Syntheses and dye-binding abilities of novel calix[4]benzocrowns with π-conjugate azo groups on sidechains

Three novel calix[4]benzocrowns with π-conjugate azo groups on sidechains were designed and synthesized in ideal yields. Their structures and conformations were characterized by IR, 1H NMR, ESI–MS, elemental analysis. Their complexation abilities for dyes were investigated by liquid–liquid extraction experiments, complexation UV–Vis spectra and complexation ESI–MS spectra. The complexation experimental results suggested that they possessed excellent extraction abilities towards dyes. The highest extraction percentage of compound 3a for neutral red was 89.5 %. The complexation UV–Vis spectra of compounds 3a–c with four dyes indicated the 1:1 complexes between host and guest in DMSO solution. The association constant of compound 3b with OI was as high as 3.93 × 106 M−1. The complexation ESI–MS spectrum of compound 3c for Neutral red also supported the 1:1 complexes of host and guest. The complexation experiments showed these novel calix[4]arene receptors possess excellent complexation capabilities for dyes.