Dual signaling of hypervalent iodine reagents by oxidative cleavage of a rhodamine-hydroxamic acid

A new 2-iodoxybenzoic acid (IBX)-selective probe based on rhodamine-hydroxamic acid was developed. The rhodamine-hydroxamic acid showed naked-eye detectable chromogenic and fluorogenic signaling for the versatile oxidant IBX. Signaling is due to an oxidative transformation of the rhodamine-hydroxamic acid by IBX. Signaling was not affected by the presence of common metal ions or anions. Selective signaling of IBX was possible in the presence of residual oxidants of bromate, hypochlorous acid, or Oxone. Rhodamine-hydroxamic acid exhibited similar signaling behavior toward other important hypervalent iodine reagents, Dess–Martin periodinane and [bis(trifluoroacetoxy)iodo]benzene, under similar measurement conditions. Convenient IBX-selective optical signaling with a detection limit of 1.4 × 10−6 M was realized.