>-<b>Cav</b>) are reported. Synthesis of <b>Zn</b>-<b>Cav</b> was accomplished by the condensation of a quinoxaline derivatised with Zn-salen and a resorcinarene-based cavitand containing three quinoxalines. <sup>1</sup>H NMR spectroscopy confirmed that in DMSO, chloroform and acetone <b>Zn</b>-<b>Cav</b> resides in the vase conformation. The molecular geometry of <b>Zn</b>-<b>Cav</b> selectively changes from vase to kite under acidic conditions. Detection by fluorescence quenching of nitro-containing molecules, such as 4-nitrotoluene, 2,4-dinitrotoluene and 2,3-dimethyl-2,3-dinitrobutane was explored by spectrofluorimetry. It was found that the fluorescence of <b>Zn</b>-<b>Cav</b> is efficiently quenched by nitroaromatic compounds.</p></div>