Paintable Room‐Temperature Phosphorescent Liquid Formulations of Alkylated Bromonaphthalimide

Abstract

Organic phosphors have been widely explored with an understanding that crystalline molecular ordering is arequisite for enhanced intersystem crossing. In this context, we explored the room-temperature phosphorescence features of asolvent-free organic liquid phosphor in air.While alkyl chain substitution varied the physical states of the bromonaphthalimides,t he phosphorescence remained unaltered for the solvent-free liquid in air.A st he first report, as olvent-free liquid of al ong swallow-tailed bromonaphthalimide exhibits room-temperature phosphorescence in air.D oping of the phosphor with carbonyl guests resulted in enhanced phosphorescence,a nd hence al arge-area paintable phosphorescent liquid composite with improved lifetime and quantum yield was developed.Metal-free organic materials exhibiting room-temperature phosphorescence (RTP) have found use in various applications. [1, 2] Easy synthetic procedures as well as their structural tunability and air stability encourage the use of organic phosphors. [1][2][3][4][5][6] In recent years,o rganic small molecules decorated with various functional moieties,such as halogens, boronate esters,o rc arbonyl group, [3] have been explored in RTPm aterials.T hese structural modifications eventually resulted in efficient intersystem crossing towards stable phosphorescence.However,organic phosphors mostly exhibit excellent RTPi nt he crystalline state,r ather than in the solution state. [4] Strong control over the nonradiative decay in the rigid crystalline molecular packing supports intersystem crossing. Moreover,i tr educes the triplet quenching by placing the molecules at finite distances.I ns hort, RTPi n organic phosphors is mainly controlled by intermolecular interactions and the overall organization of the molecules in the crystal. In addition, efficient triplet emission has been established with the help of several other methods,s uch as doping with molecules containing heavy atoms and matrixassisted isolation using polymers,m icelles,o rc avitands. [5,6] Theavailability of asupport medium rigidifies the emitter and in turn strengthens the radiative relaxation process.D espite all of these developments,there are still many key points to be addressed in the design of efficient organic phosphors. Moreover,t he processability of these crystalline phosphors still constitutes achallenging problem. In this context, anew processable soft material called functional molecular liquid has been introduced as ar eplacement for solid luminescent materials. [7][8][9] Here the viscous medium increases the luminescence quantum yield by suppressing the nonradiative decay. [8e] As organic phosphors have mostly been tested in the crystalline form under inert conditions,R TP liquids have never been explored.Naphthalimides are aclass of rhylene dyes that have been widely exploited in self-assembly,l ight harvesting, sensors, organic electronics,etc. [10] Here we have chosen two alkylated 4-bromo-1,8-naphthlimidesshowing RTPinboth the crystalline and liquid state for their narrow si...

Versatile Induction of Efficient Organic‐Based Room‐Temperature Phosphorescence via Al‐DMSO Matrices Encapsulation

“…[ 20 ] However the large Δ E ST (singlet–triplet energy splitting) always subsidizes these organics unobservable RTP effect, and a few methods have been reported to overcome this obstacle. [ 7h,8c,21 ] Here, electron donor of Aba‐ x was attached to 1,8‐naphthalimide (18‐NI) and 2,3‐naphthalimide (23‐NI), respectively, to obtain two kinds of NNI derivatives sharing the same electron‐deficient NNI ring, namely Naba‐ x and Npaba‐ x ( x = o , m , or p ). Surprisingly, a yellow RTP with peaks centered at 548, 593, and 635 nm was obtained from Naba‐ x ( x = o , m , or p ) doped series in 1 with the highest τ p of 311.6 ms for Naba‐ o /‐Cl ( Figure a–c,g).…”

Solvent‐Free Luminous Molecular Liquids

“…Moreover, such LMLs often exhibit low viscosities. For instance, the LMLs of alkylated tetrazines and alkylated naphthalenes exhibit complex viscosities (η*) in the ranges of 28–58 and 38–67 mPa • s, respectively, which are much lower than the η* of alkylated oligo( p ‐phenylenevinylene)s (0.64–34.6 Pa • s), alkylated 9,10‐diphenylanthracenes (0.28–84.0 Pa • s), alkylated pyrenes (2.3–58.0 Pa • s), and an alkylated bromonaphthalimide (0.79 Pa • s) . Such low viscous LMLs are promising for developing refreshable devices owing to their facile refilling.…”

“…Quite recently, Babu's group reported the first room‐temperature metal‐free phosphorescent LML, BNT1 , using bromonaphthalimide as a phosphor . The attachment of long bulky alkyl chains resulted in a low T g (<−38.7 °C) of BNT1 , which behaves as a liquid at room temperature ( Figure a,b).…”

“…c) Photograph of a film of liquid BNT1 (coated on a quartz plate) under UV light irradiation (λ ex = 365 nm) after being dipped in liquid nitrogen for 10 s. d) Photograph of large area (10 × 10 cm) coating of BNT1 –terephthalaldehyde (1:1 mol%) liquid composite in air. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

“…Despite multifarious examples of RTP in the crystalline state, purely organic compounds showing RTP in solution are rare [ 64 – 69 ]. Takeuchi et al [ 28 ] reported a bromofluorenecarbaldehyde 2 which shows blue fluorescence in chloroform at 298 K under air and green phosphorescence under argon with a phosphorescence quantum yield of Φ P = 5.9% ( Fig.…”