Photoinduced Transformation Research Articles

Photo- thermo-induce changes in As2S3- and As2S3: Au-nanoparticles filled porous glass composite: Optics and the molecular structure simulation of the responsible chalcogenide transformations

In this study we continue a more detailed investigation of the photoinduced effect in nanoporous glass impregnated with As2S3 NPs and Au NPs and its influence on the material's optical properties. The goal of this research is establishing the quantum chemical peculiarities of these processes taking into account the impact of gold nanoparticles on the photoinduced structural transformations of As-S component using Raman spectroscopy and theoretically investigating the molecular structure of arsenic sulfide As-S through ab initio quantum chemical calculations. These support the possibility of further variations in optical properties of such composite materials and photo-thermo driven elements made on their basis.

Spectroscopy and Photochemistry of [Al, N, C, O, H]: Connectivity to Aluminium-Bearing Species in the Universe.

Aluminium is one of the most abundant metals in the universe and impacts the evolution of various astrophysical environments. Currently detected Al-bearing molecules represent only a small fraction of the aluminium budget, suggesting that aluminium may reside in other species. AlO and AlOH molecules are abundant in the oxygen-rich supergiant stars such as VY Canis Majoris, a stellar molecular factory with 60+ molecules including the prebiotic NC-bearing species. Additional Al-bearing molecules with N, C, O, and H may form in O-rich environments with radiation-accelerated chemistry. Here, we present spectroscopic identification of novel aluminium-bearing molecules composed of [Al, N, C, O, H] and [Al, N, C, O] from the reactions of Al atoms and HNCO in solid argon matrix, which are potential Al-bearing molecules in space. Photoinduced transformations among six [Al, N, C, O, H] isomers and three [Al, N, C, O] isomers, along with their dissociation reactions forming the known interstellar species, have been disclosed. These results provide new insight into the chemical network of astronomically detected Al-bearing species in space.

Photochemical method for preparation of benzo[a]pyrano[3,2‐c]phenazin‐4‐ones from quinoxalines with 4‐pyranone unit

AbstractPhotochemical properties of terarylenes with quinoxalines bridge unit and allomaltol fragment was investigated. We have demonstrated that starting compounds with hydroxyl group in 3‐hydroxy‐4‐pyranone substituent does not undergo any photoinduced transformations. Wherein, conversion to methoxy derivatives allows one to realize photochemical 6π‐electrocyclization for considered quinoxalines. Based on data of x‐ray analysis the observed difference in reactivity is connected with the presence of hydrogen bond in hydroxyl derivatives. As a result of carried out research photochemical approach to novel benzo[a]pyrano[3,2‐c]phenazin‐4‐ones was implemented.

Can a bistable amphoteric native defect model explain the photo-induced transformation of MAPbI3 thin films?

Hybrid organic-inorganic perovskites such as MAPbI3 hold great promise for photovoltaic applications with power conversion efficiencies already exceeding 26 %. Despite the unprecedented advantages of these materials in photovoltaics and optoelectronics they exhibit a range of complex phenomena under light illumination that remain poorly understood. Here we use a combination of photoluminescence (PL) spectroscopy, cathodoluminescence imaging and theoretical calculations to correlate PL fluctuations in MAPbI3 thin films with changes in the spatial distribution and concentration of native defects. We demonstrate that short-term illumination results in a more homogeneous distribution of emitting and quenching sites, whereas prolonged illumination causes PL quenching. Our findings support the conclusion that the photo-induced transformation of MAPbI3 can be explained within a bistable amphoteric native defect model, wherein a neutral native defect can undergo a transition between a donor-like and acceptor-like configuration.

Computation assisted chemical study of photo-induced late-stage skeleton transformation of marine natural products towards new scaffolds with biological functions

A computer-assisted chemical investigation of an intriguing photoreaction of norditerpenoids (3‒7) has been first reported, leading to not only their biomimetic conversion, but also the generation of several new products with uncommon 4,14-dioxabicyclo[10.2.1]pentadecane scaffold (8, 9, 12‒14). In bioassay, compounds 10 and 15 exhibited significant stimulation of GLP-1 secretion. This study has given an insight for the application of computational methods on the late-stage skeleton transformation of complex natural products towards new bioactive compounds.

Raman spectroscopy of thermo- and laser-induced transformations of gouache paint layer of copper phthalocyanine blue

Methods to control polymorphic modifications of phthalocyanines using optical (laser) radiation and possible photoinduced transformations of polymorphs are of practical interest in problems of identification and attribution of paintings, laser (micro)sampling, and the development of phthalocyanine structures for technical applications in optics, optoelectronics, and medicine. In this work, we compare the thermal and laser-induced changes of a gouache paint layer based on copper phthalocyanine (CuPc) PB15. The thermally induced color changes of the paint layer are quantified using the CIE Lab D65/10 color space. (Nano)rods formed in the paint layer when the sample is heated to 450°C at normal pressure without humidity control are studied using absorption spectroscopy, Raman microspectroscopy, and scanning electron microscopy. It is shown that the formation of (nano)rods is related to the α→β polymorph transition of CuPc. Low-frequency markers of the CuPc β-polymorph are revealed in the Raman spectra. For the sample containing (nano)rods, the a* color coordinate substantially increases (by about 30 units), whereas the L* and b* coordinates remain almost unchanged. Irradiation with a single nanosecond laser pulse at a wavelength of 532 nm leads to the laser ablation of the paint layer at fluences exceeding a threshold level of about 3 J/cm2. Irradiation at fluences of greater than 0.5 J/cm2, but lower than the ablation threshold leads to color change of the paint layer due to the α→ε transition of CuPc. Similar transformations are observed at the periphery of and inside ablation crater.

Crafting in situ boron and selenium-doped carbon nitride nanosheets for turbocharged benzaldehyde to benzyl alcohol under solar spectrum

This research focuses on the fabrication and application of in situ boron and selenium-doped carbon nitride nanosheets as effective photocatalysts using sun spectrum irradiation to convert turbocharged benzaldehyde to benzyl alcohol. To optimize the doping method for enhanced activity, the effect of changing dopant concentrations on catalytic efficiency was thoroughly investigated. Furthermore, a through analysis of the reactive species involved in the conversion process helped to clarify the photocatalytic process. Based on charge transfer and low recombination, the results indicate that boron and selenium dopants work synergistically to improve catalytic efficiency. This research helps to improve the development of new photocatalytic materials for the sustainable and ecologically friendly transformation of organic molecules under solar spectrum irradiation. The regeneration of NADH using B,Se-CN photocatalyst demonstrates very good efficiency. It also demonstrated the high conversion efficiency of benzaldehyde to benzyl alcohol. This study emphasizes the possible use of B,Se-CN composite in the area of photoinduced conversion-based organic transformation. The knowledge gathered from this research opens up new avenues for the development and enhancement of effective photocatalysts that might be used in a range of solar-powered organic transformation processes.

Photoinduced Transformation of the Orientational Structure of a Chiral Nematic under Planar-Conical Anchoring

The photo-induced change in the orientation structure of the chiral nematic based on LN-396 doped with chiral dopants S811 and cChD has been investigated. It is shown that the use of planar-conical boundary conditions makes it possible to realise a smooth variation of the structure twist angle by changing the helix pitch. It is shown that the twisting of the structure of the studied chiral nematic to an angle of more than 240° leads to undulations when the conical anchoring is specified by the PiBMA polymer. The PtBMA polymer, on the other hand, specifies tangential boundary conditions for the chiral nematic under study, allowing the director to rotate easily in the plane of the sample. The results presented may be promising for the development of liquid crystal systems with finely tunable polar and azimuthal angles of the director.

Unveiling All‐Optical Switching Phenomenon in Anthracene Derivatives: A Comprehensive Study on Optical and Nonlinear Optical Multifunctionality

AbstractIn this study, it is considered three anthracene derivatives, characterized meticulously in terms of their chemical structure and product purity. Extensive quantum chemical calculations are conducted to elucidate their optical and nonlinear optical properties, shedding light on the mechanism of photoinduced conformational transformation, a pivotal discovery in this research. Experimental analyses encompassed fundamental optical properties and advanced nonlinear optical phenomena, including z‐scan experiments, second harmonic generation (SHG), and third harmonic generation (THG). Remarkably, a groundbreaking all‐optical switching phenomenon in these materials is experimentally validated, marking a significant advancement and contributing to their potential applications.

Photocatalysis Meets Confinement: An Emerging Opportunity for Photoinduced Organic Transformations.

The self-assembled metal-organic cages (MOCs) have been evolved as a paradigm of enzyme-mimic catalysts since they are able to synergize multifunctionalities inherent in metal and organic components and constitute microenvironments characteristic of enzymatic spatial confinement and versatile host-guest interactions, thus facilitating unconventional organic transformations via unique driving-forces such as weak noncovalent binding and electron/energy transfer. Recently, MOC-based photoreactors emerged as a burgeoning platform of supramolecular photocatalysis, displaying anomalous reactivities and selectivities distinct from bulk solution. This perspective recaps two decades journey of the photoinduced radical reactions by using photoactive metal-organic cages (PMOCs) as artificial reactors, outlining how the cage-confined photocatalysis was evolved from stoichiometric photoreactions to photocatalytic turnover, from high-energy UV-irradiation to sustainable visible-light photoactivation, and from simple radical reactions to multi-level chemo- and stereoselectivities. We will focus on PMOCs that merge structural and functional biomimicry into a single-cage to behave as multi-role photoreactors, emphasizing their potentials in tackling current challenges in organic transformations through single-electron transfer (SET) or energy transfer (EnT) pathways in a simple, green while feasible manner.

Photocatalysis Meets Confinement: An Emerging Opportunity for Photoinduced Organic Transformations

AbstractThe self‐assembled metal‐organic cages (MOCs) have been evolved as a paradigm of enzyme‐mimic catalysts since they are able to synergize multifunctionalities inherent in metal and organic components and constitute microenvironments characteristic of enzymatic spatial confinement and versatile host–guest interactions, thus facilitating unconventional organic transformations via unique driving‐forces such as weak noncovalent binding and electron/energy transfer. Recently, MOC‐based photoreactors emerged as a burgeoning platform of supramolecular photocatalysis, displaying anomalous reactivities and selectivities distinct from bulk solution. This perspective recaps two decades journey of the photoinduced radical reactions by using photoactive metal‐organic cages (PMOCs) as artificial reactors, outlining how the cage‐confined photocatalysis was evolved from stoichiometric photoreactions to photocatalytic turnover, from high‐energy UV‐irradiation to sustainable visible‐light photoactivation, and from simple radical reactions to multi‐level chemo‐ and stereoselectivities. We will focus on PMOCs that merge structural and functional biomimicry into a single‐cage to behave as multi‐role photoreactors, emphasizing their potentials in tackling current challenges in organic transformations through single‐electron transfer (SET) or energy transfer (EnT) pathways in a simple, green while feasible manner.

Ultrafast and persistent photoinduced phase transition at room temperature monitored by streaming powder diffraction

Ultrafast photoinduced phase transitions at room temperature, driven by a single laser shot and persisting long after stimuli, represent emerging routes for ultrafast control over materials’ properties. Time-resolved studies provide fundamental mechanistic insight into far-from-equilibrium electronic and structural dynamics. Here we study the photoinduced phase transformation of the Rb0.94Mn0.94Co0.06[Fe(CN)6]0.98 material, designed to exhibit a 75 K wide thermal hysteresis around room temperature between MnIIIFeII tetragonal and MnIIFeIII cubic phases. We developed a specific powder sample streaming technique to monitor by ultrafast X-ray diffraction the structural and symmetry changes. We show that the photoinduced polarons expand the lattice, while the tetragonal-to-cubic photoinduced phase transition occurs within 100 ps above threshold fluence. These results are rationalized within the framework of the Landau theory of phase transition as an elastically-driven and cooperative process. We foresee broad applications of the streaming powder technique to study non-reversible and ultrafast dynamics.

Fully Reversible and Super-Fast Photo-Induced Morphological Transformation of Nanofilms for High-Performance UV Detection and Light-Driven Actuators.

Flexible and highly ultraviolet (UV) sensitive materials garner considerable attention in wearable devices, adaptive sensors, and light-driven actuators. Herein, a type of nanofilms with unprecedented fully reversible UV responsiveness are successfully constructed. Building upon this discovery, a new system for ultra-fast, sensitive, and reliable UV detection is developed. The system operates by monitoring the displacement of photoinduced macroscopic motions of the nanofilms based composite membranes. The system exhibits exceptional responsiveness to UV light at 375nm, achieving remarkable response and recovery times of < 0.3s. Furthermore, it boasts a wide detection range from 2.85µWcm-2 to 8.30mWcm-2, along with robust durability. Qualitative UV sensing is accomplished by observing the shape changes of the composite membranes. Moreover, the composite membrane can serve as sunlight-responsive actuators for artificial flowers and smart switches in practical scenarios. The photo-induced motion is ascribed to the cis-trans isomerization of the acylhydrazone bonds, and the rapid and fully reversible shape transformation is supposed to be a synergistic result of the instability of the cis-isomers acylhydrazone bonds and the rebounding property of the networked nanofilms. These findings present a novel strategy for both quantitative and qualitative UV detection.

Multi-stimuli responsive behaviors in a new chiral hybrid nitroprusside salt (R-3-hydroxypyrrolidinium)2[Fe(CN)5(NO)]

Multi-stimuli responsive materials controlled and coupled by two or more channels have a broad range of applications in the field of switches, memories, and molecular machines. The exploration of the material is currently focused on the pure organic system, which limits the development of such materials greatly. In this work, we present a new chiral organic-inorganic hybrid salt, (R-3-hydroxypyrrolidinium)2[Fe(CN)5(NO)] (1), which exhibits rare multi-stimuli responsive behaviors in thermal, mechanical and optical channels. In detail, 1 undergoes a C2-P21221 phase transition deriving from the thermal motion of organic cations with the increase of temperature, but the reverse transition can only be induced by mechanical pressure. Moreover, polycrystalline hybrid salt showed photo-responsive performance, i.e., the ground-state N-bound nitrosyl ligand adopts two configurations in excited states caused by light in 532 nm irradiation, accompanying with a photo-induced structural transformation of the anionic framework. Namely, the thermal motion characteristics of organic cations, the photoresponse characteristics of anionic inorganic skeleton and the pressure characteristics from hydrogen bonds are simultaneously integrated in 1. This unprecedented coupling mechanism of multi-stimuli responses makes 1 a potential candidate for future multichannel data storage applications.

A Continuous-Wave EPR Investigation into the Photochemical Transformations of the Chromium(I) Carbonyl Complex [Cr(CO)4bis(diphenylphosphino)]+ and Reactivity with 1-hexene.

Chromium complexes containing a bis(diphenylphosphino) ligand have attracted significant interest over many years due to their potential as active catalysts for ethylene oligomerisation when combined with suitable co-catalysts such as triethylaluminium (TEA) or methylaluminoxane (MAO). While there has been considerable attention devoted to the possible reaction intermediates and the nature of the Cr oxidation states involved, the potential UV photoactivity of the Cr(I) complexes has so far been overlooked. Therefore, to explore the photoinduced transformations of bis(diphenylphosphino) stabilized Cr(I) complexes, we used continuous-wave (CW) EPR to study the effects of UV radiation on a cationic [Cr(CO)4(dppp)]+[Al(OC(CF3)3)4]- complex (1), where dppp represents the 1,3 bis-(diphenylphosphino)propane ligand, Ph2P(C3H6)PPh2. Our preliminary investigations into the photochemistry of this complex revealed that [Cr(CO)4(dppp)]+ (1) can be readily photo-converted into an intermediate mer-[Cr(CO)3(κ1-dppp)(κ2-dppp)]+ complex (2) and eventually into a trans-[Cr(CO)2(dppp)2]+ complex (3) in solution at room temperature under UV-A light. Here, we show that the intermediate species (2) involved in this transformation can be identified by EPR at much lower temperature (140 K) and at a specific wavelength (highlighting the wavelength dependency of the reaction). In addition, small amounts of a 'piano-stool'-type complex, namely [Cr(CO)2(dppp-η6-arene)]+ (4), can also be formed during the photoconversion of [Cr(CO)4(dppp)]+ using UV-A light. There was no evidence for the formation of the [Cr(L-bis-η6-arene)]+ complex (5) in these UV irradiation experiments. For the first time, we also evidence the formation of a 1-hexene coordinated [Cr(CO)3(dppp)(1-hexene)]+ complex (6) following UV irradiation of [Cr(CO)4(dppp)]+ in the presence of 1-hexene; this result demonstrates the unprecedented opportunity for exploiting light activation during Cr-driven olefin oligomerisation catalysis, instead of expensive, difficult-to-handle, and hazardous chemical activators.

A new era of LMCT: leveraging ligand-to-metal charge transfer excited states for photochemical reactions.

Ligand-to-metal charge transfer (LMCT) excited states are capable of undergoing a wide array of photochemical reactions, yet receive minimal attention compared to other charge transfer excited states. This work provides general criteria for designing transition metal complexes that exhibit low energy LMCT excited states and routes to drive photochemistry from these excited states. General design principles regarding metal identity, oxidation state, geometry, and ligand sets are summarized. Fundamental photoreactions from these states including visible light-induced homolysis, excited state electron transfer, and other photoinduced chemical transformations are discussed and key design principles for enabling these photochemical reactions are further highlighted. Guided by these fundamentals, this review outlines critical considerations for the future design and application of coordination complexes with LMCT excited states.

Photoinduced morphological transformation of a self-assembled iron(ii) coordination polymer: high-performance, non-precious metal, and self-enhancing photocatalytic CO2 reduction

Herein, uncommon self-enhancing photocatalysis has been demonstrated through photoinduced morphology transformation of a self-assembled iron coordination polymer for CO2 photoreduction.

Photo-induced radical transformations of tosyl cyanide.

Tosyl cyanide is a commonly used reagent for cyanation and sulfonylation in organic synthesis and pharmaceutical chemistry. The photocatalytic transformations of tosyl cyanide are generally conducted under mild conditions. This minireview summarizes the recent progress of radical-involved transformations of tosyl cyanide via photo-induced cyanation or sulfonylcyanation.

Photocatalyst‐ and Transition‐Metal‐Free Light‐Induced Formation of Carbon‐Chalcogen Bonds

AbstractPhotoinduced chemical transformations have become a promising aspect of organic synthesis. This review focuses on the recent advancements in harnessing photoinduced processes for the formation of carbon‐chalcogen (C−O, C−S, C−Se, and C−Te) bonds under catalyst‐free conditions. These pathways typically involve either a radical mechanism or the creation of electron‐donor‐acceptor (EDA) complexes. The review explores the intricacies of the underlying mechanisms, discusses limitations, and evaluates the applicability of various methodologies in this field. Notably, photocatalyst and transition metal‐free photochemical reactions offer effective alternatives to enhance sustainability in this research area.

Ultrafast Photocontrolled Rotation in a Molecular Motor Investigated by Machine Learning-Based Nonadiabatic Dynamics Simulations.

The thermal helix inversion (THI) of the overcrowded alkene-based molecular motors determines the speed of the unidirectional rotation due to the high reaction barrier in the ground state, in comparison with the ultrafast photoreaction process. Recently, a phosphine-based motor has achieved all-photochemical rotation experimentally, promising to be controlled without a thermal step. However, the mechanism of this photochemical reaction has not yet been fully revealed. The comprehensive computational studies on photoisomerization still resort to nonadiabatic molecular dynamics (NAMD) simulations based on electronic structure calculations, which remains a high computational cost for large systems such as molecular motors. Machine learning (ML) has become an accelerating tool in NAMD simulations recently, where excited-state potential energy surfaces (PESs) are constructed analytically with high accuracy, providing an efficient approach for simulations in photochemistry. Herein the reaction pathway is explored by a spin-flip time-dependent density functional theory (SF-TDDFT) approach in combination with ML-based NAMD simulations. According to our computational simulations, we notice that one of the key factors of fulfilling all-photochemical rotation in the phosphine-based motor is that the excitation energies of four isomers are similar. Additionally, a shortcut photoinduced transformation between unstable isomers replaces the THI step, which shares the conical intersection (CI) with photoisomerization. In this study, we provide a practical approach to speed up the NAMD simulations in photochemical reactions for a large system that could be extended to other complex systems.