All reagents and solvent were purchased from commercial
source and used without further purification, if not stated. All
reactions were carried out on the magnetic stirrers and their reaction
process was monitored on thin layer chromatography (TLC).
Absorption and fluorescence spectra were taken on a Shimadzu
UV-1800 spectrophotometer and a Hitachi F-2700 fluorescence
spectrometer, respectively. 1H NMR and 13C NMR measurements
were recorded at 600 and 150 MHz on a Brucker Avance 600-
MHz spectrometer. Dimethyl sulfoxide (DMSO-d6) was solvent, and
tetramethylsilane (TMS) was used as internal standard. A pH meter
(Mettler Toledo, Switzerland) was used to determine the pH values.
HRMS (ESI) were taken on a Fourier transform ion cyclotron
resonance mass spectrometry (Varian 7.0T)