Redox‐Enabled, pH‐Disabled Pyrazoline–Ferrocene INHIBIT Logic Gates

Abstract

Pyrazoline-ferrocene conjugatesw ith an "electron-donorspacer-fluorophore-receptor" format are demonstrated as redox-fluorescent two-input INHIBIT logic gates.Molecular logic-basedc omputation is now firmly established as am aturing research discipline with researchers contemplating pragmatic uses for this curiosity-based science. [1][2][3][4][5] Medicalrelated innovations such as photodynamic photosensitizers, [6] drug delivery systems [7] and multi-analyte diagnostics [8] are but af ew envisioned applications. One of our visions is the realization of logic gates responsive to the physiochemical parameters of pH and potential( pE), which are fundamental to understanding metal ion solubility in geology and metallurgy as well as in medicine. [9] The development of reliable fluorescentc hemosensors and logic gates for open-shell d-metal ions, particularly Fe 3 + ,r equires overcoming several challenges including issues of solubility.[10] The vast majority of studies in this field continuet ob e reported in organic solvents, where Fe 3 + can form aqua-coordinated speciest hat act as unsuspecting weak acids.[11] Consequently,c omplexation or redox chemistry is often inferred, when matter-of-fact the fluorescent response is due to acidbase chemistry.[12] Furthermore, it is commonly taken for granted that in water Fe 3 + hydrolyses to insoluble Fe(OH) 3 above pH 4. [13] With an understanding of these issues, [10] the applicability of pE-pH logic gates in an applied setting is ar eal possibility.F or example, the detection of Fe 3 + under acidic conditions by fluorescencec ould become ar outine method for the early detection of corrosion of ferrous alloys such as steel. [14] Wu and colleagues have demonstrated an oteworthy logic gate responsive to pH andr edox chemistry.[15] The prototype consisted of ad imethylaniline moiety (protonr eceptor) attached to aP t II complexedt erpyridyl (by av irtual spacer) linked to af errocenyl acetylide (electron donor). From ad esign point of view,t his molecule exemplifies am olecular device with an "electron-donor-fluorophore-spacer-receptor" format. The logic gate exhibited an INHIBIT function with H + and Fe 3 + as the inputs and absorbance at 405 nm as the output. The mechanism of operation involved photoinduced electron transfer (PET) from the dimethylaniline unit and am etal-toligand charget ransfer from the ferrocenyl acetylide. Understandably,b eing ap roof-of-concept, the study wasp erformed in acetonitrile.Herein we now presente xamples of pyrazoline-ferrocene conjugates 1-3 with an ovel "electron-donor-spacer-fluorophore-receptor" format for the first time (Figure 1). In contrast to the example by Wu, we illustrate pE-pH INHIBIT logic gates with an ew structuralc onfiguration (the spaceri sl ocated between the electron donor and fluorophore rather than between the fluorophore and receptor) with fluorescencer ather than absorbance as the output and in 1:1( v/v)m ethanol/water rather than in acetonitrile.At the 5-position of the pyrazoline ring, 1-3 have aferrocene (electro...

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

“…In contrast, the maximum Φ f of 1 is a more modest 0.060 even on protonation and oxidation, while in the absence of both input conditions the minimum Φ f is 0.004 at pH 10. We observed a similar trend on comparing pyr azoline based fluorescent pH probes with pyrazoline ferrocene INH logic gates [34]. The cause of this limitation of fluorescent enhance ment is not fully understood.…”

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

“…Quenching of the fluorescent occurs at 10 −1 M acid due to protonation of the N2 atom. We capitalized on this known deactivation pathway to demonstrate H + -driven ternary 'off-on-off' logic with 10 [41] and H + , Fe 3+ -driven INHIBIT logic with 11 [42] (Figure 3). The latter logic result comes from an enhanced fluorescent signal at low proton and high oxidant threshold levels.…”

“…The latter logic result comes from an enhanced fluorescent signal at low proton and high oxidant threshold levels. While the H + -driven indicator 10 has a fluorescence quantum yield of 0.38 and a fluorescence enhancement of 20 [41], the redox-enabled pH-disabled logic gate 11 registers a remarkable 120-fold fluorescent enhancement, but with only 0.012 quantum yield output [42] in aqueous methanol. Experiments with stronger oxidants and inert electrodes should enhance the fluorescence output.…”

Supra-molecular agents running tasks intelligently (SMARTI): recent developments in molecular logic-based computation

“…reasonable distance from a reactive site in the study of substituent effects in physical organic chemistry. 49,50 More complex logic functions such as 'off-on-off' 51 and INHIBIT 52 are produced by derivatizing 1 or 2 within the 'fluorophore-spacer-receptor' frame of reference.…”