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Charged molecules play essential roles in many natural and artificial functional processes, ranging from photosynthesis to photovoltaics to chemical reactions and more. It is often difficult to identify the optical dynamic properties of relevant redox species because they cannot be easily prepared, their spectra overlap, or they evolve on a femtosecond timescale. Here, we address these challenges by combining spectroelectrochemistry, ultrafast transient absorption spectroscopy, and suitable data analysis. We illustrate the method with the various redox species of a cyclophane composed of two perylene bisimide subunits. While singular-value decomposition is a well-established tool in the analysis of time-dependent spectra of a single molecular species, we here use it additionally to separate transient maps of individual redox species. This is relevant because at any specific applied electrochemical potential, several redox species coexist in the ensemble, and our procedure allows disentangling their spectroscopic response. In the second step, global analysis is then employed to retrieve the excited-state lifetimes and decay-associated difference spectra. Our approach is generally suitable for unraveling ultrafast dynamics in materials featuring charge-transfer processes. [ABSTRACT FROM AUTHOR]

Harvesting triplet excitons of heavy atom‐free purely organic chromophores under aerated conditions is challenging due to the quenching of long‐lived triplet states by molecular oxygen and vibrational dissipation. Herein, we show a supramolecular approach of triplet harvesting via mitigating quenching pathways of a triplet harvester. Specifically, we used a host–guest system based on 2,3 : 6,7‐naphthalene bis(dicarboximide)‐derived cyclophane (NBICy) and carbazole derivative (EtCz). Complexation studies and single‐crystal X‐ray analysis showed the formation of a rigid host–guest complex (K≈104 M−1 in CCl4), resulting in triplet‐exciton stabilization under aerated conditions via mitigating vibrational interference and oxygen quenching. Photophysical studies elucidate the delayed fluorescence emission from the charge‐transfer state (1CT) with a quantum yield (QY) of 6–8 % under ambient conditions which increased up to 36 % in an inert atmosphere. [ABSTRACT FROM AUTHOR]

Near‐Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin–orbit coupling and a low energy gap leading to fast non‐radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low‐lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X‐ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π‐surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid‐state sample drop‐casted from a preformed complex in solution. Theoretical calculations reveal a non‐zero spin–orbit coupling between isoenergetic S1 and T3 of π‐stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy‐atom‐induced spin–orbit coupling along with rigidification and protection from oxygen in the solid‐state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1. [ABSTRACT FROM AUTHOR]

The dynamic nature of calamitic liquid crystals is exploited to perform isothermal phase transitions driven by dynamic covalent chemistry. For this purpose, nematic (N) arrays based on aldehyde 1 were treated with different amines (A–E) in an on‐surface process, which resulted in different isothermal phase transitions. These phase transformations were caused by in situ imination reactions and are dependent on the nature of the added amine. Transitions from the N to crystal (1A, 1E), isotropic (1B), and smectic (Sm) (1C, 1D) phases were achieved, while the resulting materials feature thermotropic liquid crystal behavior. A sequential transformation from the N 1 to the Sm 1C and then to the N 1B was achieved by coupling an imination to a transimination processes and adjusting the temperature. All of these processes were well characterized by microscopic, spectroscopic, and X‐ray techniques, unlocking not only the constitutional but also the structural aspects of the phase transitions. This work provides new insights into designing constitutionally and structurally adaptable liquid crystal systems, paving the way toward the conception of programable evolutive pathways and adaptive materials. [ABSTRACT FROM AUTHOR]

Highly anisotropic thin films of H-type coupled dipolar merocyanines with large dichroic ratios of over 50 were deposited by solution shearing. These layers were incorporated into simultaneously color- and polarization-selective organic photodiodes. Using a transparent non-fullerene acceptor, polarization-sensitive planar-heterojunction devices with an average visible transmittance of 93% were obtained. [ABSTRACT FROM AUTHOR]

Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface‐to‐volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade‐off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n‐type single crystal. Step edges, serving as adsorption sites with electron‐deficient properties, are well‐defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap‐like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two‐terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi‐log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing. [ABSTRACT FROM AUTHOR]