Vibration‐Induced Emission (VIE) of N,N′‐Disubstituted‐Dihydribenzo[a,c]phenazines: Fundamental Understanding and Emerging Applications

Abstract

Organic fluorophores with dual‐emission and large Stokes shifts are attracting great attention due to their importance in fundamental research and technique applications. This Progress Report gives an account on how a novel luminescence mechanism termed vibration‐induced emission (VIE) is established. The VIE mechanism is coined for the rationalization of an alterable dual emission of V‐shaped N,N′‐disubstituded‐dihydribenzo[a,c]phenazines (DHPs), which are originated from a bent‐to‐planar vibration and the reverse in the excited state. The validation of the VIE mechanism is highlighted, such as the work reporting the utilization of chemically‐locked strategy to snapshot the excited‐state planarization of DHPs, and the application of the approach of steric hindrance‐induced planarization to tune the ground‐state geometry of DHPs. Moreover, the emerging applications of this VIE concept in photoelectric and biomedical disciplines are summarized. Additionally, further development of the VIE systems as well as the remaining challenges are prospected. This report could arouse wide interest from various fields to the specific area of VIE, which would not only broaden the VIE territory but also enlarge the scope of advanced functional materials.

Polymer-Stretching-Regulated Microscopic Photoluminescence of Vibration-Induced Emission (VIE) Molecules

“…Along with reacting to variations in the external surroundings, such as the solvent polarity, viscosity and temperature, the VIE molecules showed diverse emissions from blue to orange red through a gradual process; such emissions are inseparable from the successive changes in their conformations. The related mechanism has been fully studied in our previous reports (28)(29)(30)(31)(32)(33)(34)(35)(36). For further exploration, this research focused on microcosmic disclosure in polymer systems by photoluminescence regulation of VIE molecules (Fig.…”

“…Vibration-induced emission (VIE) (25)(26)(27), as an emerging photoluminescence mechanism, has drawn great attention in recent years owing to its tunable multicolor mission between different successive configurations. This mechanism has been attributed to the saddle-like VIE molecules of 9,14-diphenyl-9,14-dihydrodibenzo[a,c]-phenazine and its derivatives with consecutive conformations from bent to planar (28)(29)(30)(31), resulting in appealing multicolor mission (blue and orange red) from a single molecular entity. Under different external environmental conditions, such as solvent polarity (32,33), viscosity (34,35) and temperature (36), VIE molecules display excellent photoluminescence properties with favorable reversibility and controllable regulations (37,38).…”

The endeavor of vibration-induced emission (VIE) for dynamic emissions

“…3a ). 84 However, such a monotonous structure greatly restricts the development of VIE research both fundamentally and in applications. Therefore, there is an urgent need to exploit new VIE cores.…”

“…The VIE mechanism has been utilized as a persuasive rationalization for large Stokes shifts and full-colour-tunable fluorescence of DPAC and its analogues under various conditions. 84 In regular solutions ( Fig. 2c ), an excited molecule of DPAC transforms the configuration from a bent state to a planar state in S 1 , releasing a very weak blue emission (bent state) and prominent orange-red fluorescence (planar state).…”

Heterogeneous Conductance‐Based Locally Shape‐Morphable Soft Electrothermal Actuator

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appropriate for human-machine interactions and use in wearable devices, as they can handle soft materials and arbitrary shapes. [1][2][3] Soft actuators can be driven by mechanical, [4,5] optical, [6][7][8][9] chemical, [10] magnetic, [11][12][13] and electrical [14,15] stimuli but need to be actuated with an easily accessible power source for practical applications. Among them, electrical stimuli provided by electroactive and field-activated polymers such as electro-driven hydrogels [16] and ionic polymer-metal composites (IPMCs) [17] are considered to be the most suited for this purpose.

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