Hg2+-promoted photoactivation of triazolyl rhodamine.

Hg(2+) was able to induce the ring-opening of glycosyl triazolyl rhodamines after 26 h incubation at room temperature in MeCN-DMSO (99 : 1). This reaction can be dramatically accelerated by irradiation at 313 nm, by reducing the response time to 2 min. Selectivity towards Hg(2+) has also been demonstrated, except for Cu(2+), other metal ions showed almost no influence on this photochromic process. Detailed mechanistic investigations indicated that a small amount of DMSO played an important role during the photochromic transformation, probably by stabilising the excited open form of the triazolyl rhodamine-Hg(2+) complex.