A series of donor−acceptor pyranones (3a−m, 4a−h) were synthesized using α-oxo-ketene-S,S-acetal as the synthon for their application as emissive materials for energy-saving organic light-emitting devices (OLEDs). Among them, five pyranones 3f, 3g, 3h, 3m, and 4e exhibited highly bright fluorescence in the solid state and weak or no emission in the solution state. Photophysical analysis of these dyes revealed that only 3f and 3m showed aggregation-induced emission behavior in a THF/water mixture (0−99%) with varying water fractions (f w ) leading to bright fluorescence covering the entire visible region, while other derivatives 3g, 3h, and 4e did not show any fluorescence signal. The computational studies of the compounds revealed that the longer wavelength absorption originates from HOMO to LUMO electronic excitation. These dyes exhibited good thermal stability with 5% weight loss temperature in the range of 218−347 °C. The potential application of the donor− acceptor pyranone dyads was demonstrated by fabrication of solution-processed OLEDs. Remarkably, OLED devices prepared using highly emissive compounds 6-(anthracen-9-yl)-4-(methylthio)-2-oxo-2H-pyran-3-carbonitrile (3m) and 6-(4-methoxyphenyl)-4-(methylthio)-2-oxo-2H-pyran-3-carbonitrile (3f) displayed pure white emission with CIE coordinates of (0.29, 0.31) and (0.32, 0.32), respectively. Additionally, the resultant devices exhibited external quantum efficiencies of 1.9 and 1.2% at 100 cd m −2 , respectively.

A facile synthesis and detailed photophysical investigation of E/Z-isomerization of fluorescent diphenylamine tethered stilbene derivatives (DPASs) under white light exposure have been carried out to understand the effect on fluorescence, electrochemical properties, and photostability under various activation/deactivation pathways. In solution state, in the dark, the E-isomer of DPASs (6a-d) exhibited high fluorescence quantum yields (Φ ≈ 53% to 60% in DMSO). However, on white light exposure, H NMR and HPLC studies revealed that pure E-isomer of the DPAS 6a (∼9.5 mM) started converting into its Z-form by photoisomerization until it reaches to nearly equilibrium. At low concentrations (∼10 μM), the absorption band of the pure E-isomer in the range of 350-450 nm gradually decreased to adopt Z-conformation 6a' until a photostationary state was reached. The structure of the E-isomer 6a was unequivocally confirmed by X-ray diffraction analysis. The synthesized DPAS compounds 6a-d possessed positive solvatochromic properties, two photon absorption properties, and good thermal stability. The electrochemical investigations using DPASs showed reversible oxidation resulting in formation of a stable radical cation. Owing to useful photophysical, electrochemical and thermal properties, these DPAS derivatives are suitable for their application in biomedical imaging as well as in fabrication of electroluminescent materials.

A new dual responsive “turn‐on” and “ratiometric” aggregation‐induced emission luminogen (AIEgen) 3‐formyl‐5‐(piperidin‐1‐yl)biphenyl‐4‐carbonitrile 6 a (FPBC 6 a) for selective detection of hydrazine in solution as well as in vapour phase is described. At a low concentration of 2.5 μm, the probe FPBC 6 a is non‐fluorescent (turn‐off) but remarkably lights up (turn‐on with blue emission) in the presence of hydrazine solution (0.25–25 μm). Interestingly, at higher concentrations, the nanoaggregates of FPBC 6 a (>25 μm, 99 % HEPES in DMSO) displayed ratiometric response in the presence of hydrazine with a remarkable hypsochromic shift from the green (500–550 nm) to blue regions (440–480 nm). Furthermore, a real application of FPBC 6 a was successfully demonstrated through the detection and visualization of hydrazine in live cervical cancer cells as well as using portable test strips.

Host materials having high triplet energies offer great commercial potential for the development of solution-processable high-performance phosphorescent organic light-emitting diodes (PhOLEDs). While plenty of vacuum-deposited host materials are available, the literature reveals a dearth of solution-processable host materials. Therefore, a series of biarylcarbazoles (BACs) were designed as host materials by incorporating donor–acceptor functionalities and doped with blue, green, yellow, and orange phosphorescent emitters to develop energy-saving high-performance PhOLEDs with low turn-on voltages. All of the synthesized host materials exhibited good thermal stability in the range of 294–355 °C and exhibited remarkably high triplet energies of 2.50–2.81 eV. Surprisingly, PhOLEDs prepared by incorporating a host material 6a doped with a green phosphorescent emitter, i.e., Ir(ppy)3, displayed admirable efficiencies with a maximum power efficiency (PE) of 55.6 lm/W, a current efficiency (CE) of 53.2 cd/A, and an external quantum efficiency of 17.1% with a maximum brightness (L max) of 27 000 cd/m2. BAC host material 6a exhibited better performance compared to that of commercial host 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 4,4′,4″-tris(carbazol-9-yl)triphenylamine. The BAC 6a host was also found to be compatible with orange, yellow, and blue phosphorescent emitters, which displayed PEs of 31.9, 21.4, and 14.1 lm/W, respectively, at a brightness of 100 cd/m2. Notably, the green PhOLED with donor–acceptor-based host 6a exhibited 23% roll-up in CE while moving from 100 to 1000 cd/m2. The enhancement of the performance of the green PhOLED is attributed to higher singlet and triplet energies of host 6a compared to that of the utilized green emitter tris(2-phenylpyridine)iridium(III), leading to effective host–guest energy transfer and the ability to form efficient excitons in the host–guest matrix, thus enhancing the OLED performance. Thus, BAC 6a has commercial potential as a suitable host material for the fabrication of efficient multicolor PhOLEDs.