Signaling preferences of substituted pyrrole coupled six-membered rhodamine spirocyclic probes for Hg(2+) ion detection.

Two six-membered spirocyclic rhodamine derivatives containing substituted pyrroles (1 and 2) were shown to exhibit preferential dual mode 'turn-on' signaling responses in the presence of Hg(2+) ions through complexation mediated spiro-ring opening. Although the rate of spiro-ring opening mediated through complexation is much slower in these probes in comparison to their five membered analogues, they exhibited a comparable sensitivity in metal ion detection.