New calix[4]arene based oxalylamido receptors for recognition of copper(II)

New calix[4]arene derivatives with oxalylamido loops on their upper and lower rim (7, 8) have been designed and synthesized. It has been determined that molecular receptor 8 is more efficient than 7 for recognition of copper ions in preference to other metal ions through distinct ‘naked eye’ color change and a significant change in absorption spectra and fluorescence characteristics. The reported work paves the way for development of novel sensor materials for ubiquitous ions like copper at low concentrations.