A fluorescent AND logic gate based on a ferrocene-naphthalimide-piperazine format responsive to acidity and oxidizability

Abstract

A novel fluorescent molecular logic gate 1 is demonstrated as a two-input AND logic gate for the detection of acidity and oxidizability. Designed according to an electron-donor-spacer-fluorophore-spacer-receptor' format, the modules are represented by ferrocene as the electron donor, 1,8-naphthalimide as the fluorophore and piperazine as the proton receptor. In the presence of elevated concentrations of H + and Fe 3+ , the molecule switches 'on' emitting at λ max = 530 nm with Φ f = 0.060 at 10 −4 M H + and 50 μM Fe 3+. The H + binding and apparent Fe 3+ binding constants determined by fluorimetric titrations in 1:1 (v/v) methanol/water are log β H+ = 8.1 and log β Fe3+ = 4.7. Modulation of the fluorescence output results from controlling competing photoinduced electron transfer (PET) at the ferrocene end and internal charge transfer (ICT) at the piperazine end. Time-resolved fluorescence spectroscopy reveals a single fluorescent lifetime of 5.8 ns, while from absorption transient spectroscopy a remarkable fast decay signal < 2 ps is observed. Comparison is made with methylpiperazine 2 and piperazine fluorescent pH indicator 3 as model compounds.

Recent Progress on the Evolution of Pourbaix Sensors: Molecular Logic Gates for Protons and Oxidants

“…Rearrangement of the modules, as exemplified by 5, in the order 'electron-donor-spacer 1 -fluorophore-spacer 2 -receptor' improved device performance to yield a 16-fold switching enhancement and a Φ f of 0.09. A sister molecule with piperazine instead of methylpiperazine as the proton receptor switches 6-fold with an Φ f of 0.06 [28]. The shorter distance for charge transfer between the ferrocene and the excited state fluorophore is a favorable factor as is the ππ* ICT state, which causes a dipole moment in the photoexcited state [29].…”

Fluorescence for biological logic gates

“…Several materials have been created to respond with a changed FLT to a single condition, such as with temperature [85] or with viscosity [35,86], and some to respond to single chemical inputs, such as glyphosate [44], pH [34], or various ions [87]. Others developed nanostructures that respond by FLT or a combination of FI and FLT to describe various logic operations following exposure to multiple inputs [26,[88][89][90][91]. Some researchers did create probes responding to various chemical inputs and used the FLT to differentiate situations, but ultimately relied only on the FI for logic gate determination [36,[92][93][94][95][96][97].…”

A Highly Water-Soluble and Solid State Emissive 1,8-Naphthalimide as a Fluorescent PET Probe for Determination of pHs, Acid/Base Vapors, and Water Content in Organic Solvents

“…As a result, the PET process was recently tested extensively in the most common fluorophores and a large number of PET-based probes were reported. In addition, the PET process and the "fluorophore-spacer-receptor" format were involved even in the more complicated molecular logic devices for multicomponent analysis [29][30][31][32]. However, the synthesis of PET chemosensing probes with improved properties and better applicability is still a major task.…”