Abstract Photoinduced symmetry-breaking charge separation (SB-CS) is a fundamental process in molecular photophysics that underpins energy and charge transport in reaction centers and organic, supramolecular, and hybrid materials. Despite extensive investigations across diverse systems, SB-CS is often described in system-specific terms, obscuring the underlying unifying principles. In this Review, we establish a coherent framework demonstrating that SB-CS can be understood within a multidimensional parameter space defined by electronic coupling, energetic driving force, and nuclear reorganization. We critically analyze how the interplay between locally excited and charge-transfer states governs charge separation and recombination dynamics, highlighting the existence of an optimal intermediate coupling regime that enables efficient symmetry-breaking while suppressing nonproductive decay pathways. By integrating insights from solution, solid-state, and single-molecule measurements, we show that environmental fluctuations and structural heterogeneity play a central role in driving charge localization rather than merely acting as spectators or perturbations. Importantly, we distinguish universal physical principles from system-specific manifestations, allowing the formulation of transferable design rules for achieving efficient and long-lived charge-separated states. Finally, we outline emerging directions toward predictive, data-driven models that link molecular structure to SB-CS dynamics, providing a foundation for the rational design of next-generation optoelectronic and energy-conversion materials.
Abstract Water and aqueous electrolytes at surfaces, interfaces, and in confinement behave differently from the bulk, yet linear spectroscopy rarely combines the chemical specificity, surface selectivity, and temporal resolution needed to resolve electric double-layer formation, specific-ion adsorption, and hydration at interfaces and under nanoconfinement. This review assesses how ultrafast nonlinear vibrational spectroscopy, comprising two-dimensional infrared spectroscopy, vibrational sum-frequency generation (SFG), and time-resolved SFG, probes the hydrogen-bond network and the dynamics of interfacial water and electrolytes on femtosecond-to-picosecond timescales. We first establish vibrational benchmarks for bulk water and simple electrolytes, then treat soft aqueous boundaries, including air–water, hydrophobic and hydrophilic, lipid, surfactant, and nucleic acid interfaces. We next examine solid–liquid and electrochemical systems, spanning metal oxides, minerals, and field-induced effects, before turning to water and proton dynamics in nanoconfined geometries and complex architectures. Throughout, experimental results are set against theoretical and computational frameworks, from polarizable force fields to machine-learning potentials. Our aim is to identify which molecular-level features of interfacial water are now firmly established, where the prevailing mean-field description of the electric double layer breaks down, and which experiments would resolve the outstanding discrepancies.
Abstract Strain-release cycloadditions have emerged as powerful reactions for converting distorted ring systems into complex and otherwise hardly attainable organic molecular architectures. This Review encompasses the fundamentals of strain, its role in governing cycloaddition pathways, and offers a systematic examination of strained carbocycles and heterocycles, from bicyclo[1.1.1]butanes and 1-azabicyclo[1.1.1]butanes, housanes and aza-housanes, 2H-azirines and aziridines, azetidines, cyclopropanes, cyclobutanes, oxiranes, oxetanes, and strained alkynes and alkenes. Across these motifs, the general principles that dictate reactivity, the breadth of known cycloadditions and activation strategies, from Brønsted and Lewis acid catalysis to transition-metal activation, photocatalysis, and double strain-release mechanisms, are highlighted. Key opportunities, current limitations, and future directions are outlined.
Abstract The interfacial electron-transfer process acts as a pivotal kinetic determinant of electrochemiluminescence (ECL) efficiency, governing the generation of excited-state emitters and thus dictating the intensity and stability of ECL signals. Currently, harnessing diverse nanomaterials has driven significant advances in the development of novel ECL luminophores and the activation of coreactants. However, most of these luminophores exhibit low ECL efficiency in aqueous media, and the intrinsic reaction and activation mechanisms remain ambiguous because of their complex structures and compositions. Notably, tuning electron-transfer pathways at the molecular/atomic level can not only enable efficient signal amplification but also facilitate the tracking of reaction pathways, thereby providing deeper insights into the fundamental mechanisms underlying ECL processes. This Review comprehensively summarizes advances during the past five years in tuning interfacial electron transfer to enhance ECL. Furthermore, we highlight progress in electron-transfer-mediated signal amplification strategies for highly sensitive ECL biosensing and bioimaging applications. Finally, we propose and discuss the challenges and perspectives associated with improving the ECL efficiency through the modulation of electron transfer processes. Precise regulation of interfacial electron transfer holds substantial promise for advancing ECL theories, clarifying reaction mechanisms, and expanding the scope of ECL-based bioanalytical applications.
