Modification of Fluorescent Photoinduced Electron Transfer (PET) Sensors/Switches To Produce Molecular Photo‐Ionic Triode Action

Abstract

The fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 system (where receptor 2 alone is photoredox-inactive) shows ionically tunable proton-induced fluorescence off-on switching, which is reminiscent of thermionic triode behavior. This also represents a new extension to modular switch systems based on photoinduced electron transfer (PET) towards the emulation of analogue electronic devices.Fluorescent photoinduced electron transfer (PET) sensors/ switches [1][2][3][4] are a well-established application of molecular devices, to the point of real-life deployment worldwide in blood electrolyte diagnostics. [5][6][7][8] Important picosecond laser studies on fluorescent PET sensors/switches have demonstrated the transient existence of radical ion species, [9][10][11] and thus designers can proceed with confidence. As a result of their modular fluorophore-spacer-receptor construction, fluorescent PET systems are very amenable to modification in terms of the format, as well as in terms of the detailed functionalities. The latter approach has yielded many individual examples of sensors and switches based on fluorescence which target important analytes. [12][13][14][15] On the other hand, the former approach has the potential to set up new areas of endeavor and application, which is exploited here.The controllable quenching of molecular fluorescence [1,2] can be exploited to build switchable systems which emulate familiar electronic devices. Some of these molecular systems have unique applications which are inconvenient for their electronic counterparts, such as wireless operation in micrometric spaces. [16] The first molecular logic gate [17][18][19][20][21][22][23] 1 (an advanced molecular switch [24] ) was a fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 system, [25,26] where two photoinduced electron transfer (PET) [4, 27] channels arising from the two receptors were controlled by binding H + and Na + ions, respectively, and thus the fluorescence output corresponded to photo-ionic AND logic. Strong fluorescence emerges only when all PET processes are suppressed (Figure 1 a). [4] Related, but distinct, fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 systems, [28] where both receptors respond to H + ions, for example, 2, give rise to fluorescent off-on-off action, which can correspond to ternary logic behavior. [22] We now demonstrate aspects of molecular photo-ionic triode action for the first time by structurally mutating the fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 system 1 into a novel format exemplified by 3, where the convenient photoredox capability of receptor 2 is removed from 1 (Figure 1 b). Nearly 20 distinct formats of luminescent PET switching systems, each possessing its own defining features and applications, are known. [26] Fluorescence off-on switching is, therefore, controlled within 3 by selective ion binding of receptor 1 . This switching profile is influenced by the orthogonally selective ion binding of receptor 2 , which is forced into a secondary role...

Platforms Formed from a Three-Dimensional Cu-Based Zwitterionic Metal–Organic Framework and Probe ss-DNA: Selective Fluorescent Biosensors for Human Immunodeficiency Virus 1 ds-DNA and Sudan Virus RNA Sequences

“…The above results may be rationalized from the unique structure of compound 1 . Its zeta potential of +7.9 mV indicates that it is positively charged. − Thus, compound 1 can absorb both P-DNAs through electrostatic, π-stacking, and/or hydrogen-bonding interactions to form P-DNA@ 1 complexes, , and thus quench the fluorescence of the FAM moiety via a PET process. ,, In the fluorescence recovery, the channel size of compound 1 may play a critical role in effectively distinguishing ss-DNA from triplex DNA and DNA/RNA duplex. , Because of the large cross-sectional areas and relatively rigid structures, the formed DNA triplex and DNA/RNA duplex cannot easily enter the pore of compound 1 . Meanwhile, the single-strand moieties of P-DNAs having smaller cross-sectional areas and conformational flexibility should be able to “induce fit” to interact with compound 1 strongly and thus can readily enter the pore and closely interact with the surface of compound 1 through multiple noncovalent interactions. , Furthermore, compound 1 may have less affinity for rigid triplex DNA and duplex DNA/RNA because of the absence of unpaired bases and the rigid conformation of triplex DNA and duplex DNA/RNA .…”

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Sugar‐based Molecular Computing by Material Implication

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