Constructing Multi‐Stimuli‐Responsive Luminescent Materials through Outer Sphere Electron Transfer in Ion Pairs

Abstract

materials, which can be broadly applied as bioprobes, [2] environmental monitors, [3] optical data storage medium, [4] etc. Generally, the stimuli-responsive luminescent materials are designed based on an inner sphere mechanism for electron transfer, and there are very few examples of such materials based on the outer sphere electron transfer mechanism. In fact, the design and preparation of stimuli-responsive materials based on inner sphere electron transfer mechanism is more difficult because tedious synthetic procedures or complex covalent modifications are often involved (Figure 1a). Supramolecular interactions constructed materials can be considered as ideal candidates to overcome this limit. Ion pairs, particularly those in which one or both of the components are transition metal complexes, have attracted increasing attention recently. [5] The ion-paired materials are of practical importance in the development of organic light-emitting diode, [6] dye-sensitized solar cells, [7] catalysts, [8] chemical sensors, [9] as well as smart electronic devices. [10] Importantly, ionic donor− acceptor interactions may provide an outer sphere mechanism for electron transfer that would enable the construction of stimuli-responsive materials.Ionic phosphorescent iridium(III) complexes have received significant attention due to their appealing photophysical properties, such as high photoluminescence (PL) quantum yields, excellent photostability, significant Stokes shifts, and high sensitivity toward surrounding environments. [11] Among the various ionic iridium(III) complexes, bis-terpyridine iridium(III) complexes are one of the most attractive candidates for the formation of stimuli-responsive ion pairs due to the following features: i) rich photochemistry, complicated excited states, and remarkable photophysical properties are ideal for stimuli-responsive character, [12] ii) high cationic character (charge +3) enables strong electrostatic interactions between donor and acceptor, and iii) very high energy content in the excited states makes them powerful photo-oxidants, [13] ensuring efficient PET processes. Based on these facts, it was hypothesized that the emission intensity of a bis-terpyridine iridium(III) complex would be quenched by the addition of a strong electron donor via a PET process. Subsequently, the consumption Stimuli-responsive luminescent materials are of scientific and technological interest due to their wide range of optoelectronic applications. The utilization of photoinduced electron transfer (PET) reactions is an effective strategy to design various stimuli-responsive luminescent materials. To date, most of these materials are based on the inner sphere electron transfer mechanism, which refers to a redox chemical reaction that proceeds via a covalent bridge. In contrast, the method of using outer sphere electron transfer mechanism is superior to the covalent approach as it does not require tedious synthesis. Ion pairs, which are composed of two oppositely charged components, are ideal for t...

Information Storage Based on Stimuli‐Responsive Fluorescent 3D Code Materials

“…have been widely reported, involving a variety of stimuli responsiveness, for example, pH responsiveness, light responsiveness, electrical responsiveness, thermal responsiveness, humidity responsiveness, mechanical responsiveness, etc. [129][130][131][132][133][134] By incorporating various stimuli-responsiveness into one luminescent system, the luminescent properties of materials can be regulated in multi-level ways. This multi-regulation capability endows the luminescent materials with versatility, especially showing bright prospects in information storage and anti-counterfeiting.…”

Substituent-Adjusted Electrochromic Behavior of Symmetric Viologens

“…Electrochromic (EC) materials have attracted growing interest for researchers due to their extensive applications in displays [ 1 , 2 , 3 ], smart windows [ 4 , 5 , 6 , 7 , 8 ], anti-dazzling mirrors [ 9 , 10 , 11 ], and optical sensors [ 12 , 13 , 14 ]. By applying certain voltages, the optical properties of these materials can be reversibly regulated in the visible and the near-infrared regions.…”

Electroluminochromic Materials and Devices Based on Metal Complexes

“…To further verify the application of PeTm echanism in ELC, an ion pair was reported composing of an electron-deficient phosphor Ir-17 ( Figure 2) and an electron-rich quencher (tetrabutylammonium borohydride, BH 4 À ). [58] The emission intensity of phosphor Ir-17 enhanced significantly by the application of electricals timulus owing to the photoinduced reductive electron transfer process between the excited state of Ir-17 and BH 4 À (Figure 7a). The ELC characteristic wasv erified by immersingt he copper plate electrode in acetonitrile solution of [Ir-17,B H 4 À ] 2 + .T he solution exhibited weak emission near the cathodeb efore anda fter the voltage wasa pplied, and the emission intensity near the anode increased within several seconds at ab ias voltageo f5V.…”

“…To further verify the application of PeT mechanism in ELC, an ion pair was reported composing of an electron‐deficient phosphor Ir‐17 (Figure ) and an electron‐rich quencher (tetrabutylammonium borohydride, BH 4 − ) . The emission intensity of phosphor Ir‐17 enhanced significantly by the application of electrical stimulus owing to the photoinduced reductive electron transfer process between the excited state of Ir‐17 and BH 4 − (Figure a).…”

“…Reproduced with permission from Ref. . Copyright 2019 Wiley‐VCH Verlag GmbH & Co. TEM images for the Ir‐18 ‐capped (b) Au and (c) Ag nanoparticles.…”