Conformational, Host, and Vibrational Effects Giving Rise to Dynamic TADF Behavior in the Through-Space Charge Transfer, Triptycene Bridged Acridine-Triazine Donor Acceptor TADF Molecule

We present a joint experimental and theoretical study of the through-space charge transfer (CT) TADF molecule TpAT-tFFO. The measured fluorescence has a singular Gaussian line shape but two decay components, coming from two distinct molecular CT conformers, energetically only 20 meV apart. We determined the intersystem crossing rate (1 × 10⁷ s^-1) to be 1 order of magnitude faster than radiative decay, and prompt emission (PF) is therefore quenched within 30 ns, leaving delayed fluorescence (DF) observable from 30 ns onward as the measured reverse intersystem crossing (rISC) rate is >1 × 10⁶ s^-1, yielding a DF/PF ratio >98%. Time-resolved emission spectra measured between 30 ns and 900 ms in films show no change in the spectral band shape, but between 50 and 400 ms, we observe a ca. 65 meV red shift of the emission, ascribed to the DF to phosphorescence transition, with the phosphorescence (lifetime >1 s) emanating from the lowest ³CT state. A host-independent thermal activation energy of 16 meV is found, indicating that small-amplitude vibrational motions (∼140 cm^-1) of the donor with respect to the acceptor dominate rISC. TpAT-tFFO photophysics is dynamic, and these vibrational motions drive the molecule between maximal rISC rate and high radiative decay configurations so that the molecule can be thought to be "self-optimizing" for the best TADF performance.

Impact of a delayed presentation to the emergency department for acute renal colic on biochemical and clinical outcomes

INTRODUCTION AND OBJECTIVE

To verify the impact of delay on biochemical and clinical outcomes for patients presenting to the emergency department (ED) with acute renal colic.

MATERIALS AND METHODS

Data were retrospectively collected from three institutions of two European countries between 01 January and 30 April 2020. Patients who presented to the ED with unilateral or bilateral renal colic caused by urolithiasis confirmed by imaging tests during the study period were included. A presentation after 24 h since the onset of symptoms was considered a delay. Patients presenting before 24 h from the symptom onset were included in Group A, while the patients presenting after 24 h in Group B. Clinical and biochemical parameters and management were compared.

RESULTS

A total of 397 patients who presented to ED with confirmed urolithiasis were analyzed (Group A, n = 199; Group B, n = 198. The median (IQR) delay in presentation was 2 days (1,5-4). At presentation, no statistically significant differences were found amongst the two groups of patients regarding presenting symptoms such as fever and flank pain, and the median serum levels of creatinine, C reactive protein and white blood cells. No differences were found in terms of conservative or operative management.

CONCLUSION

Delay in consultation >24 h is not associated with worsening biochemical parameters and clinical outcomes. Most patients with acute loin pain do not necessarily need urgent attendance to the ED and may be managed in the outpatients.

Intersystem crossing processes in the 2CzPN emitter: a DFT/MRCI study including vibrational spin-orbit interactions

Multireference quantum chemical calculations were performed in order to investigate the (reverse) intersystem crossing ((R)ISC) mechanisms of 4,5-di(9H-carbazol-9-yl)-phthalonitrile (2CzPN). A combination of density funcional theory (DFT) and multireference configuration interaction methods (MRCI) was used. The excellent agreement of the computed absorption spectrum with available experimental absorption spectra lends confidence to the chosen computational protocol. Vertically, two triplet excited states (T₁ and T₂) are found below the S₁ state. At the excited state minima, the calculated adiabatic energies locate only the T₁ state below the S₁ state. The enhanced charge transfer (CT) character of the geometrically relaxed excited states causes their mutual (direct) spin-orbit coupling (SOC) interaction to be low. Contributions of vibronic SOC to the (R)ISC probability, evaluated by a Herzberg-Teller-like procedure for a temperature of 300 K, are small but not negligible. For ISC, the S₁→ T₁ channel is the fastest (8 × 10⁶ s^-1), while the S₁→ T₂ channel is found to be thermally activated (9 × 10⁴ s^-1) and less efficient when proceeding from the adiabatic S₁ state. Our calculations also reveal, however, a barrierless S₁→ T₂ ISC pathway near the Franck-Condon region. RISC is found to essentially proceed via the T₁→ S₁ channel, with a rate constant of (3 × 10⁴ s^-1) if our adiabatic singlet-triplet energy gap in vacuum (ΔE_ST = 0.12 eV) is employed. Shifting the potentials to match two experimentally reported singlet-triplet energy gaps in toluene (ΔE_ST = 0.21 and 0.31 eV, respectively) leads to a drastic reduction of the computed rate constant by up to 4 orders of magnitude. The T₂ state is not expected to play a major role in mediating triplet-singlet transitions in 2CzPN unless it is directly populated by hot excitons. No indication for a strong vibronic coupling of the T₂ and T₁ potentials is found, which could help overcome the negative exponential dependence of the RISC rate constant on the magnitude of the energy gap.

Assessment of trends and clinical presentation in the emergency department of patients with renal colic during the COVID-19 pandemic era

Introducción

Nuestra hipótesis es que la pandemia por COVID-19, y el estado de alarma impuesto por los gobiernos, pueden haber retrasado las visitas a urgencias por cólicos nefríticos, debido al miedo a contagiarse en los centros sanitarios. Este atraso en acudir a los servicios de urgencias puede llevar a un empeoramiento clínico y aumentar las complicaciones relacionadas con la enfermedad o el tratamiento recibido.

Material y métodos

Realizamos una revisión retrospectiva de 3 centros hospitalarios en España e Italia. Fueron incluidos pacientes atendidos en el servicio de urgencias por cólico renal (unilateral o bilateral) secundario a litiasis confirmadas en pruebas de imagen durante los 45 días previos y posteriores a la declaración del estado de alarma de cada país. Se recolectaron datos demográficos, síntomas y signos de presentación, análisis de sangre y orina, pruebas de imagen, y manejo terapéutico. El análisis estadístico se realizó entre dos grupos, Grupo A: pacientes que acudieron antes de la declaración del estado de alarma y Grupo B: pacientes que acudieron tras la declaración del estado de alarma.

Resultados

Un total de 397 pacientes que acudieron a urgencias por cólicos nefríticos secundarios a litiasis fueron incluidos en el estudio, 285 (71,8%) en el Grupo A y 112 (28,2%) en el Grupo B (p < 0,001). Un total de 135 (47,4%) en el Grupo A y 63 (56,3%) en el Grupo B (p = 0,11) admitieron haber pospuesto su búsqueda de atención médica urgente. En el momento de la valoración inicial, no se encontraron diferencias entre ambos grupos en los niveles de creatinina sérica, leucocitosis, fiebre, oliguria, dolor, o hidronefrosis. Además, no se observaron diferencias en relación con la estancia media, ingreso en el servicio de urología, o necesidad de tratamientos invasivos.

Conclusión

Nuestros resultados muestran una disminución significativa de atenciones en urgencias por cólicos nefríticos tras la declaración del estado de alarma en España e Italia. A diferencia de otros estudios publicados recientemente, no encontramos diferencias en la estancia media, ingreso al servicio de urología, o necesidad de tratamientos invasivos en pacientes que se presentaron antes y después del estado de alarma.

DFT/MRCI assessment of the excited-state interplay in a coumarin-schiff Mg2+ fluorescent sensor

Fluorescent sensors with selectivity and sensitivity to metal ions are an active field in supramolecular chemistry for biochemical, analytical, and environmental problems. Mg²⁺ is one of the most abundant divalent ions in the cell, and it plays a critical role in many biological processes. Coumarin-based sensors are widely used as desirable fluorophore and binding moieties showing a remarkable sensitivity and fluorometric enhancement for Mg²⁺ . In this work, density functional theory/multireference configuration interaction (DFT/MRCI) calculations were performed in order to understand the sensing behavior of the organic fluorescent sensor 7-hydroxy-4-methyl-8-((2-(pyridin-2-yl)hydrazono)methyl)-2H-chromen-2-one (PyHC) in ethanol to solvated Mg²⁺ ions. The computed optical properties reproduce well-reported experimental data. Our results suggest that after photoexcitation of the free PyHC, a photo-induced electron transfer (PET) mechanism may compete with the fluorescence decay to the ground state. In contrast, this PET channel is no longer available in the complex with Mg²⁺ making the emissive decay more efficient. © 2019 Wiley Periodicals, Inc.

Effects of the acceptor unit in dyes with acceptor–bridge–donor architecture on the electron photo-injection mechanism and aggregation in DSSCs

The photo-injection mechanism is influenced by the acceptor motif of dyes in dye-sensitized solar cells (DSSCs).

Novel (E)-1-(pyrrole-2-yl)-3-(aryl)-2-(propen-1-one) derivatives as efficient singlet oxygen quenchers: kinetics and quantum chemical calculations

Kinetics of singlet oxygen (¹O₂) quenching by newly synthesized chalcone derivatives with potential antioxidant applications, and DFT/MRCI calculations.

Internal heavy atom effects in phenothiazinium dyes: enhancement of intersystem crossing via vibronic spin–orbit coupling

The effect of substituting the intra-cyclic sulphur of thionine by oxygen (oxonine) and selenium (selenine) on the intersystem crossing (ISC) efficiency has been studied using high level quantum mechanical methods.