Rare Example of TICT Based Optical Responses for the Specific Recognition of Cr3+ by a 2,2′:6′,2″-Terpyridine Derivative and Demonstration of Multiple Logic Operations

Chemosensor L showed a nonlinear fluorescence response on specific binding to Cr 3+ ion in the presence of various alkali, alkaline-earth, transition, and lanthanide metal ions. A luminescence band with maxima at 512 nm for L was observed (λ ext = 330 nm) for a twisted intramolecular charge transfer (TICT) transition following antienergy gap law behavior. However, normal energy gap law behavior prevailed on formation of a new nonluminescent charge transfer complex, M n + · L . For paramagnetic metal ions, paramagnetism induced luminescence quenching could have also contributed to this. A new switched on fluorescence response at λ ems of 356 nm (λ ext of 330 nm) was observed due to Franck–Condon charge transfer (FC-CT) transition only on the formation of a complex, (Cr 3+ ) 2 · L . Spectral studies revealed a unique dynamic coordination behavior and migration of Cr 3+ from the terpyridyl fragment to the N NMe 2 center of L as a function of the varying concentration of another ion (Zn 2+ ) and the subtle difference in the binding affinities of the terpyridyl moiety toward Cr 3+ and Zn 2+ . Further, spectral responses of L toward Zn 2+, different concentration of Cr 3+, H + and on subsequent addition of F – as different ionic inputs could be correlated well for demonstrating various basic and combinatorial circuits.