Molecular Design Tactics for Highly Efficient Thermally Activated Delayed Fluorescence Emitters for Organic Light Emitting Diodes

Recently, pure organic thermally activated delayed fluorescence (TADF) emitters have attracted considerable interest from the scientific community in the field of organic light emitting diodes (OLEDs) as they can theoretically realize 100 % of the internal quantum efficiency by exploiting both the singlet and triplet excitons via the reverse intersystem crossing enabled by small singlet‐triplet energy splitting. Currently, the external quantum efficiency of the TADF emitters is reaching the level of phosphorescent emitters. Therefore, the TADF approach is considered as a potential alternative to the low efficiency conventional fluorescent and expensive phosphorescent emitters. In this account, we summarized our recent development of blue and green TADF molecular designs to improve the device performances of the TADF devices.     

Kinetics of the dissociation of tris(1,10-phenanthroline) iron(III) complex ion in aqueous acid solutions. A mechanistic model for product specificity

Summary The natural decay of Fe(phen) _f3 ^p3+ , where no Ce^IV is employed for scavenging the side reaction product, Fe(phen) _f3 ^p2+ , is now treated as a complex reaction involving two parallel processes, and the experimental kinetics are consistent with the rate laws derived from a mechanism that simultaneously explains the composition of the products as a function of acidity. In terms of the proposed mechanism the dissociation rate of the complex ion in acid solutions containing Ce^IV as scavenging agent is to be regarded as a Ce^IV retarded aquation rate, and OH^– is to be assigned a catalytic role in the kinetics of basic reduction.     

Neoteric Advances in Oxygen Bridged Triaryl Boron-based Delayed Fluorescent Materials for Organic Light Emitting Diodes

Since their first demonstration, thermally activated delayed fluorescence (TADF) materials have been emerged as the most promising emitters because of their promising applications in optoelectronics, typified by organic light-emitting diodes (OLEDs). In which, the rigid oxygen bridged boron acceptor-featured ( DOBNA ) emitters have gained tremendous impetus for OLEDs, which is ascribed to their excellent external quantum efficiency (EQE). However, these materials often displayed severe efficiency roll-off and poor operational stability. Therefore, there needs to be a comprehensive understanding of the aspect of the molecular design and structure-property relationship. To the best of our knowledge, there is no detailed review on the structure-function outlook of DOBNA -based emitters emphasizing the effect of the nature of donor units, their number density, and substitution pattern on the physicochemical properties, excited state dynamics and OLED performance were reported. To fill this gap, herein we presented the recent advancements in DOBNA -based acceptor featured TADF materials by classifying them into several subgroups based on the molecular design i. e. donor-acceptor (D−A), D−A-D, A−D-A, and multi-resonant TADF (MR-TADF) emitters. The detailed design concepts, along with their respective physicochemical and OLED performances were summarized. Finally, the prospective of this class of materials in forthcoming OLED displays is also discussed.     

Decoration of Dibenzofuran Using Cyanocarbazole via 6‐Position as a Molecular Design Approach for High‐Triplet‐Energy Bipolar Host Materials

In this study, two new dibenzofuran derivatives featuring one or two cyanocarbazole units, 6‐(dibenzo[b,d]furan‐4‐yl)‐9‐phenyl‐9H‐carbazole‐3‐carbonitrile ( mBFCzCN) and 6,6′‐(dibenzo[b,d]furan‐4,6‐diyl)bis(9‐phenyl‐9H‐carbazole‐3‐carbonitrile) ( dBFCzCN ), were developed as host materials for phosphorescent organic light emitting diodes (PhOLEDs). A new molecular design connecting the cyanocarbazole to the dibenzofuran using the cyanocarbazole 6‐position instead of its 9‐position was created, and the effects of number of cyanocarbazole units in the dibenzofuran building block on the photophysical and electroluminescence properties were investigated in detail. The mBFCzCN compound revealed high triplet energy (2.78 eV) than that of dBFCzCN (2.68 eV) and good bipolar charge transporting properties. The potential of these materials as hosts for blue and green PhOLEDs was investigated using bis(4,6‐(difluorophenyl)pyridinato‐N,C^2′)picolinate iridium(III) (FIrpic) and tris(2‐phenylpyridinato)iridium(III) (Ir(ppy)₃) dopants, respectively. The results indicated that the mBFCzCN with one cyanocarbazole unit showed better device performance than the dBFCzCN with two cyanocarbazole units in the blue and green devices. High external quantum efficiencies of 19.0 and 21.2 % were demonstrated in the blue and green PhOLEDs with the mBFCzCN host due to its high triplet energy and good bipolar charge transporting characteristics.     

An alternative total synthesis of Patulolide A

A new total synthesis of [R]‐Patulolide A from readily available (R)‐propylene epoxide obtained using the asymmetric synthetic approach is reported. The key reactions involved are ozonolysis and Yamaguchi macrolactonization, resulting in the ring system.     

Triggering Thermally Activated Delayed Fluorescence by Managing the Heteroatom in Donor Scaffolds: Intriguing Photophysical and Electroluminescence Properties

Establishment of the structure–property relationships of thermally activated delayed fluorescence (TADF) materials has become a significant quest for the scientific community. Herein, two new donors, 10H‐benzofuro[3,2‐b]indole (BFI) and 10H‐benzo[4,5]thieno[3,2‐b]indole (BTI), have been developed and integrated with a aryltriazine acceptor to design the green TADF emitters benzofuro[3,2‐b]indol‐10‐yl)‐5‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)benzonitrile ( BFICNTrz ) and 2‐(10H‐benzo[4,5]thieno[3,2‐b]indol‐10‐yl)‐5‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)benzonitrile ( BTICNTrz ), respectively. The physicochemical and electroluminescence properties of the compounds were tuned by exchanging the heteroatom in the donor scaffold. Intriguingly, the electronegativity of the heteroatom and the ionization potential of the donor unit played vital roles in control of the singlet–triplet energy splitting and TADF mechanism of the compounds. Both compounds showed similar singlet excited states that originated from the charge transfer (CT) states (¹CT), whereas the triplet excited states were tuned by the heteroatom in the donor unit. The origin of phosphorescence in the BTICNTrz emitter was CT emission from the triplet state (³CT), whereas that in the BFICNTrz emitter stemmed from the local triplet excited state (³LE). Consequently, BTICNTrz showed a small singlet–triplet energy splitting of 0.08 eV, compared with 0.26 eV for BFICNTrz . Thus, BTICNTrz showed efficient delayed fluorescence with a high quantum yield and a short delayed exciton lifetime, whereas BFICNTrz displayed weak delayed fluorescence with a relatively long lifetime. Furthermore, a BTICNTrz ‐based device exhibited a maximum external quantum efficiency (EQE) of 15.2 % and reduced efficiency roll‐off (12 %) compared with its BFICNTrz ‐based counterpart, which showed a maximum EQE of 6.4 % and severe efficiency roll‐off (55 %) at a practical brightness range of 1000 cd m^?2. These results demonstrate that the choice of subunit plays a vital role in the design of efficient TADF emitters.     

Synthesis,biological evaluation and molecular docking studies of novel 2-(2-cyanophenyl)-N-phenylacetamide derivatives

A series of novel 2-(2-cyanophenyl)-N-phenylacetamide derivatives 3(a-u) were designed and synthesized via selective amidation of methyl-2-(2-cyanophenyl)acetates over amidine formation by using AlMe₃ as catalyst in good yields. All the newly synthesized derivatives were well characterized by ¹H NMR, ¹³C NMR, FTIR and HRMS spectral techniques. All the synthesized title compounds were evaluated for their in vitro anticancer activity against three cancer cell lines. Among all compounds, 3i (IC₅₀?=?1.20 μM, IC₅₀?=?1.10 μM), 3j (IC₅₀?=?0.11 μM, IC₅₀?=?0.18 μM), 3o (IC₅₀?=?0.98 μM, IC₅₀?=?2.76 μM) showed excellent inhibitory activity than the standard Etoposide (IC₅₀?=?2.11 μM, IC₅₀?=?3.08 μM) against MCF-7 and A-549 cell lines, respectively. Docking analysis of all the compounds with the human topoisomerase II revealed that the compound 3j fitted well in the active site pocket, showing the best docking score of 158.072 kcal/mol.