Trapping Highly Reactive Photo-Induced Charge-Transfer Complex Between Amine and Imide by Light

Complexation between two organic molecules can occur either for strong electron donor-acceptor pairs in the ground state known as charge-transfer complexes (CTCs), or for pairs of lesser strength in the excited state such as excimers and exciplexes. However, the characterization of chemically distinct CTCs in solution remains elusive. Here, we report a light-induced, solution-persistent 1:1 CTC between an amine and an imide. The pair is not associated in the ground state at room temperature prior to light exposure. The presence and exact molecular compositions of the CTCs could be directly obtained from high-resolution mass spectrometry. Additional spectroscopic and computational evidence reveals that a kinetically trapped ground-state pair is formed following an exciplex-like process between the amine and the imide after photo-excitation. We show that such a photo-induced complex can be used to conduct photochemistry and store photon energy for producing otherwise photochromic products in the dark

N-H Insertion of Anilines on N-Tosylhydrazones Induced by Visible Light Irradiation

Diazo compounds as well as their precursors represent an interesting category for organic synthesis. Particularly N-tosylhydrazones, have attracted attention for their easy accessibility and diverse reactivity, including carbene transfer reactions. We described a visible light induced N-H insertion reaction of anilines on in-situ generated diazo compounds. Optimal conditions using DBU in toluene yielded desired products efficiently. Mechanistic studies enabled us to trap a carbene intermediate that has a key role in this transformation

Enantioselective Synthesis of Sulfinamidines via Asymmetric Nitrogen Transfer from N-H Oxaziridines to Sulfenamides

Sulfinamidines are promising aza-SIV chiral building blocks in asymmetric synthesis and drug discovery. However, no report has documented their enantioselective synthesis. Here we present an enantioselective synthesis of sulfinamidines via electrophilic amination of sulfenamides using an enantiopure N-H oxaziridine. The resulting enantiomerically enriched primary sulfinamidines are configurationally stable at 90 oC in solution. We also demonstrate a one-pot, three-component, enantioselective synthesis of sulfinamides using N-H oxaziridine reagents

Pd(COD)(DQ): A Stable, Versatile, and Monometallic Palladium(0) Source for Organometallic Synthesis and Catalysis

Pd(COD)(DQ) (COD=1,5-cyclooctadiene, DQ=duroquinone) is a robust, air-stable, and well-defined 18-electron Pd(0)–olefin complex first synthesized by Sakai et al. in 1983. Herein, we describe an operationally convenient synthetic procedure to prepare this complex on decagram scale; we show that it undergoes facile ligand exchange with phosphines, N-heterocyclic carbenes, and other catalytically important ancillary ligands to give stable organometallic products; and we demonstrate its catalytic competence in numerous useful reactions in organic synthesis. We anticipate that the pronounced stability of Pd(COD)(DQ) and its favorable handling properties will allow it to find use as a convenient Pd(0) source in academic and industrial research labs

On analytical corrections for restraints in absolute binding free energy calculations

Double decoupling absolute binding free energy simulations require an intermediate state at which the ligand is held solely by restraints in a position and orientation resembling the bound state. One possible choice consists of one distance, two angle and three dihedral angle restraints. Here, I demonstrate that in practically all cases, the analytical correction derived under the rigid rotator harmonic oscillator approximation is sufficient to account for the free energy of the restraint

Using Reaktoro for mineral and gas solubility calculations with the Extended UNIQUAC model

The extended UNIQUAC model is a thermodynamic model able to estimate thermodynamic properties of aqueous electrolyte solutions under a wide range of temperature, pressure, and composition conditions. Thermodynamic properties include species activity coefficients, excess molar Gibbs energy, excess molar enthalpy, excess molar heat capacity. These properties are important for aqueous speciation calculations, mineral and gas solubility computations, chemical kinetic modeling of mineral dissolution and precipitation, and in reactive transport simulations considering chemically complex aqueous electrolyte solutions. In this paper we present a brief literature review on the extended UNIQUAC model, we report on its im-plementation in C++ in the Reaktoro framework for modeling chemically reactive systems, and we show its use from Python for computing mineral and gas solubilities in aqueous solutions at a wide range of temperature, pressure, and salinity conditions. We validated the calculations against experimental data and against results obtained through the software ScaleCERE implementing the extended UNIQUAC model. Our conclusion is that the extended UNIQUAC model has been successfully implemented into the Reaktoro framework, thereby providing a suitable activity model for geochemical and reactive transport modeling

Water, Energy, and Cost: A Nexus Approach to Zero/Minimal Liquid Discharge Desalination Technologies

Desalination is increasingly essential to ensure water access as climate change and population growth stress fresh water supplies. Already in use in water-stressed regions around the world, desalination generates fresh water from salty sources, but forms a concentrated brine that requires disposal. There is a growing push for the adoption of zero/minimal liquid discharge (ZLD/MLD) technologies that recover additional water from this brine while reducing the liquid volumes requiring disposal. This analysis evaluates the cost, energy, and sustainability impacts of 7 overarching treatment trains with 75 different configurations. ZLD/MLD water recoveries are found to range from 32.6-98.6%, but with steep energy and cost tradeoffs that underscore the crucial role of ion-specific separations, heat integration, and clean energy sources. Ultimately, this analysis explores key tradeoffs between costs, energy, and water recovery, highlighting the increasingly tight connections at the central to the energy-water nexus and desalination

The Development of the QM/MM Interface and Its Application for the on-the-fly QM/MM Nonadiabatic Dynamics in JADE Package: Theory, Implementation and Applications

Understanding the nonadiabatic dynamics of complex systems is a challenging task in computational photochemistry. Herein, we present an efficient and user-friendly quantum mechanics/molecular mechanics (QM/MM) interface to run on-the-fly nonadiabatic dynamics. Currently, this interface consists of an independent set of codes designed for general-purpose use. Herein, we demonstrate the ability and feasibility of the QM/MM interface by integrating it with our long-term developed JADE package. Tailored to handle nonadiabatic processes in various complex systems, especially condensed phases and protein environments, we delve into the theories, implementations, and applications of the on-the-fly QM/MM nonadiabatic dynamics. The QM/MM approach is established within the framework of the additive QM/MM scheme, employing electrostatic embedding, link-atom inclusion, and charge-redistribution schemes to treat the QM/MM boundary. Trajectory surface-hopping dynamics are facilitated using the fewest switches algorithm, encompassing classical and quantum treatments for nuclear and electronic motions, respectively. Finally, we report simulations of nonadiabatic dynamics for two typical systems: azomethane in water and the retinal chromophore PSB3 in a protein environment. Our results not only illustrate the power of the QM/MM program but also reveal the important roles of environmental factors in nonadiabatic processes

Continuous flow synthesis of N,O-dimethyl-N\u27-nitroisourea monitored by inline FTIR: comparing machine learning and kinetic modeling for optimization

The synthesis of N,O-Dimethyl-N\u27-nitroisourea, crucial intermediates in pesticide manufacturing, was explored through a substitution reaction between O-methyl-N-nitroisourea and methylamine within a novel continuous flow microreactor system, featuring FTIR inline analysis for real-time monitoring. This study embarked on a comparative analysis between two optimization approaches: the contemporary machine learning-based Bayesian optimization and the traditional kinetic modeling. Remarkably, both strategies obtained a similar yield of approximately 83 % under equivalent reaction parameters---specifically, an initial reactant concentration of 0.2 mol/L, a reaction temperature of 40 °C, a molar ratio of reactants at 5:1, and a residence time of 240 minutes. The Bayesian optimization method demonstrated a notable efficiency, achieving optimal conditions within a mere 20 experiments, in contrast to the kinetic modeling approach, which required a more laborious effort for model formulation and validation. Despite the long-standing reliance on kinetic modeling for its detailed insights into reaction dynamics, our findings suggest its relative inefficiency in optimization tasks compared to the machine learning-based alternative. This study not only highlights the potential of integrating advanced machine learning methods into chemical process optimization but also sets the stage for further exploration into efficient, data-driven approaches in chemical synthesis

Strongly photoreducing organic donor-acceptor thermally activated delayed fluorescence photocatalysts

We report a family of donor-acceptor thermally activated delayed fluorescent (TADF) compounds based on derivatives of DMAC-TRZ, that are strongly photoreducing. Both Eox and thus E*ox could be tuned via substitution of the DMAC donor with a Hammett series of p-substituted phenyl moieties while Ered remained effectively constant. These compounds were assessed in the photoinduced dehalogenation of aryl halides, and analogues bearing electron withdrawing groups were found to produce the highest yields. Substrates of up to Ered = -2.72 V could be dehalogenated at low PC loading (1 mol%) and under air, conditions much milder than previously reported for this reaction. Spectroscopic and chemical studies demonstrate that all PCs, including literature reference PCs, photodegrade, and that it is these photodegradation products that are responsible for the reactivity