New Light on an Old Story: Breaking Kasha’s Rule in Phosphorescence Mechanism of Organic Boron Compounds and Molecule Design

In this work, the phosphorescence mechanism of (E)-3-(((4-nitrophenyl)imino)methyl)-2H-thiochroman-4-olate-BF2 compound (S-BF2) is investigated theoretically. The phosphorescence of S-BF2 has been reassigned to the second triplet state (T2) by the density matrix renormalization group (DMRG) method combined with the multi-configurational pair density functional theory (MCPDFT) to approach the limit of theoretical accuracy. The calculated radiative and non-radiative rate constants support the breakdown of Kasha’s rule further. Our conclusion contradicts previous reports that phosphorescence comes from the first triplet state (T1). Based on the revised phosphorescence mechanism, we have purposefully designed some novel compounds in theory to enhance the phosphorescence efficiency from T2 by replacing substitute groups in S-BF2. Overall, both S-BF2 and newly designed high-efficiency molecules exhibit anti-Kasha T2 phosphorescence instead of the conventional T1 emission. This work provides a useful guidance for future design of high-efficiency green-emitting phosphors.

Transformation Rule-Based Molecular Evolution for Automatic Gasoline Molecule Design

Automatic molecular design on computers is an emerging technology for the determination of optimal fuel molecules. We developed a computer-aided molecular design framework through a transformation rule-based molecular evolution method. The reaction rule was used as the elementary step to change the molecular structure. A molecule can achieve structural variation continuously using a series of reaction rules. The finding of the optimal molecule can be seen as the evolution of structure in the chemical space, which was guided by using a global optimization algorithm to select the best reaction routine. We showed that the optimized molecule is independent of the input initial structure, proving the robustness of the method. We then applied the method to design gasoline molecules for motor and aviation gasoline. The designed molecules can not only serve as competitive candidate components for high-quality gasoline, but also accelerate the synthesis rate of new molecules in the laboratory.

Completely non-fused electron acceptor with 3D-interpenetrated crystalline structure enables efficient and stable organic solar cell

Non-fullerene acceptors (NFAs) based on non-fused conjugated structures have more potential to realize low-cost organic photovoltaic (OPV) cells. However, their power conversion efficiencies (PCEs) are much lower than those of the fused-ring NFAs. Herein, a new bithiophene-based non-fused core (TT-Pi) featuring good planarity as well as large steric hindrance was designed, based on which a completely non-fused NFA, A4T-16, was developed. The single-crystal result of A4T-16 reveals that a three-dimensional interpenetrating network can be formed due to the compact π–π stacking between the adjacent end-capping groups. A high PCE of 15.2% is achieved based on PBDB-TF:A4T-16, which is the highest value for the cells based on the non-fused NFAs. Notably, the device retains ~84% of its initial PCE after 1300 h under the simulated AM 1.5 G illumination (100 mW cm−2). Overall, this work provides insight into molecule design of the non-fused NFAs from the aspect of molecular geometry control.

Synthesis and Characterization of Conducting Polymer

In recent technology, considerable attention was given to the fabrication of light weight rechargeable batteries, electro chromic display devices, microelectronics, sensor and molecule design etc. As one of the most important conducting polymers, polyaniline because of its chemical stability and relatively high conductivity and its derivatives have been extensively studied in different fields of science, because of the demand for high performance materials in advanced technologies. However, the common uses of polyaniline are restricted, due to its poor process ability and low solubility. Various techniques were given for synthesis of conducting polymer. In the current studies, polyaniline (PANI) and its composites with semiconductor was prepared chemical oxidation method in the presence of different bronsted acids from aqueous solutions. The effect of thermal treatment on electrical conductivity (DC), of the pure PANI, PANI+10%, 15% and 20% MnSO4 conducting polymers were investigated. It is found that conductivity of PANI enhancing due to stretching polymeric chain cause due to interaction with MnSO4.

Hard and soft Lewis-base behavior for efficient and stable CsPbBr3 perovskite light-emitting diodes

All-inorganic CsPbBr3 perovskite is an attractive emission material for high-stability perovskite light-emitting diodes (PeLEDs), due to the high thermal and chemical stability. However, the external quantum efficiencies (EQEs) of CsPbBr3 based PeLEDs are still far behind their organic–inorganic congeners. Massive defect states on the surface of CsPbBr3 perovskite grains should be the main reason. Lewis base additives have been widely used to passivate surface defects. However, systematic investigations which relate to improving the passivation effect via rational molecule design are still lacking. Here, we demonstrate that the CsPbBr3 film’s optical and electrical properties can be significantly boosted by tailoring the hardness–softness of the Lewis base additives. Three carboxylate Lewis bases with different tail groups are selected to in-situ passivate CsPbBr3 perovskite films. Our research indicates that 4-(trifluoromethyl) benzoate acid anion (TBA−) with the powerful electron-withdrawing group trifluoromethyl and benzene ring possesses the softest COO− bonding head. TBA− thus acts as a soft Lewis base and possesses a robust combination with unsaturated lead atoms caused by halogen vacancies. Based on this, the all-inorganic CsPbBr3 PeLEDs with a maximum EQE up to 16.75% and a half-lifetime over 129 h at an initial brightness of 100 cd m−2 is thus delivered.

An I(I)/I(III) Catalysis Route to the Heptafluoroisopropyl Group: A Privileged Module in Contemporary Agrochemistry

The heptafluoroisopropyl group is emerging as a privileged chemotype in contemporary agrochemistry and features prominently in the current portfolio of leading insecticides. To reconcile the expansive potential of this module with the synthetic challenges associated with preparing crowded, fluorinated motifs, I(I)/I(III) catalysis has been leveraged. Predicated on in situ generation of p-TolIF2, this route enables the direct difluorination of α-trifluoromethyl-β-difluoro-styrenes in a single operation. This formal addition of fluorine across the alkene π-bond is efficient (up to 91%) and is compatible with a broad range of functional groups. The ArCF(CF3)2 moiety is conformationally pre-organized, with the C(sp3)-F bond co-planar to the framework of the aryl ring, thereby minimizing 1,3-allylic strain. Moreover, orthogonal multipolar C-F•••C=O interactions have been identified in a phathalimide derivative. It is envisaged that this programmed vicinal difluorination enabled by a hypervalent iodine species will find application in functional molecule design in a broader sense.