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Abstract Phosphiranes are weak Lewis bases reacting with only a limited number of electrophiles to produce the corresponding phosphiranium ions. These salts are recognized for their propensity to undergo reactions with oxygen pronucleophiles at the phosphorus site, leading to the formation of phosphine oxide adducts. Building on a thorough mechanistic understanding, we have developed an unprecedented approach that enables the selective reaction of carboxylic acids, and other nucleophiles, at the carbon site of phosphiranes. This method involves the photochemical generation of highly reactive carbenes, which react with 1‐mesitylphosphirane to yield ylides. The latter undergoes a stepwise reaction with carboxylic acids, resulting in the production of the desired phosphines. In addition to DFT calculations, we have successfully isolated and fully characterized the key intermediates involved in the reaction.
Photocatalysis that uses the energy of light to promote chemical transformations by exploiting the reactivity of excited-state molecules is at the heart of a virtuous dynamic within the chemical community. Visible-light metal-based photosensitizers are most prominent in organic synthesis, thanks to their versatile ligand structure tunability allowing to adjust photocatalytic properties toward specific applications. Nevertheless, a large majority of these photocatalysts are cationic species whose counterion effects remain underestimated and overlooked. In this report, we show that modification of the X counterions constitutive of [Ru(bpy)<sub>3</sub>](X)<sub>2</sub> photocatalysts modulates their catalytic activities in intermolecular [2 + 2] cycloaddition reactions operating through triplet–triplet energy transfer (TTEnT). Particularly noteworthy is the dramatic impact observed in low-dielectric constant solvent over the excited-state quenching coefficient, which varies by two orders of magnitude depending on whether X is a large weakly bound (BAr$^F$<sub>4</sub>$^–$) or a tightly bound (TsO$^–$) anion. In addition, the counterion identity also greatly affects the photophysical properties of the cationic ruthenium complex, with [Ru(bpy)<sub>3</sub>](BAr$^F$<sub>4</sub>)<sub>2</sub> exhibiting the shortest 3MLCT excited-state lifetime, highest excited state energy, and highest photostability, enabling remarkably enhanced performance (up to >1000 TON at a low 500 ppm catalyst loading) in TTEnT photocatalysis. These findings supported by density functional theory-based calculations demonstrate that counterions have a critical role in modulating cationic transition metal-based photocatalyst potency, a parameter that should be taken into consideration also when developing energy transfer-triggered processes.
Abstract Chiral molecules, used in applications such as enantioselective photocatalysis 1 , circularly polarized light detection 2 and emission 3 and molecular switches 4,5 , exist in two geometrical configurations that are non-superimposable mirror images of each other. These so-called ( R ) and ( S ) enantiomers exhibit different physical and chemical properties when interacting with other chiral entities. Attosecond technology might enable influence over such interactions, given that it can probe and even direct electron motion within molecules on the intrinsic electronic timescale 6 and thereby control reactivity 7–9 . Electron currents in photoexcited chiral molecules have indeed been predicted to enable enantiosensitive molecular orientation 10 , but electron-driven chiral dynamics in neutral molecules have not yet been demonstrated owing to the lack of ultrashort, non-ionizing and perturbative light pulses. Here we use time-resolved photoelectron circular dichroism (TR-PECD) 11–15 with an unprecedented temporal resolution of 2.9 fs to map the coherent electronic motion initiated by ultraviolet (UV) excitation of neutral chiral molecules. We find that electronic beatings between Rydberg states lead to periodic modulations of the chiroptical response on the few-femtosecond timescale, showing a sign inversion in less than 10 fs. Calculations validate this and also confirm that the combination of the photoinduced chiral current with a circularly polarized probe pulse realizes an enantioselective filter of molecular orientations following photoionization. We anticipate that our approach will enable further investigations of ultrafast electron dynamics in chiral systems and reveal a route towards enantiosensitive charge-directed reactivity.
Sujets
Excited states
Quinones
Photochromism
KOHN-SHAM ORBITALS
Complexes de Ruthénium à Ligand Nitrosyle
DFT
Oxidation
3MLCT
Complexe de coordination
Coordination compounds
Metalloporphyrin
Aggregation induced emission AIE solid state luminescence enhancement SLE ESIPT photoluminescence crystal structure SF-TD-DFT
Diarylethenes
Electrochemistry
CROSS-SECTIONS
Multiple bonds
Photosubstitution
Aggregation induced emission AIE
Chimie théorique
Computational photochemistry
Photoisomerization Mechanism
Metal-centered excited states
Excited States
Dithienylethene
Mathematical methods
DER-WAALS COMPLEXES
Phosphirane phosphorus mechanism photochemistry selectivity
Hydrolysis
Groundwaters
Chimie Théorique et Computationnelle
Density Functional Theory DFT
2+2 cycloaddition
Molecular orbitals
Photosolvolysis mechanism
Electrochemical reduction
Orbitales moléculaires
Lanthanides
Photophysics
Rhenium
Crystal
Insertion reaction
RASPT2
DENSITY-FUNCTIONAL THEORY
PERTURBATION-THEORY APPROACH
Redox reactions
Organic semiconductor
Nitric oxide
Photochromisme
Phosphorescence
Photochromes
Carbonate
INFRARED-SPECTRUM
Photoluminescence
ACETYLENE
Counterion effects
Phosphirane
Iron
Electrochemical properties
DIMER
ESIPT
Inorganic chemistry
Ruthénium
Photocatalysis
Quantum mechanics
Density functional calculations
Photochimie
IPEA
Ruthenium complex
Photorelease
Photophysique
Photoisomerization
Ab initio
Chimie Théorique
DFT computations
Mechanism
3MC
Nudged elastic band
Mechanoresponsive luminescence
Photochemistry
Mécanisme de Photoisomérisation
Photochimie Computationnelle
Modeling
Ruthenium
Photoisomérisation
ICP-MS
Density functional theory
Computational Photochemistry
Actinides
Ion-molecule reactions
Etats Excités
Phosphorus
Crystal structure
Photorelease Mechanism
NBO
Mécanisme de Photolibération
Nitrosyl Ruthenium Complexes
Chimie inorganique
MOLECULES
Photodissociation
Ab initio calculations