All the solvents and reagents (analytical grade and spectroscopic
grade) were obtained from SigmaeAldrich and used as received. 1H
NMR was performed on a Varian 400 MHz spectrometer and
chemical shifts are recorded in parts per million (ppm). Electrospray
ionization mass spectra (ESI-MS) were collected on a Thermo
Finnigan (San Jose, CA, USA) LCQTM Advantage MAX quadruple ion
trap instrument. Elemental analysis for carbon, nitrogen, and hydrogenwas
carried out by using a Flash EA 1112 elemental analyzer
(thermo) in Organic Chemistry Research Center of Sogang University,
Korea. Absorption spectra were recorded at room temperature
using a PerkineElmer model Lambda 2S UV/vis spectrometer.
Fluorescence measurements were performed on a PerkineElmer
model LS45 fluorescence spectrometer.