Dual fluorescence of syringaldazine.

The absorption and fluorescence spectra of syringaldazine (SYAZ) has been recorded in solvents of different polarity, pH and beta-cyclodextrin (beta-CD) and compared with syringaldehyde (SYAL). The inclusion complex of SYAZ with beta-CD is investigated by UV-vis, fluorimetry, AM 1, FT-IR, (1)H NMR and scanning electron microscope (SEM). DeltaG value suggests the inclusion process is an exothermic and spontaneous. In all solvents a dual fluorescence is observed for SYAZ, whereas, SYAL shows a dual luminescence only in polar solvents. The excitation spectra for the 410 nm is different from 340 nm indicate two different species present in this molecule. In pH solutions: (i) a large red shifted maxima is observed in the dianion and is due to large interactions between the aromatic ring and (ii) the large blue shift at pH approximately 4.5, is due to dissociation of azine group and formation of aldehyde. beta-CD studies reveal that, SYAZ forms a 1:2 complex from 1:1 complex with beta-CD.