Sequential Recognition of Bisulfate and Acetate by a Ruthenium(II) Complex: Experimental and Theoretical Studies

New complex [RuLCl2(PPh3)] (L=N,N-bis(2-hydroxy-5-nitrobenzaldehyde)-2,2'-diaminodiethylamine) was prepared and characterized analytically and was employed as a luminescent chemosensor for the detection of anions. The results show that [RuLCl2(PPh3)] can detect HSO4- and AcO- selectively and in sequential order in H2O-CH3CN (8 : 2, v/v) at pH 7.0. The spectral binding, titration, and interference analyses reveal that the addition of HSO4- to [RuLCl2(PPh3)] results in an intense fluorescence emission (IF/I0=6.55). This shows that HSO4- interacts suitably with the complex to switch ON the fluorescence which could be explained by inhibition of a PET mechanism as the above addition forms [RuLCl(HSO4)(PPh3)] in the excited state. Selectivity interaction of complex [RuLCl2(PPh3)] with HSO4- results in the formation of [RuLCl(HSO4)(PPh3)] in water but the system exhibits negligible change in its emission except for AcO-, which enhances fluorescence intensity. For the addition of AcO- to [RuLCl2(PPh3)], the system [RuLCl(AcO)(PPh3)] is formed, however, the adding of HSO4- to [RuLCl(AcO)(PPh3)] does not show any change in the intensity, suggesting that there exists a logic gate function for the addition of HSO4- followed by AcO- to [RuLCl2(PPh3)]. This finding is interesting because [RuLCl2(PPh3)] can act as a fast selective chemosensor for the sequential detection of HSO4- and AcO-. The ruthenium(II) complex [RuLCl2(PPh3)] (L=N,N-bis(2-hydroxy-5-nitrobenzaldehyde)-2,2'-diaminodiethylamine) was prepared and characterized and has been employed as a luminescent chemosensor for the detection of anions. The complex performs efficiently to recognize selectively HSO4- and AcO- ions, increasing the fluorescence emission intensity.image