Institut de Chimie Radicalaire

ABSTRACT Geminal bisphosphonate‐functionalized (co)polymers are synthesized via nitroxide‐mediated polymerization (NMP) using gem ‐bisphosphonate‐functionalized vinylbenzyl monomer ( gem BP‐VB), which is first synthesized and fully characterized by 1 H, 13 C, and 31 P NMR as well as by mass spectroscopy. The NMP process yields (co)polymers with narrow dispersity ( Ɖ < 1.3). Subsequently, the gem BP ester groups in these (co)polymers are quantitatively converted into their corresponding bisphosphonic acid functionalities. The chelating ability of the resulting geminal bisphosphonic acid‐containing copolymer, composed of gem BP‐VB and poly(ethylene glycol) methyl ether methacrylate (mPEGMA), is evaluated through its adsorption onto hydroxyapatite (HAp) surfaces. Thermogravimetric analysis reveals an adsorption capacity of 0.105 mmol of phosphonic acid groups per gram of HAp, which exceeds literature values and highlights the potential interest of bisphosphonic‐functionalized (co)polymers in (bio)material applications.

Correction for 'Tracking host-guest recognition in cells by a BODIPY·CB[7] complex' by Fengbo Liu et al., Chem. Commun., 2025, 61, 6675-6678, https://doi.org/10.1039/D5CC00663E.

Our recently developed Direct Reaction field with ESPF Embedding Model (DREEM) method offers an efficient and physically rigorous framework for incorporating polarizable molecular mechanics (MM) environments into quantum mechanics/molecular mechanics (QM/MM) simulations. By coupling the QM and MM regions through the instantaneous MM electrostatic polarization response to QM charge density fluctuations, DREEM enables consistent treatment of ground and excited electronic states, capturing electronic state-specific polarization and dispersion effects absent in conventional mean-field or linear response approaches. The use of electrostatic potential fitting (ESPF) approximation method to describe charge density fluctuations significantly improves the computational efficiency compared the integral-exact direct reaction field. In this work, we present two methodological advancements to extend the applicability of DREEM to realistic condensed-phase simulations. Firstly the development of efficient analytic energy gradients, enabling geometry optimization, transition state searches, and molecular dynamics, and secondly a formulation of periodic boundary conditions (PBC) compatible with the DREEM framework. These capabilities are implemented in the open-source OpenESPF code, interfacing PySCF and OpenMM for high-performance QM and MM calculations. We demonstrate that the resulting implementation enables practical simulations of excited-state optical properties in periodic polarizable environments, where we calculate the fluorescence spectrum of acetone in water including quantum vibronic and non-Condon effects. This paves the way for predictive modeling of photochemical reactivity and spectroscopy in complex systems where environment polarization is important.

Abstract Green synthesis is important in organic synthesis nowadays. Increasing awareness of the need for eco‐friendly technology has led to the use of green techniques in precision chemical and pharmaceutical development. Alternative reaction media that reduce the problems of volatile organic solvents are also gaining popularity. Innovation in reaction media for eco‐friendly, sustainable organic synthesis and the development of important organic heterocycles. Pyrazole and its derivatives are preferred organic heterocycle structures for lead compound identification in the discovery of new synthetic pharmaceutical molecules and other key possibilities. Numerous commercial drugs, such as sildenafil, rimonabant, and celecoxib, in biological and preclinical trials demonstrate the therapeutic breadth of this pharmacological scaffold category. As a green solvent, water is essential for pyrazole derivative synthesis and a convenient reaction medium for organic chemists. This review discusses water's eco‐friendly role in pyrazole derivative synthesis.

Nonadiabatic dynamics simulations complement time-resolved experiments by revealing ultrafast excited-state mechanistic information in photochemical reactions. Understanding the relaxation mechanisms of photoexcited molecules finds application in energy, material, and medicinal research. However, with substantial computational costs, the nonadiabatic dynamics simulations have been restricted to ultrafast timescales, typically less than a few picoseconds, thus neglecting a wide range of photoactivated processes occurring in much longer timescales. Before developing new methodologies, we must ask: How well do the popular nonadiabatic dynamics methods perform in a long timescale simulation? In this study, we employ the multiconfiguration time-dependent Hartree (MCTDH) and its multilayer variants (ML-MCTDH), ab initio multiple spawning (AIMS), and fewest-switches surface hopping (FSSH) methodologies to simulate the excited-states dynamics of a weakly coupled multidimensional Spin-Boson model Hamiltonian designed for a long timescale decay behavior. Our study assures that despite having very different theoretical backgrounds, all the above methods deliver qualitatively similar results. While quantum dynamics would be very costly for long timescale simulations, the trajectory-based approaches are paving the way for future advancements.

A photo-assisted process is explored for improving the synthesis of oligo(triazole amide)s, which are prepared by solid phase synthesis using a repeated cycle of two reactions: amine-carboxylic acid coupling and copper-catalyzed azide-alkyne cycloaddition (CuAAC). The improvement of the second reaction is investigated herein. A catalytic system involving Cu(II)Cl2, N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA)and a titanocene photoinitiator is explored for reducing the reaction time of CuAAC. This catalyst is first tested on a model reaction involving phenylacetylene and ethyl azidoacetate in DMSO. The kinetics of these model experiments are monitored by 1H NMR in the presence of different concentrations of the photoinitiator. It is found that 30 mol% of photoinitiator leads to quantitative reactions in only 8 min. These conditions are then applied to the solid phase synthesis of oligo(triazole amide)s, performed on a glycine-loaded Wang resin. The backbone of the oligomers is constructed using 6-heptynoic acid and 1-amino-11-azido-3,6,9-trioxaundecane as submonomers. Due to slow reagent diffusion, the CuAAC step required more time in the solid phase than in solution. Yet, one hour only is necessary to achieve quantitative CuAAC on the resin, which is twice as fast as previously-reported conditions. Using these optimized conditions, oligo(triazole amide)s of different length are prepared.

Benzo[1,3,2]dithiazole-1,1,3-trioxides are bench-stable and easy-to-use reagents. In photoredox catalysis, they generate methyl and perdeuteromethyl radicals which can add to a variety of radical acceptors, including olefins, acrylamides, quinoxalinones, isocyanides, enol silanes, and N-Ts acrylamide. As byproduct, a salt is formed which can be regenerated to the original methylating agent. Flow chemistry provides an option for reaction scale-up further underscoring the synthetic usefulness of these methylation reagents. Mechanistic investigations suggest a single-electron transfer (SET) pathway induced by photoredox catalysis.

1H photochemicallyinduced dynamic nuclear polarization(photo-CIDNP) has recently emerged as a tool to enhance bulk 1H nuclear magnetic resonance (NMR) signals in solids at magneticfields ranging from 0.3 to 21.1 T, using synthetic donor–chromophore–acceptor(D–C–A) molecules as optically active polarizing agents(PAs). However, the mechanisms at play for the generation of spinpolarization in these systems have not been determined but are essentialfor an in-depth understanding and further development of the process.Here, we introduce site-selective deuteration to identify the 1H photo-CIDNP mechanisms at 85 K and 0.3 T in D–C–Amolecule PhotoPol. We find that the protons on the acceptor moietyare essential for the generation of polarization, establishing differentialrelaxation as the main mechanism. These results establish selectivedeuteration as a tool to identify and suppress polarization transfermechanisms, which opens up pathways for further optimization of theoptical PA at both low and high magnetic fields.