The ligand, 1H,5H-benzo (1,2-d:4,5-d′)bistriazole (H2-BBTA), was synthesized as described previously. All other chemicals were of reagent grade and used as received from the commercial supplier. Fourier-transform infrared spectra were recorded in the range of 180-4000 cm -1 or on a Bruker Equinox 55 FT-IR spectrometer equipped with an ATR unit. The intensity of the bands was assigned as strong (s), middle (m) and weak (w).