The present study offers a facile route for the synthesis of unsymmetrical hexasubstituted benzenes bearing alternate heteroatoms (O, S and Se) with the formula [1,3,5-(RSeCH2)3-2,4,6-(R'ECH2)3C6] (E = O, S or Se). The synthetic protocol involves the use of an in situ generated tris(selenonium) ion followed by treatment with another nucleophile affording the targeted species in >70% yields. The unsymmetrical hexasubstituted derivatives were characterized on the basis of physicochemical and spectroscopic data and in a representative case with single crystal X-ray study. The current work assumes great significance as the potential of these species as "turn-off" chemical sensors for Cu2+, which is a biologically and environmentally crucial metal ion, was also successfully demonstrated by 5a which bears alternate oxygen and selenium centres.