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Investigating the Photochemistry of Spiropyran Metal Complexes with Online LED-NMR
摘要： As one of the best studied photoswitches, spiropyrans (SPs) have attracted significant interest in the scientific community. Among the many stimuli to alter the isomerization into the merocyanine (MC) isomer, such as temperature, pH, solvent polarity, redox potential, or mechanical force, the ability of the MC form to act as a ligand site for metal complexation has recently raised new attention. We herein synthesize hitherto undescribed coordination compounds of 8-methoxy-1′,3′,3′-trimethyl-6-nitrospiro-[chromene-2,2′-indoline] with s-block ([Ca(MC)4](ClO4)2), d-block ([Zn(MC)2(MeCN)2](ClO4)2, [Ni(MC)2(MeCN)2](ClO4)2), as well as f-block ([La(NO3)3(MC)2]) metals. All complexes are structurally described by X-ray crystallography and systematically investigated in solution via Job’s method of continuous variations (Job plots), as well as online NMR spectroscopic kinetic experiments with in situ irradiation of the analyte solution inside the NMR spectrometer (LED-NMR). We can unambiguously identify the photoresponsive nature of the complexes in solution, which is a crucial step toward the application of these promising molecules in material science.
关键词： photochemistry,LED-NMR,metal complexes,X-ray crystallography,spiropyrans
更新于2025-09-23 15:19:57
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Enantioselective ?±-Allylation of Anilines Enabled by a Combined Palladium and Photoredox Catalytic System
摘要： An enantioselective and branch-regioselective α-allylation of N-methyl anilines under dual palladium/photoredox catalysis is described. Readily available N-methyl anilines are used as formal “hard” alkyl nucleophiles without pre-activation. Acetic acid is the only side product, which leads to high atom economy of this reaction. This protocol shows good functional group tolerance and broad scope. A range of chiral homoallylic amines were prepared in moderate to good yields (up to 76%), excellent regio- (B:L > 95:5 in all cases) and enantioselectivities (up to 96% ee) under mild reaction conditions.
关键词： asymmetric allylation,photochemistry,photoredox catalysis,cooperative catalysis,palladium
更新于2025-09-23 15:19:57
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Hydrogen and Sulfonyl Radical Generation for the Hydrogenation and Arylsulfonylation of Alkenes Driven by Photochemical Activity of Hydrogen Bond Donor-Acceptor Complexes
摘要： An efficient photoinduced strategy for the hydrogenation and arylsulfonylation of alkenes has been developed. The reaction afforded a range of hydrogenated products and sulfonated oxindoles in high yields under external photocatalyst-free, oxidant- and reductant-free conditions. Mechanistic investigations suggested that this transformation is driven by the photochemical activity of hydrogen bond donor-acceptor complex, generated from the substrates of arylsulfinic acids and C6-(vinyl sulfone)phenanthridines or N-arylacrylamides via hydrogen bond interaction.
关键词： arylsulfinic acids,alkenes,photochemistry,radical transformation,hydrogen bond interaction
更新于2025-09-19 17:15:36
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Sub-Femtosecond Stark Control of Molecular Photoexcitation With Near Single-Cycle Pulses
摘要： Electric fields can tailor molecular potential energy surfaces by interaction with the electronic state-dependent molecular dipole moment. Recent developments in optics have enabled the creation of ultra-short few-cycle optical pulses with precise control of the carrier envelope phase (CEP) that determines the offset of the maxima in the field and the pulse envelope. This opens news ways of controlling ultrafast molecular dynamics by exploiting the CEP. In this work, we show that the photoabsorption efficiency of oriented H2CSO (sulfine) can be controlled by tuning the CEP. We further show that this control emanates from a resonance condition related to Stark shifting of the electronic energy levels.
关键词： ultrafast photochemistry,Ab initio multiple spawning (AIMS),few-cycle pulse,Stark effect,excited state dynamics
更新于2025-09-19 17:15:36
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Synthesis of photocaged diamines and their application in photoinduced self-assembly
摘要： The photochemical cleavage of covalent bonds is an important strategy in protection group chemistry, as well as for the triggering of chemical events posterior to the application of the physicochemical stimulus. Photocages allow the arresting and traceless liberation of a chemical entity, which can be broadly applied as a functional control element in materials chemistry and the life sciences in general. Among the best studied and most versatile light-sensitive protecting groups known to date rank the o-nitrobenzyl derivatives, entities which are easily introduced to amines, thiols, and alcohols. Their photolability relies on a phototautomerisation-induced cleavage mechanism, a phenomenon largely dependent on the substitution pattern of the aromatic ring in the o-nitrophenyl-moiety. Although well described and studied in detail for the protection of amino groups of different nature, the photocaging of aliphatic diamines has not been described in detail to date. Because of their interesting properties as synthons in supramolecular and polymer chemistry alike, we wish to describe the efficient photocaging of diamines with o-nitrobenzyl derivatives, their photocleavage behavior over time, as well as their application in a photoinduced templated self-assembly reaction towards cyclic imines.
关键词： physicochemical stimuli,photochemistry,self-assembly,imine formation,photocaging,diamines
更新于2025-09-19 17:15:36
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Photocatalyzed thiol-alkene coupling: Mechanistic study and polymer synthesis
摘要： Due to the “click” chemistry characteristics of the thiol–ene reaction, these transformations have been gaining an increasing amount of attention in current chemical research. The high efficiency and selectivity of these transformations have been useful for many areas of study, from small molecule organic synthesis, to polymer synthesis and functionalization, to bioconjugation reactions. In this work, a study of a novel method of photochemical thiol–ene reactions using alkyl halides and an tris [2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)3) photocatalyst is investigated. This process is shown to progress rapidly and has the benefit of low catalyst and initiator concentrations relative to reagents as well as mild conditions associated with photochemical processes. To understand the mechanism of this process, catalyst and initiator concentrations and other reaction conditions are varied. To demonstrate the utility of this process, a step-growth thiol–ene polymer is synthesized using dithiol and diene monomers and a crosslinked polymer network is synthesized as well.
关键词： thiol–ene,radical reactions,step-growth polymerization,polymer network,photochemistry
更新于2025-09-19 17:15:36
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Discovery of conical intersection mediated photochemistry with growing string methods
摘要： Conical intersections (CIs) are important features of photochemistry that determine yields and selectivity. Traditional CI optimizers require significant human effort and chemical intuition, which typically restricts searching to only a small region of the CI space. Herein, a systematic approach utilizing the growing string method is introduced to locate multiple CIs. Unintuitive MECI are found using driving coordinates that can be generated using a combinatorial search, and subsequent optimization allows reaction pathways, transition states, products, and seam-space pathways to be located. These capabilities are demonstrated by application to two prototypical photoisomerization reactions and the dimerization of butadiene. In total, many reaction pathways were uncovered, including the elusive stilbene hula-twist mechanism, and a previously unidentified product in butadiene dimerization. Overall, these results suggest that growing string methods provide a predictive strategy for exploring photochemistry.
关键词： reaction pathways,growing string method,conical intersections,photochemistry,MECI
更新于2025-09-19 17:15:36
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Photoinduced reversible solid-to-liquid transitions using photoswitchable materials
摘要： Heating and cooling can induce reversible solid-to-liquid transitions of matter. In contrast, athermal photochemical processes can induce reversible solid-to-liquid transitions of some newly developed azobenzene compounds. Azobenzene is photoswitchable. UV light induces trans-to-cis isomerization; visible light or heat induces cis-to-trans isomerization. Trans and cis isomers usually have different melting points (Tms) or glass transition temperatures (Tgs). If Tms or Tgs of an azobenzene compound in trans and cis forms are above and below room temperature, respectively, light may induce reversible solid-to-liquid transitions. In this review, we introduce azobenzene compounds that exhibit photoinduced reversible solid-to-liquid transitions, discuss the mechanisms and design principles, and show their potential applications in healable coatings, adhesives, transfer printing, lithography, actuators, fuels, and gas separation. Finally, we discuss remaining challenges in this field.
关键词： photoswitch,isomerization,azobenzene,solid-to-liquid transition,photochemistry
更新于2025-09-19 17:15:36
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The Role of Hydrogen-Bond Between Piperazine and Fullerene Molecules in Stabilizing Polymer:Fullerene Solar Cell Performance
摘要： Piperazine was recently reported as stabilizer for polymer:fullerene solar cells that can minimize the “burn-in” degradation of the cell. In this paper, the influence of N-substituents on the stabilization effect of piperazine in P3HT:PC61BM cells was investigated. Results confirmed that only piperazine derivatives (PZs) with N-H bond showed the stabilization effect, whereas the bis-alkyl substituted piperazine compounds do not able to improve the stability. Efficient photon-induced electron transfer (PET) process between PZ and PC61BM was only detected for the N-H containing PZ:PC61BM blends, corresponding ver well the stabilization effect of the PZs, which indicates that PET process of PZ and PC61BM stabilize the cell performance and the N-H bond plays a critical role ensuring the PET process and the consequent stabilization effect. Both 1H-NMR spectroscopy and theoretical calculation confirmed the formation of N-H…O-C and N-H…π bonds for the PC61BM-piperazine adduct, which was considered as the driving force that promotes the PET process between these two components. In addition, comparison of the calculated electron affinity energy (EA) and excitation energy (EEx) of PC61BM with/without piperazine confirmed that piperazine doping is able to promote the electron transfer (leads to the formation of PC61BM anions) than the energy transfer (leads to the formation of PC61BM excitons) between P3HT and PC61BM, which is beneficial for the performance and stability improvement.
关键词： Piperazine,Photochemistry,Degradation and Stability,Polymer Solar Cells,Hydrogen Bond
更新于2025-09-19 17:13:59
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Blue LED Irradiation of Iodonium Ylides Gives Diradical Intermediates for Efficient Metal-free Cyclopropanation with Alkenes
摘要： A facile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and b-dicarbonyl-derived iodonium ylides are irradiated with light from blue LEDs. This metal-free synthesis gives cyclopropanes in yields up to 96 %, is operative with cyclic and acyclic ylides, and proceeds with a variety of electronically-diverse alkenes. Computational analysis explains the high selectivity observed, which derives from exclusive HOMO to LUMO excitation, instead of free carbene generation. The procedure is operationally simple, uses no photocatalyst, and provides access in one step to important building blocks for complex molecule synthesis.
关键词： hypervalent iodine,cyclopropanation,LED photochemistry,iodonium ylides,computational analysis
更新于2025-09-19 17:13:59