Extended Data Fig. 5. Derivatization of JF₆₆₉.

(a) Reaction of azide 21 with strained alkynes 25 or 26 to form triazole adducts 27 or 28. (b) Synthesis of amine 22 via reaction of JF₆₆₉ (15) with NH₃, reduction of azide 21, or Curtius rearrangement starting from ester 29 showing consistent regioselectivity of S_NAr reactions. (c) Reaction of 15 with amine-containing chelator groups 30 and 31 to form far-red K⁺ indicator 32 and far-red Zn²⁺ indicator 33. (d) Fluorescence emission spectra of 32 in the absence or presence of 100 mM K⁺. (e) Fluorescence emission spectra of 30 in the absence or presence of 10 μM Zn²⁺.