Redox‐Guest‐Induced Multimode Photoluminescence Switch for Sequential Logic Gates in a Photoactive Coordination Cage

Abstract

Molecular or supramolecular level photoluminescence (PL) modulation combining chemical and photonic input/output signals together in an integrated system can provide potential high‐density data memorizing and process functions intended for miniaturized devices and machines. Herein, a PL‐responsive supramolecular coordination cage has been demonstrated for complex interactions with redox‐active guests. PL signals of the cage can be switched and modulated by adding or retracting Fc derivatives or converting TTF into different oxidation states through chemical or photochemical pathways. As a result, reversible or stepwise PL responses are displayed by these host–guest systems because of the occurrence of photoinduced electron‐transfer (PET) or fluorescence resonance energy transfer (FREnT) processes, providing unique nanodevice models bearing off/on logic gates or memristor‐like sequential memory and Boolean operation functions.

The Redox Coupling Effect in a Photocatalytic RuII‐PdII Cage with TTF Guest as Electron Relay Mediator for Visible‐Light Hydrogen‐Evolving Promotion

“…However,addition of TTF into MOC-16 solution gives rise to appearance of EPR signal even under natural sunlight, indicating oxidization of TTF into TTF +C radical. [52] Further addition of TEOAi nto above mixture causes disappearance of EPR signal, suggesting aquenching of TTF +C radical by electron interchange between TTF +C and TEOAs acrificing electron donor. Similar redox events were also observed for TET-TTF and TCN-TTF (Supporting Information, Figure S4).…”

“…ThePLquenching of MOC-16 by TTF could be contributed from host-guest electron transfer from TTF to Ru 2+ -based *MOC-16, in which the 3 MLCT excited state is interacted by redox TTF via areductive quenching procedure,while TTF itself is oxidized to TTF + C species. [50] Our previous PL titration study revealed ac irca 20-fold higher static quenching constant (K s ,3 2500 [mol L À1 ] À1 )than the dynamic constant (K c ,1561 [mol L À1 ] À1 ) for MOC-16 + TTF system, [52] suggesting that the PL quenching of MOC-16 by TTF is dominated by formation of hostguest complex, which forms the basis of synergistic coupling effect with TTF guest as photoredox mediator within the confined nanocage.I nc ontrast, TET-TTF/TCN-TTF just quench emission of MOC-16 slightly (Supporting Information, Figure S10), implying ar edox interacting role in bulk solution different from the host-guest system, which is consistent with the EPR results that electron transfer between MOC-16 and TET-TTF/TCN-TTF indeed occurs but the photocatalytic efficiencyisr educed obviously.…”

“…From above photophysical and photochemical studies,we tentatively propose amechanism for the redox coupling effect in present host-guest system with TTF as an electron relay to mediate photoredox cycle of MOC-16 for efficient photocatalytic H 2 evolution (Figure 1 [37] leading to H 2 production as well as recovery of [MOC-16-Ru] 2+ .Meanwhile,the oxidized TTF + C is reduced back to TTF by TEOA, completing the electron transfer relay cycles.Bythis way,the electron donation via TEOAt oT EOA + transformation can sustain the photoredox cycle of MOC-16 through TTF mediation, providing electrons continuously for long-term H 2 generation and protecting MOC-16 from direct interacting with detrimental TEOA. To act as competent electron relay mediator,confinement of TTF in nanocage is essential, which not only makes the redox coupling between Ru-based photoredox cycle and TEOA-to-TEOA + transformation efficient in immediate vicinity,but also avoids electron dissipation in bulk solution and possible interfering process of fluorescence resonance energy transfer (FREnT) [52] from *MOC-16 to free TTF + C to cause useless PL quenching. This also accounts for the reason that the system combining separate Ru-based photosensitizer and Pd-based catalyzer with TTF,orMOC-16 integrating photo-and catalytic activities but simply mixed with bulky TET-TTF and TCN-TTF without confinement, cannot display synergistic redox coupling effect for H 2 production.…”

The Redox Coupling Effect in a Photocatalytic RuII‐PdII Cage with TTF Guest as Electron Relay Mediator for Visible‐Light Hydrogen‐Evolving Promotion

“…However, addition of TTF into MOC‐16 solution gives rise to appearance of EPR signal even under natural sunlight, indicating oxidization of TTF into TTF +. radical . Further addition of TEOA into above mixture causes disappearance of EPR signal, suggesting a quenching of TTF +.…”

“…species . Our previous PL titration study revealed a circa 20‐fold higher static quenching constant ( K s , 32 500 [mol L −1 ] −1 ) than the dynamic constant ( K c , 1561 [mol L −1 ] −1 ) for MOC‐16+TTF system, suggesting that the PL quenching of MOC‐16 by TTF is dominated by formation of host‐guest complex, which forms the basis of synergistic coupling effect with TTF guest as photoredox mediator within the confined nanocage. In contrast, TET‐TTF/TCN‐TTF just quench emission of MOC‐16 slightly (Supporting Information, Figure S10), implying a redox interacting role in bulk solution different from the host‐guest system, which is consistent with the EPR results that electron transfer between MOC‐16 and TET‐TTF/TCN‐TTF indeed occurs but the photocatalytic efficiency is reduced obviously.…”