Band 98, Heft 1 - Special Issue: International Conference on Physical Organic Chemistry; Guest Editors: Lei Jiao and Sanzhong Luo

The correct use of IUPAC terminology can facilitate clarity in scientific publications, litigation, and education. This document summarizes IUPAC’s recommendations for polymer terminology. In the version attached in the Supplementary Information, hyperlinks lead to the original source material, and screen-tips give the definitions as published by IUPAC.

Self-oscillating gels driven by the Belousov-Zhabotinsky reaction represent a novel class of smart materials that exhibit autonomous, reversible, and periodic changes in color and size without the need for external stimuli. Currently, most such gels are based on catalytically active ruthenium complexes, which are not only expensive but also light-sensitive, potentially limiting their practical application. Therefore, the development of self-oscillating gels based on non-ruthenium catalysts is an important task, since there is a need for inexpensive and accessible chemomechanical materials for industrial use. This review presents and summarizes the advancements made in self-oscillating gels based on Fe, Co, and Ce catalysts. Furthermore, it discusses the opportunities, challenges, and future directions in this emerging field.

Molecular topology fundamentally influences self-assembly, molecular recognition, and dynamic behavior in chemical systems. Among topologically nontrivial architectures, Möbius molecules – defined by a non-orientable, fully conjugated cyclic backbone with an odd linking number (Lk) – represent a unique class of π-conjugated macrocycles distinct from geometrically twisted analogues. Their one-sided surface and topological singularity confer exceptional properties, including intrinsic chirality, delocalized electronic pathways, and unconventional charge transport characteristics, positioning them as promising platforms for applications in optoelectronics, chiral sensing, and molecular electronics. Despite significant synthetic challenges arising from ring strain and conformational instability, recent advances in dynamic covalent chemistry, metal-templated cyclization, and heteroatom incorporation have enabled the construction of stable Möbius nanobelts and heterocyclic macrocycles with tunable redox and photophysical properties. Beyond discrete molecules, Möbius topology has also been extended to supramolecular assemblies and interlocked systems, broadening the functional scope of these structures. This review surveys recent progress in the design, synthesis, and functional exploration of Möbius systems, highlighting the critical role of topology in shaping their structure–property relationships and their emerging impact on supramolecular chemistry and molecular materials science.

Precise snake venom identification is the prerequisite for clinical treatment, production of antiserum, basic research, and other applications. Unfortunately, it is still a challenging task which mainly originates from their extraordinary complicated protein composition. Differential sensing strategy was applied benefiting from its advantage in discrimination of complex mixtures. Herein, A dual-mode supramolecular fluorescent sensor array based on the heteromultivalent sensing strategy was developed. The heteromultivalent macrocyclic coassemblies with strong and pan-selective binding to proteins were employed to construct sensor units. Fluorescence intensity and anisotropy signals were integrated, which were expected to show multidimensional information of proteins, such as surface groups, protein structures, and molecular weights. Finally, a supramolecular sensor array with the ability of facile, rapid and general species-specific identification and taxonomic classification for snake venom was constructed. The sensor array also demonstrated its advantage in semiquantitative analysis and multi-level identification, suggesting its great potential for practical use.

The development of robust machine learning models to assist the prediction and optimization of homogeneously catalyzed reactions has attracted wide interests. In this work, we propose a workflow to estimate the linear to branched ratio of the products in hydroformylation reactions using a stacking ensemble method that integrates Random Forest, eXtreme Gradient Boosting, and Light Gradient Boosting Machine algorithms, leveraging physicochemically significant features from small-batch experimental data. The stacking model achieves superior performance with R 2 and Root Mean Square Error values of 0.918 and 0.078, respectively. Moreover, the SHapley Additive exPlanations analysis and density functional theory calculations reveal the significant impact of the gap values between the highest occupied molecular orbital and lowest unoccupied molecular orbital of alkenes on the regioselectivity of hydroformylation reactions, indicating that larger gap values tend to result in a higher proportion of the linear products. This study illustrates that the combination of physicochemically significant features and interpretable ensemble models can serve as a useful strategy for predicting regioselectivity in homogeneously catalyzed reactions.

Many organic reaction mechanisms are complex and may involve both multiple steps in series and multiple pathways in parallel. Consequently, for many reactions occurring in condensed media (including enzyme-catalyzed reactions) there is no single rate-determining step associated with a unique transition state (TS): in general, any ‘transition-state structure’ derived from experimental kinetics investigations of a complex mechanism is an average corresponding to a virtual TS. Computational simulation is now capable of yielding valuable insight, complementary to experiment, for minima and saddle points on potential-energy surfaces, corresponding to intermediates and TSs on Gibbs-energy surfaces for complex reactions with multiple TSs in parallel or in series. For a reaction with multiple steps in series, the apparent Gibbs energy of activation (corresponding with a virtual TS) is a sum of terms, one for each contributing real TS j ; the kinetic significance w j of each is given by exp(Δ ‡ G j /RT)/exp(Δ ‡ G app /RT). An analogous expression applies to the kinetics of reaction steps in parallel, except that each Gibbs energy is preceded by a minus sign, and the contribution w i of each real TS to Δ ‡ G app is its Boltzmann weighting, and the mole fraction of the lowest-energy reactant conformer must be factored in. Examples of both types of reaction are discussed to illustrate the concept of the virtual TS.

Water-soluble flexible organic frameworks (FOFs) can be constructed from multi-topic cationic, anionic or neutral, hydrophilic components through the quantitative formation of dynamic hydrazone or disulfide bond. FOFs have been revealed to possess intrinsic porosity, hydrophobic interior, and controllable nano-sizes. They function well as homogeneous nano-sponges for including proteins, DNA, residual drugs, such as neuromuscular blocking agents and heparins, and endotoxin. Their nano-sizes endow the frameworks with good ability for intracellular delivery of the included proteins and DNA and for the design of self-delivering prodrugs, while efficient inclusion of residual drugs can be utilized to develop FOF antidotes for inactivating the residual drugs. This review summarizes the design, preparations, characterizations and biofunctions of this family of dynamic covalent polymers.

Diazoalkanes are ambiphilic molecules that may react with electrophiles at carbon to give diazonium ions, with nucleophiles at nitrogen to yield azo compounds, or with dipolarophiles to produce pyrazolines. By studying the kinetics of the reactions of methyl diazoacetate and dimethyl diazomalonate with benzhydrylium ions (Ar 2 CH + ) of known electrophilicity E , we determined their one-bond nucleophilicity parameters N and s N using the equation lg k 2 (20 °C) =  s N ( N  +  E ) (eq. (1)). Similarly, the electrophilicity parameters E of these diazoesters were obtained by measuring the rate constants of their reactions with one-bond nucleophiles of known N and s N . These reactivity parameters enable the calculation of rate constants for 1,3-dipolar cycloadditions with dipolarophiles, which proceed stepwise with rate-determining formation of zwitterionic intermediates. Concerted cycloadditions proceed faster than calculated by eq. (1), and the difference between the observed rate constants (Δ G ‡ exptl ) and those calculated by eq. (1) (Δ G ‡ eq. 1 ) gives the energy of concert (Δ G ‡ concert  = Δ G ‡ eq. 1  − Δ G ‡ exptl ). Contrary to earlier reports, cycloadditions of methyl diazoacetate and dimethyl diazomalonate with enamines proceed stepwise through initial azo couplings. This involves enamine attack at the π* (N=N) orbital of the diazoalkane, oriented perpendicularly to the commonly considered 3-center 4-electron π-system. Since this orbital was previously ignored, the common FMO analysis of the reactions of 1,3-dipoles of the propargyl anion type requires revision. A new ordering system for 1,3-dipolar cycloadditions is proposed.

4-Amino-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical was linked to perylene-3,4:9,10-bis(dicarboximide) (PBI) at varying distances and orientations. PBI-TEMPO dyads with the radical linked at the bay-position show a charge transfer absorption band in the UV−vis absorption spectra. With increasing solvent polarity, a fluorescence quenching is observed for these dyads, whereas for a derivative with TEMPO attached at the imide-position, such polarity dependency for fluorescence spectra was not observed. Steady state and femtosecond/nanosecond time-resolved optical spectroscopy confirmed the occurrence of radical-enhanced intersystem crossing (REISC. k ISC  = (23 ps) −1  − (0.5 ns) −1 ). The lifetime of the 3* PBI state ( τ T  = 1.0–7.6 μs) depends on the distance and orientations between TEMPO and PBI units. The results indicate that stronger electron spin–spin dipolar interaction ( v dd ) between the radical and the chromophore improve REISC efficiency. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy demonstrates different electron exchange interactions ( J TR ) in the dyads, varying from ferromagnetic interaction corresponding to strong exchange regime to weak antiferromagnetic exchange interaction with increasing the distance between PBI and TEMPO units. Transient-nutation experiments further clarify the TREPR signals. DFT calculations indicate that changes in the dyad structure alter the exchange coupling from ferromagnetic ( J TR  = 0.47 cm −1 ) to antiferromagnetic ( J TR  = −0.03 cm −1 and −0.01 cm −1 ).

Computer simulations of carbohydrates pose a significant challenge due to their heterogeneous chemical structure, high conformational variability, inaccuracies in interaction potentials, and computational inefficiency, which scales particularly unfavorably with chain length compared to other biopolymers. In this work, we present a coarse-grained model designed for Monte Carlo simulations of single polysaccharide chains of realistic lengths (hundreds of monomers or more). The model specifically accounts for the structural features of natural polysaccharides, which are typically built from disaccharide building blocks, and for conformational variability arising from rotations around glycosidic linkages. By extrapolating local conformational properties, thermodynamically correct configuration ensembles are generated, and high computational efficiency is achieved through rapid decorrelation of independent degrees of freedom. As an illustration of the model’s capabilities, we present a set of simulations of keratan, a natural biopolysaccharide belonging to the glycosaminoglycan family. The results indicate that sulfation has a limited impact on chain conformation. Instead, chain stiffness is primarily influenced by syn-exo ↔ anti -ψ conformational transitions in β(1 → 4) glycosidic linkages. The persistence length varies between 6 and 8 nm depending on the degree of sulfation. Moreover, for chain lengths most commonly found in nature, a linear relationship is observed between the number of monomeric units and both the radius of gyration and the end-to-end distance. Finally, we present and discuss the strategy for accounting for ionic-strength-driven alterations of the charged polysaccharide chain, which, when applied to the current case, demonstrate that, under physiological conditions, the long-range electrostatic interactions within the keratan chain can be neglected.