Conjoining the benefits of an additional phenyl ring in a simple benzophenone hydrazone-based platform @ discriminatory recognition of F− over CN− with quantitation of aqueous Cu2+: New tricks for an old dog

Abstract

Herein, benzophenone hydrazone derived two π-conjugative networks viz.DMHMN and DMHMP have been judiciously designed for competitive recognition of F− (LOD: 6.8 ppm; Ka: 7.2 × 103 M−1) over CN− (LOD: ∼0.3 ppm; Ka: 20.3 × 104 M−1) along with Cu2+. Interestingly, the presence of an extra phenyl ring in DMHMN played a pivotal role for discriminative colorimetric recognition of F− over CN− despite having greater hydration energy of F−. Deliberate implantation of an extra phenyl ring leads to enhanced acidity of the benzophenone platform, rationalizing structure-performance synergies. While the presence of dangling OH group and azomethine functionality enables both the chemosensors to exhibit selective recognition toward Cu2+ in purely aqueous phase with the detection limit of ∼0.7 ppm and ∼0.16 ppm by DMHMP and DMHMN respectively, which are far below the safe limit set by World Health Organization (WHO). The sensing phenomenon by the redox non-innocent sensory receptors has been thoroughly investigated by UV–Vis, cyclic voltammetry and 1H NMR spectroscopic studies validated by density functional theory (DFT). Moreover, relay recognition of Al3+ by [DMHMN·F−] ensemble made it a suitable contender for complex logic circuitry fabrication like IMPLICATION/INHIBIT circuit. Additionally, the sensory probes have the capability of quantitative estimation of Cu2+ from unknown water samples, which was cross-examined with the help of the lab-based market available portable device. Lastly, smartphone assisted point-of-care testing (POCT) application has been performed for on-field detection of F− by DMHMN.