Role of spacer in single- or two-step FRET: studies in the presence of two connected cryptands with properly chosen. uorophores

Two cryptand molecules are connected via p-xyloyl, benzene-1,4-dicarbolyol and 9,10-dimethylene anthracene. Each cryptand is further derivatized with. uorophores such that electronic absorption of one. uorophore overlaps emission of the other. This way, three different systems L-1, L-2 and L-3 have been synthesized to get a better view of the effect on the distance in single-and two-step fluorescence resonance energy transfer (FRET) process. These molecules are probed for FRET in the presence of a metal ion as input. L-1 and L-2 exhibit poor performance in single step FRET while in the case of L-3, a large two-step FRET process is operational with Cu(II) or Hg(II) as input.