Furthermore, the IR spectra of RATU and RATU-Hg2+ were recorded (Fig. 11). Compared to the IR spectrum of RATU, the disappearance of the peak at 1668.38 cm−1 (Cdouble bond; length as m-dashO) in the IR spectrum of RATU-Hg2+ indicated the opening of the spirolactam ring and the variation of the carbon-oxygen double bond (Cdouble bond; length as m-dashO) to the carbon-oxygen single bond (Csingle bondO). The vanishing of the peak at 1118.68 cm−1 (Cdouble bond; length as m-dashS) matched the removal of HgS. The shift of the peak from 3352.19 to 3448.63 cm−1 and its great enhancement manifested the formation of the single bondNH2 groups. At the same time, the peaks between 1636 and 1467 cm−1 (corresponding to the phenyl and Nsingle bondH groups) as well as the peaks from 1398 to 1180 cm−1 (related to the Csingle bondO and Csingle bondN groups) were changed obviously in the IR spectrum of RATU-Hg2+, which is also consistent with the speculation that Hg2+ was first bound by S atom, and then HgS and phenyl left to give the new compounds RATU′.