Cheng Zhong

We report a regiodivergent strategy for the catalytic asymmetric synthesis of enantioenriched spirocyclic γ- and δ-lactams from a single cyclic alkyne-tethered β-ketoamide precursor. Critically, simply switching the catalyst system between Cu(I)/Pyrabox and Ni(II)/Box enables precise toggling of the cyclization between 5-exo-dig and 6-endo-dig modes, allowing direct and highly stereoselective access to either γ-lactam or δ-lactam spirocycles, each bearing a challenging quaternary spiro-stereocenter. The method exhibits broad functional group compatibility and allows for gram-scale synthesis. Mechanistic experiments and DFT calculations reveal that regioselectivity arises from the mode of metal coordination or the joint regulation by metal and ligand, whereas stereocontrol is governed by steric hindrance between the ligand and the substrate. This practical and atom-economical approach provides a powerful platform for the divergent synthesis of privileged spirocyclic pharmacophores.

In this work, a series of D–A conjugated polymer donors (namely PBDT-BBTH, PBDT-BBTF and PBDT-BBTCl) was designed based on the benzobisthiazole (BBT) unit in the 4,8-connection mode with the benzodithiophene (BDT) unit linked by the thiophene π-bridge. At the same time, an α-alkyl-thiophene ring with different β-atoms (H, F and Cl) was introduced at 2,6-positions of the BBT unit as a side-chain to extend the conjugation and regulate the energy levels. In 4,8-connection mode, the aromatic fused-thiazole ring of the BBT unit can stabilize the quinoid configuration of the main chain to strengthen the intramolecular charge transfer (ICT) and improve the π-electron delocalization of the conjugated backbone. The DFT calculations indicate that there exists the N⋯S noncovalent interaction between the BBT unit and the adjacent thiophene π-bridge that can lock the main-chain conformation to enhance the rigidity of the conjugated backbone. Thus, these polymers exhibit strong absorption in the range of 300–650 nm, which is favorable for light-harvesting to improve the short-circuit current density (J_SC) of the organic solar cells (OSCs). In addition, the introduction of a strongly electronegative F or Cl atom at the β-position of the α-alkyl-thiophene side-chain can reduce the HOMO energy level, which is beneficial for the enhancement of the open-circuit voltage (V_OC). Finally, the optimized OSC devices based on these polymers with an L8-BO acceptor exhibit good J_SC over 22 mA cm⁻², and the devices based on PBDT-BBTF and PBDT-BBTCl show higher V_OC than the device based on PBDT-BBTH. Among these polymers, the PBDT-BBTF-based device achieves more balanced parameters (J_SC = 23.43 mA cm⁻², V_OC = 0.831 V, and FF = 73.36%) to lead to the best PCE of 14.27%.

Contrary to previous results, a unique anti-correlation effect of the alkyl chain size on the photovoltaic performance of acceptors was observed. For a centrally-extended acceptor, replacing linear alkyl chains (n-undecyl for CH-BBQ) on the thienothiophene unit with branched ones (2-butyloctyl for CH-BO) leads to a plunge in the power conversion efficiency of organic solar cells (18.12% vs. 11.34% for binary devices), while the largely shortened ones (n-heptyl for CH-HP) bring a surge in performance (18.74%/19.44% for binary/ternary devices). Compared with CH-BO, the more compact intermolecular packing of CH-HP facilitates carrier transport. The characterization of organic field effect transistors and carrier dynamics also echoes the above results. Molecular dynamics simulations indicate that the encounter of the branched alkyl chains and the extended central core hinders the effective interfacial interaction of polymer donors and acceptors, thus deteriorating the device performance. This work suggests that the conventional strategy for alkyl chain engineering of Y-series acceptors might need to be reconsidered in other molecular systems.

Realizing high luminescence dissymmetry factor (g) in circularly polarized luminescence (CPL) materials remains a big challenge, which necessitates understanding systematically how their molecular structure controls the CPL. Here we investigate representative organic chiral emitters with different transition density distributions and reveal the pivotal role of transition density in CPL. We rationalize that to obtain large g-factors, two conditions should be simultaneously satisfied: (i) the transition density for the S₁ (or T₁)-to-S₀ emission must be delocalized over the entire chromophore; and (ii) the chromophore inter-segment twisting must be restricted and tuned to an optimal value (∼50°). Our findings offer molecular-level insights into the CPL of organic emitters, with potential applications in the design of chiroptical materials and systems with strong CPL effects.

A simple oligothiophene donor (Tz6T) was developed for organic solar cells. The devices with Tz6T achieved power conversion efficiencies (PCEs) of up to ca. 15.4%, representing one of the crest values achieved by oligothiophene donors.

A new D–A emitter with HLCT and AIE characteristics has been designed based on BTT acceptor and TPA donor, and non-doped and doped solution-processed devices show deep-red emission.

Local inhomogeneities in lipid composition play a crucial role in the regulation of signal transduction and membrane traffic. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids. Nevertheless, most evidence for microdomains in cells remains indirect, and the nature of membrane inhomogeneities has been difficult to characterize. We used a new push–pull pyrene probe and fluorescence lifetime imaging microscopy (FLIM) combined with all-atom multiscale molecular dynamics simulations to provide a detailed view on the interaction between phospholipids and phytosterol and the effect of modulating cellular phytosterols on membrane-associated microdomains and phase separation formation. Our understanding of the organization principles of biomembranes is limited mainly by the challenge to measure distributions and interactions of lipids and proteins within the complex environment of living cells. Comparing phospholipids/phytosterol compositions typical of liquid-disordered (Ld) and liquid-ordered (Lo) domains, we furthermore show that phytosterols play crucial roles in membrane homeostasis. The simulation work highlights how state-of-the-art modeling alleviates some of the prior concerns and how unrefuted discoveries can be made through a computational microscope. Altogether, our results support the role of phytosterols in the lateral structuring of the PM of plant cells and suggest that they are key compounds for the formation of plant PM microdomains and the lipid-ordered phase.

The structural modulation of phenolic D–A type fluorophores and a NIR fluorescent probe for cysteine imaging in vitro and in vivo.