Ion-transfer voltammetry at the liquid-liquid interface is a powerful tool for the label-free detection of non-redox-active ionic species and for the mechanistic investigation of ion and electron transfer processes at liquid-liquid interfaces. Apart from analytical applications, these interfacial phenomena are highly relevant to developing next-generation electrocatalytic, photoelectrocatalytic, and energy-storage systems. However, conventional ITIES cells (interface between two immiscible electrolyte solutions) require custom fabrication and large volumes of often toxic organic solvents (5–10 mL). Considerable volume of the organic phase limits their applicability to investigate scarce, expensive, or newly synthesized molecules. Although existing miniaturized formats reduce solvent consumption, they introduce asymmetric diffusion profiles that complicate data analysis and require greater operator skill. Here, we introduce a miniaturized electrochemical cell that maintains a macroscopic liquid-liquid interface with symmetric diffusion from both phases. This design enables direct comparison with established ITIES studies while drastically reducing reagent consumption. The device is constructed from readily available laboratory materials—a glass spectrophotometric cuvette and a Pasteur pipette—and requires only 150–200 µL of each phase. Its transparent design enables real-time visualization of interfacial processes, including deposit formation, bubble evolution, and microemulsion development. The compact configuration is fully compatible with spectroelectrochemical measurements. We demonstrate the cell's utility through spectroelectrochemical characterization of electron-transfer reactions involving ferrocene/hexacyanoferrate and a newly synthesized organoboron ferrocene system.

This study explores the effect of the carbonyl group on the photophysical, electrochemical, and thermal properties of a series of 5,10-diheterotruxenes and their carbonyl-containing analogues (truxenones). Spectroscopic analysis revealed that heteroatoms significantly influence the optical properties of the molecules, while the carbonyl group causes pronounced bathochromic shifts (up to the near-infrared region (NIR)) and fluorescence quenching. Electrochemical studies demonstrated that carbonyl introduction stabilizes the electronic structure, enabling reversible reduction and altering oxidation behavior, with NN(CO) emerging as a promising semiconductor. Moreover, 5,10-diheterotruxen-15-ones proved to be very efficient 1O2 sensitizers.

Three benzindolo-benzochalcogenazolo-based boron difluoride complexes (bI-NNB-bCh) incorporating benzoxazole, benzothiazole, and benzoselenazole acceptor units were synthesized and studied as emissive materials for organic light-emitting diodes (OLEDs). The compounds exhibit favorable electrochemical and photophysical properties, enabling their integration into vacuum-deposited OLEDs. Devices employing a conventional OLED host produce yellow-green electroluminescence with external quantum efficiencies (EQEmax) of 3.80%. Among the investigated emitters, the benzothiazole derivative delivers the best device performance, consistently with its higher photoluminescence quantum yield of 96% in the polymeric matrix. Replacing an OLED host exhibiting thermally activated delayed fluorescence results in near-white electroluminescence, demonstrating the critical influence of host-guest interactions and excited-state environments on emission characteristics. Under these conditions, close to 25% enhancement of EQEmax was achieved for the benzothiazole-based devices emitting near-white electroluminescence with color coordinates of (0.38; 0.42). These results highlight heteroaromatic acceptor engineering within the bI-NNB-bCh framework as an effective strategy for tuning photophysical properties and OLED performance.

We report striking photophysical behaviour of Au25(PET)18 (PET = 2-phenylethanethiol) nanoclusters in both anionic and neutral forms. Using broad spectral coverage and tuneable excitation, steady-state, and time-resolved measurements reveal low-energy absorption and emission features, weak photoluminescence, and multiexponential decay dynamics. Notably, the neutral species shows excitation-wavelength-dependent emissions and a pronounced mismatch between excitation and absorption spectra, violating Kasha's and Vavilov's rules. These results point towards complex excited-state behaviour of these systems and the crucial role of instrumentation design in their accurate characterisation.

Sepantronium bromide, which shows a broad spectrum of anticancer action, is allegedly chemically unstable. This instability might significantly limit the final antineoplastic efficacy of the drug. Here, we report our studies on these chemical stability issues under different chemical environments using advanced spectroscopies. With UV-Vis spectroscopy, we observed a degradation product which absorbs around 450 nm. The degradation accelerated strongly at alkaline pH (>8.5) and in the presence of a buffer, particularly PBS. We performed NMR and stimulated Raman studies to identify the degradation product and analysed the degradation kinetics. With both methods, we observed H → D isotope exchange at the methyl group linked to the imidazole group of YM155, after dissolving YM155 in D2O. The exchange was similarly both alkaline- and buffer-catalysed. We were unable to identify the 450 nm-absorbing product of the degradation neither by NMR nor stimulated Raman, yet our studies pointed at imidazole-linked methyl as being associated with the YM155 degradation. The alkaline degradation of YM155 could be related to its mechanism of action - binding to DNA in mitochondria with pH values above 8.

A new series of donor-acceptor benzochalcogenazole-based N,O-coordinated boron difluoride complexes (1a,b-3a,b) has been synthesized for applications in organic solid-state lasers and light-emitting diodes. The effect of the chalcogen atom (O, S, Se) in the benzochalcogenazole core on the photophysical properties was systematically studied. While the compounds show negligible fluorescence in solution, they exhibit pronounced aggregation-induced emission and strong solid-state luminescence, with photoluminescence quantum yields up to 48% in the crystalline state and 56% in poly(methyl methacrylate) films. Benzoxazole- and benzothiazole-based derivatives display amplified spontaneous emission with thresholds as low as 10.1 μJ/cm2, which enables to perform efficient organic solid-state lasers. Meanwhile, benzothiazole- and benzoselenazole-containing compounds exhibit both prompt and efficient delayed fluorescence. OLED devices incorporating these emitters demonstrated efficient energy conversion and bright electroluminescence. Benzothiazole-based complexes 2a and 2b achieved maximum external quantum efficiencies of 9.0% and 16.5%, respectively, with luminance values exceeding 23,000 cd/m2. In contrast, the benzoselenazole analogue 3a, despite a higher delayed fluorescence-to-prompt fluorescence ratio, showed lower device efficiency, highlighting the impact of heteroatom selection on exciton dynamics. These findings establish benzothiazole-containing boron difluoride complexes as promising, thermally stable emitters for high-performance solid-state laser and OLED applications. The results underscore the potential of molecular design and heteroatom engineering to further enhance efficiency and operational stability in organic optoelectronic devices.

We report structural and physicochemical characterization supported by quantum chemical studies of two novel copper(ii) [CuLCl]2[CuCl4] (1) and cobalt(ii) [CoLCl][CoL ' Cl3] (2) cationic-anionic complexes with N-scorpionate type ligand, N,N,N-tris(3,5-dimethylpyrazol-1-ylmethyl)amine (L), where L ' is 1-methylamine-3,5-dimethylpyrazole. The obtained complexes are the first reported examples of cationic-anionic coordination compounds tested for catecholase activity. Interestingly, only copper complex (1) shows catalytic activity in the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC), which turned out to be solvent dependent. Here, experimental UV-vis spectroscopy of 1 shows that essential features of the solid-state spectrum are maintained in DMSO and MeOH solvents. In contrast, the build-up of a new feature around 465 nm for 1 in CH3CN was noted, along with negligible activity. According to quantum chemical calculations, this feature could be attributed to ligand-to-metal excitations within the [CuCl4]2- fragment disturbed by adjacent [CuLCl]+ species. The band shifts to lower energies compared to solid-state measurements as the two charged fragments get closer due to Coulomb interactions. In DMSO, the solvent molecule serves as an inert ligand in a [CuLCl]+ fragment and blocks the catalytic center, disturbing the formation of the [catalyst-substrate] complex and decreasing activity, while in MeOH, the solvent effectively stabilizes [CuCl4]2-via a H-bond network and the free coordination site is accessible, thus allowing a substrate molecule to bind. The critical advantage of the investigated complexes, in the context of their possible catalytic activity, was the fact that their usage would not introduce any unnecessary counterions.

When encountering complex fluorescence decays that deviate from exponentiality, a very appealing approach is to use lifetime or rate constant distributions. These are related by Laplace transform to the sum of exponential functions, stretched exponentials, Becquerel’s decay function, and others. However, the limitations of this approach have not been sufficiently discussed in the literature. In particular, the time-independent probability distributions of the rate constants or decay times are occasionally used to describe bimolecular quenching. We show that in such a case, this mathematical formalism has a clear physical interpretation only when the fluorophore and quencher molecules are immobile, as in the solid state. However, such an interpretation is no longer possible once we consider the motion of fluorophores with respect to quenchers. Therefore, for systems in which the relative motion of fluorophores and quenchers cannot be neglected, it is not appropriate to use the time-independent rate or decay time distributions to describe, fit, or rationalize experimental results on fluorescence decay.

Four donor-acceptor boron difluoride complexes based on the carbazole electron donor and the [1,3,5,2]oxadiazaborinino[3,4-a][1,8]naphthyridine acceptor were designed, synthesized, and systematically spectroscopically investigated in solutions, in dye-doped polymer films, and in the solid states. The dyes exhibit an intense blue to red solid-state emission with photoluminescence quantum yields of up to 59 % in pure dye samples and 86 % in poly(methyl methacrylate) films. All boron complexes show aggregation-induced emission and reversible mechanofluorochromism. The optical properties of these dyes and their solid state luminescence can be tuned by substitution pattern, i. e., the substituents at the naphthyridine unit. Exchange of CH3- for CF3-groups does not only increase the intramolecular charge transfer character, but also provides a crystallization-induced emission enhancement. Four solid-state luminescent donor-acceptor boron difluoride complexes based on the carbazole electron donor and [1,3,5,2]oxadiazaborinino[3,4-a][1,8]naphthyridine acceptor were designed and synthesized. These dyes exhibit aggregation-induced emission and reversible mechanofluorochromism. The incorporation of CF3-groups into naphthyridine unit provide the crystallization-induced emission enhancement of the dyes. image

An approach to analysing time-resolved fluorescence spectra has been developed for dyes with non-parabolic free energy curves of the excited and ground states. It incorporates the description of the solvent relaxation and redistribution/relaxation of intramolecular high-frequency vibrations proceeding in parallel with the pumping. The approach has been applied to simulate spectra of covalently linked perylene-dimethylaniline (PD) in a series of solvents of different polarity. The developed approach combined with the achieved temporal resolution of the modern fluorescence upconversion spectroscopy is shown to provide a possibility to disentangle the relaxation of high-frequency vibrations and the dynamics of the solvent. In this compound the reorganization of both intramolecular vibrations and the solvent strongly affects the absorption and fluorescence spectra so that their influence on spectral dynamics is highly entangled. The comparison of fluorescence spectral dynamics of two dyes, coumarin 153 and PD, shows that the solvation dynamics depend on the fluorophore. The fitting of simulated fluorescence spectral dynamics of PD to the experimental data enables us to determine the solvent relaxation function of hexane. (C) 2022 Elsevier B.V. All rights reserved.

Hypothesis: The coil-to-globule transition is an essential phenomenon in protein and polymer solutions. Late stages of such transitions, >1 ms, have been thoroughly studied. Yet, the initial ones are a matter of speculations. Here, we present the first observation of a sub-nanosecond stage of the coil-to-globule transition of poly (vinyl methyl ether), PVME, in water. Experiments: The detection of an early stage of the coil-to-globule transition has been possible thanks to a novel experimental approach - time-resolved elastic light scattering study, following an ultrafast temperature jump. We identified a molecular process active in the observed stage of the transition with use of broadband dielectric spectroscopy. Findings: In the experiment's time window, from a few ps to around 600 ps, we observed an increase in the light scattering intensity 300-400 ps after the temperature jump that heated the sample above its lower critical solution temperature (LCST). The observed time coincides with the time of segmental relaxation of PVME, determined by broadband dielectric spectroscopy in the temperature range of the LCST of the PVME/water mixture. This coincidence strongly suggests that the observed herein stage of coil-to-globule transition is the rapid formation of local nuclei along the polymer chain. Those nuclei may grow and aggregate in later stages of the process, which are out of our experimental time window. (c) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

We present a quantitative analysis of the deviations introduced by the anisotropy of the fluorescence on the measurement of the quantum yield of emission. Errors of up to 40% can be encountered depending on the characteristics of both sample and apparatus. Additionally, we have analyzed the effect of anisotropy on the study of fluorescence quenching in Stern-Volmer experiments, and on the reconstruction of time-resolved emission spectra. We conclude that the use of polarizers is recommended provided they are well characterized.

Several aspects contributing to the temporal broadening in the measurement of ultrafast fluorescence by means of up-conversion wave mixing are presented: the characteristics of the sample, those of the collection optics, and the wave mixing with the gate pulse in a non-linear crystal. It is concluded that these contributions are emission wavelength dependent and can be as important as the pulse durations in determining the instrument response function in this technique.

This work aims to describe anisotropy effects on chemical reactions imposed by the structure of liquid crystals. Photo-induced intermolecular electron transfer is studied by means of fluorescence quenching. The charge shift and charge separation reactions are investigated in two different chemical systems. Steady state and time resolved measurements are performed to track the reaction kinetics. In order to extract the electron transfer parameters which are independent of the solvent, the reactions are also conducted in isotropic media at different temperatures and viscosities. A set of diffusion-reaction models with different levels of anisotropy has been developed as well as a numerical method to solve the corresponding partial differential equations. Only the model which introduces anisotropic diffusion and reactivity gives physically meaningful values for all parameters entering the reactivity. It is therefore shown how to adapt diffusion-reaction models able to accommodate any sort of reactivity to complex environments.

Photochemical electron transfer between freely diffusing molecules has been studied extensively. Here, we try to elucidate how much these works have contributed to the understanding of electron transfer. To this end, we have revisited the work performed in the experimental and theoretical areas of concern from the beginning of the 20th century up to the present day. We present a critical look at the major contributions and compile the current picture of a variety of phenomena around electron transfer in solution. This is based on two main developments, besides the theory of Marcus: encounter theories of diffusion and laser techniques in time-resolved spectroscopy.

A general analytical expression for the transient fluorescence spectrum is derived. The formation of a wave packet in the excited state of a fluorophore is described, assuming that the pump pulse has a Gaussian time-profile. The expression explicitly connects the relaxation characteristics of the medium with the spectral dynamics of a fluorophore. Fitting the expression to experimental spectral dynamics allows obtaining the solvent relaxation function. So far this approach was applicable for the analysis of experimental data when the pump pulse does not populate excited sublevels of intramolecular high-frequency vibrational modes. Here, the approach is generalized to include vibrational relaxation in the excited electronic state. In this case, fitting to the experimental spectral dynamics provides reliable information not only on the solvent relaxation, but also on the relaxation time constants of intramolecular high-frequency vibrational modes. This approach is applied to the excited state dynamics of coumarin 153 in multiple solvents, obtained from broadband fluorescence upconversion spectroscopy.

A set of substituted 9,10-dicyanoanthracenes (DCA) has been synthesized, their photophysicaland electrochemical properties in liquid solution have been characterized and supplemented byhigh level ab initio quantum chemical calculations. Three different methoxy-group-containing substituents have been linked to the DCA core in a symmetric and asymmetric fashion to produce sixdifferent species with strong quadrupole and dipole moments, respectively. The major differencebetween the symmetrically and asymmetrically substituted species are the enhanced two-photonabsorption intensities of the former. In most of the cases studied, the molecules show reasonably large optical transition probabilities. The fluorescence brightness of these substances makesthem interesting objects for two-photon absorption applications. Additionally, all molecules can beboth easily reduced and oxidized electrochemically and are therefore suitable for optoelectronicapplications.

Disentangling overlapping spectral signatures with time-dependent shape is performed using additional information contained in ultrafast transient absorption data, without applying any assumption on the underlying kinetics.

A new hydroxybenzofluorenone has been designed and synthesised in order to investigate the origin of excited state intramolecular proton transfer reactions in this family of compounds. 10-Hydroxy-11H-benzo [b]fluoren-11-one (10-HHBF) does not show dual fluorescence in contrast to its well known analogue 1-hydroxy-11H-benzo [b]fluoren-11-one (1-HHBF). It is suggested that in 10-HHBF ESIPT is not occurring. The origin of the difference between these isomers is likely to be found in the increased donor-acceptor distance in 10-HHBF and in the lower stability of its excited state tautomer. This streses the large impact in the photophysics of this class of materials of subtle structural changes which must be taken into account for the desingn of single-molecule white light emitters.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.