A new ion pair receptor fulfilling a dual function as a chromogenic molecular switch for F− and ratiometric selective recognition of HSO4−

► 1 shows high selectivity for detecting F− in color change and spectra change. ► 1 functions as a chromogenic molecular switch by using combinations of F− and K+. ► 1 shows high selectivity for detecting HSO4− by the naked eye in 1·K+ complex. ► 1 shows selectivity for detecting HSO4− in ratiometric manner in 1·K+ complex. ► Titration experiment of 1 with HSO4− in case of K+ shows enhancement of affinities.