Uv vis u 3501 spectrophotometer

Ninhydrin, p–cresol, HMTA (Hexamethylenetetramine), TFA (Trifluoroacetic acid), N, N-Diethylethylenediamine was purchased from Sigma–Aldrich, Kolkata, India, urea purchased from Merck, Kolkata, India and all were used as received. The salts of the cations were also purchased from Sigma Aldrich, Kolkata, India. Solvents for the syntheses were purchased from commercial sources and used as received. ¹H and ¹³C NMR spectrum were recorded in DMSO-d₆ with TMS as internal standard on a Bruker, AV300 Supercon Digital NMR system with dual probe. The FT–IR spectra were recorded from KBr pellets in the range of 400–4000 cm⁻¹ on a Perkin-Elmer Spectrum 100 spectrometer. Elemental analyses for C, H and N were performed on a Perkin–Elmer 2400 II analysers. The ESI-MS experiments were performed on Waters Xevo G2-S QTOF mass spectrometer. The absorption and emission spectral studies were performed on a Hitachi UV–Vis U–3501 spectrophotometer and a Perkin–Elmer LS55 fluorimeter, respectively. Time-resolved fluorescence lifetime measurement were performed in Horiba Jobin Yvon Fluorocube-01-NLtime-correlated single photon counting (TCSPC) set up with picosecond delta diode (DD–375L) operating at λ_ex = 480 nm and a repetition rate of 1 MHz as excitation source.