Colorimetric detection of in situ metal acetates and fluorides by a bipyridyl-linked Schiff base

Here, we present a new bipyridyl moiety linked Schiff base (bipy-1) that is well characterized using spectroscopic techniques. Colorimetric and UV-vis titrations were used to study the photophysical properties of bipy-1 in the presence of various tetrabutyl ammonium salt of anions and metal salts containing different counter cations. bipy-1 showed selective recognition of dimethyl sulphoxide solution of tetrabutyl ammonium salt of F(-) ion accompanied with a UV-vis band at 529 nm and interesting binding of aqueous Co, Ni, and Cu acetates/fluorides, as confirmed by distinct color changes from fluorescent green to pink or orange and a strong band around 480-510 nm in the UV-vis spectrum. However, in the presence of Co, Ni, and Cu countercations, any form of metal acetate/fluorides was found to be able to respond to similar color changes from fluorescent green to pink or orange, showing a band around 480-510 nm. This type of output clearly indicates that the in situ formation of Co, Ni, and Cu acetates/fluorides also coordinates with bipyridyl nitrogen atoms.