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Lower Critical Solution Temperature (LCST) of macromolecular systems is important in thermoresponsive smart window design. However, controlling the LCST behavior and sustaining the shelf‐life are challenging tasks. Herein, how photochemistry can be tweaked to design sustainable smart windows that allow controlled transmission of solar radiation is described. The cyanostilbene substituted naphthalenes 1(Z) and 2(Z), show Z/E‐photoisomerization and subsequent Mallory cyclization resulting in significant modulation in clouding temperatures (Tcloud). At 1 mM concentration, the Tcloud of 1(Z), and 1(E) are 33 ± 0.1 and 28 ± 0.13 °C, respectively whereas 2(Z) and 2(E) exhibit Tcloud around 37 ± 0.1 and 30 ± 0.1 °C, respectively. The high thermal barrier for the E/Z back isomerization of 1(E) and 2(E) and removal of oxygen from the reaction medium allow control of the photoprocesses, thereby facilitating the construction of sustainable smart windows that respond to the surrounding temperature. A 30 × 30 cm2 window prototype containing an aqueous solution of 1(Z) (1 mM) exhibits a fully transmissive state at 25 °C and a nearly zero‐transmissive state at 33 °C for 10,000 cycles of operation. [ABSTRACT FROM AUTHOR]

Photomodulable fluorophores constitute advanced materials as they possess the ability to modify their photophysical properties upon photoirradiation. A new mechanism of photoconversion is recently established, called Directed Photooxidation Induced Conversion based on the coupling of fluorophores with Aromatic Singlet oxygen Reactive Moieties (ASORMs). In this work, The Directed Photooxidation Induced Conversion (DPIC) mechanism is intended to be applied to Perylene BisImide (PBI) due to its appealing photophysical properties. The experimental results showed that coupling two ASORMs to the PBI core, here furan and pyrrole, led to impressive photomodulable fluorophores. While PBI‐F exhibited a photoconversion of 100 nm shift, PBI‐P displayed an 80‐fold fluorescence intensity enhancement upon photoactivation. Analysis of the photoproducts showed that the conversion do not involve an addition of singlet oxygen on the ASORM. Instead, photoconversion occurred through efficient successive photocyclizations. Finally, intracellular vesicles are successfully photoconverted by means of endocytosed PLGA‐polymer nanoparticles loaded with PBI‐F. This study highlights the unique capability of furan‐ and pyrrole‐conjugated fluorophores to enable advanced optical materials with phototransformation properties. [ABSTRACT FROM AUTHOR]

Herein, corannulene‐based quintuple [6]helicenes (Q[6]H‐1 and Q[6]H‐2) and [7]helicene (Q[7]H) were synthesized via penta‐fold Heck and Mallory reaction. Notably, Q[7]H represents the highest reported helicene based on corannulene. X‐ray crystallography reveals that Q[6]H‐2 adopts a propeller‐shaped conformation with a well‐preserved corannulene core, while Q[6]H‐1 and Q[7]H exhibit quasi‐propeller‐shaped conformations. Upon heating, conformer Q[6]H‐1 undergoes conversion to the thermodynamically more stable conformer Q[6]H‐2, whereas conformer Q[7]H remains unchanged due to larger steric congestion. Racemization of the enantiomer of Q[6]H‐1 and conformational conversion were observed simultaneously at elevated temperature, with DFT studies indicating a racemization barrier of 32.06 kcal ⋅ mol−1. In contrast, the racemization barrier for Q[6]H‐2 was calculated to be 45.46 kcal ⋅ mol−1, indicating exceptional chiral stability. Surprisingly, the bowl inversions of Q[6]H‐1 and Q[6]H‐2 conformers are somewhat inhibited by the helical blades, whereas this was not observed for other possible conformers of Q[6]H. These results first demonstrated that subtle conformational variations can lead to significant changes in chiral stability and bowl inversions of multiple helicenes. Due to the well‐preserved corannulene core, propeller‐shaped conformation and electron complementarity, Q[6]H‐2 can recognize fullerenes in both solution and solid state, which is a rare instance of co‐crystallization assembly between multiple helicenes and fullerenes. [ABSTRACT FROM AUTHOR]

The conductance of a tunneling electron through a π-conjugated molecule may be affected by the presence of different pathways in the orbital structure of the molecule, resulting in the constructive or destructive interference of the molecular wave function. This quantum interference (QI) directly translates into enhancement or suppression of conductance and offers the possibility of controlling this phenomenon through tailored synthesis. Hence, we set up synthetic methodologies to access a series of thiophene-fused helicenes with a well-defined positioning of the sulfur atoms, which control the occurrence of conducting, linearly conjugated as well as disrupted, cross-conjugated pathways. We describe these synthetic strategies and relate the expected electronic transport through our molecules to three key variables: a) the exo-/endo-topology of the S atom within the ring; b) the parity (odd/even) of the overall number of rings conforming to the helicene; and c) the size of the circuit. This series ranks from [7] to [11] fused rings, having both exo-, endo-, or mixed exo-endo-topology. Comparison of homologous dithiahelicenes with size-tunable highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energies allows us to isolate the key variable of the bond topology from other electronic properties and face the study of QI in helically conjugated molecules. Understanding and tuning the conductance in such molecular solenoids is the main purpose of this work. [ABSTRACT FROM AUTHOR]

We reported a one‐pot photocyclization/ oxidation cascade of N‐aryl acrylamides to afford quinoline‐2‐ones. Thioxanthone was used as a bifunctional energy transfer agent to mediate both photocyclization and generation of singlet oxygen, the latter facilitates the dehydrogenation of dihydroquinoline‐2‐one intermediate. This cascade strategy also supports the 5‐endo‐trig cyclization to synthesize tetrahydrocarbazolones from phenylamino cyclohexenones. [ABSTRACT FROM AUTHOR]

In this contribution, we explored the photocyclization of thioethers to highly substituted dibenzothiophenes (DBT) using solely UV‐light without any need for additives. This cost‐effective, robust and environmentally friendly approach yielded phosphorescent compounds, which were characterized by X‐ray crystallography and state‐of‐the‐art photophysical methods. The resulting DBTs feature ultralong photoluminescence lifetimes and quantum yields close to unity in frozen glassy matrices. The reaction mechanism was elucidated in detail through a combination of quantum chemical calculations and experimental results, providing evidence that triplet states are involved in the cyclization process. Additionally, the photoreaction can also be induced within materials. For this purpose, the precursors were integrated into polymer films or polymer resins suitable for 3D printing. Irradiation of these polymeric objects allows motifs with ultralong phosphorescence to be irreversibly inscribed through the proceeding photocyclization. The in situ photogeneration of DBTs from aromatic thioethers overcomes the observed incompatibilities regarding solubility in polymer resins for 3D printing. [ABSTRACT FROM AUTHOR]

Styrylbenzazoles form a promising yet under‐represented class of photoswitches that can perform a light‐driven E‐Z isomerization of the central alkene double bond without undergoing irreversible photocyclization, typical of the parent stilbene. In this work, we report the synthesis and photochemical study of 23 styrylbenzazole photoswitches. Their thermal stabilities, quantum yields, maximum absorption wavelengths and photostationary state (PSS) distributions can be tuned by changing the benzazole heterocycle and the substitution pattern on the aryl ring. In particular, we found that push‐pull systems show large redshifts of the maximum absorption wavelengths and the highest quantum yields, whereas ortho‐substituted styrylbenzazole photoswitches exhibit the most favorable PSS ratios. Taking advantage of both design principles, we produced 2,6‐dimethyl‐4‐(dimethylamino)‐styrylbenzothiazole, a thermally stable and efficient P‐type photoswitch which displays negative photochromism upon irradiation with visible light up to 470 nm to obtain a near‐quantitative isomerization with a very high quantum yield of 59 %. Furthermore, 4‐hydroxystyrylbenzoxazole was demonstrated to be a pH‐sensitive switch which exhibits a 100 nm redshift upon deprotonation. Ortho‐methylation of its benzothiazole analogue improved the obtained PSS ratio in its deprotonated state from E : Z=53 : 47 to E : Z=18 : 82. We anticipate that this relatively unexplored class of photoswitches will form a valuable expansion of the current family of photoswitches. [ABSTRACT FROM AUTHOR]

Dithienylethene photoswitches with an aromatic π‐linker as the bridge between the two thiophene units are attractive starting materials for developing molecular solar thermal energy (MOST) storage systems, partly because the aromaticity of their ring‐open forms is a favorable feature with regard to the energy‐storage densities of their ring‐closed forms produced by photoinduced electrocyclization (photocyclization) reactions. At the same time, this typically leads to small barriers for their thermal cycloreversion reactions, which are not desirable in this context. Here, we use computational methods to show that this problem can be circumvented with polycyclic heteroaromatic π‐linkers. Specifically, through the tuning of the aromatic character of the individual rings of such a π‐linker (like indole or isoindole), it is shown to be possible to strike a delicate balance between the seemingly contrasting requirements of simultaneously achieving both a high energy‐storage density and a large cycloreversion barrier. Furthermore, this design is also found to provide for a quick and efficient photocyclization reaction, owing to the onset of excited‐state antiaromaticity in the π‐linker upon light absorption of the ring‐open form. Altogether, dithienylethenes with polycyclic heteroaromatic π‐linkers appear to have both thermal and photochemical properties suitable for further development into future MOST systems. [ABSTRACT FROM AUTHOR]

The conductance of a tunneling electron through a π-conjugated molecule may be affected by the presence of different pathways in the orbital structure of the molecule, resulting in the constructive or destructive interference of the molecular wave function. This quantum interference (QI) directly translates into enhancement or suppression of conductance and offers the possibility of controlling this phenomenon through tailored synthesis. Hence, we set up synthetic methodologies to access a series of thiophene-fused helicenes with a well-defined positioning of the sulfur atoms, which control the occurrence of conducting, linearly conjugated as well as disrupted, cross-conjugated pathways. We describe these synthetic strategies and relate the expected electronic transport through our molecules to three key variables: a) the exo-/endo-topology of the S atom within the ring; b) the parity (odd/even) of the overall number of rings conforming to the helicene; and c) the size of the circuit. This series ranks from [7] to [11] fused rings, having both exo-, endo-, or mixed exo-endo-topology. Comparison of homologous dithiahelicenes with size-tunable highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energies allows us to isolate the key variable of the bond topology from other electronic properties and face the study of QI in helically conjugated molecules. Understanding and tuning the conductance in such molecular solenoids is the main purpose of this work.

A novel chiral photoswitch composed of a binaphthyl unit and a hexafluorocyclopentene ring has been synthesized. This chiral photoswitch exhibited thermally reversible photochromism between the binaphthyl and helicenoid forms based on 6π-electrocyclization. The helicity of the binaphthyl moiety was reversed upon stereospecific photocyclization and reverted back during the thermal ring opening. [ABSTRACT FROM AUTHOR]

Photochemical action plots are a powerful tool for mapping photochemical reaction outcomes wavelength‐by‐wavelength. Typically, they map either the depletion of a reactant or the formation of a specific product as a function of wavelength. Herein, we exploit action plots to simultaneously map the formation of several photochemical products from a single chromophore. We demonstrate that the wavelength‐resolved mapping of two reaction products formed during the irradiation of a chalcone species not only shows wavelength dependence – exhibiting the typical strong red‐shift of the photochemical reactivity compared to the absorbance spectrum of the chromophore – but also a strong wavelength selectivity with remarkably different product distributions resulting from different irradiation wavelengths. [ABSTRACT FROM AUTHOR]

The photoreactions of selected styrylpyridine derivatives to the corresponding benzo[c]quinolizinium ions are described. It is shown that these reactions are more efficient in aqueous solution (97–44%) than in organic solvents (78–20% in MeCN). The quinolizinium derivatives bind to DNA by intercalation with binding constants of 6–11 × 104 M−1, as shown by photometric and fluorimetric titrations as well as by CD- and LD-spectroscopic analyses. These ligand–DNA complexes can also be established in situ upon irradiation of the styrylpyridines and formation of the intercalator directly in the presence of DNA. In addition to the DNA-binding properties, the tested benzo[c]quinolizinium derivatives also operate as photosensitizers, which induce DNA damage at relative low concentrations and short irradiation times, even under anaerobic conditions. Investigations of the mechanism of the DNA damage revealed the involvement of intermediate hydroxyl radicals and C-centered radicals. Under aerobic conditions, singlet oxygen only contributes to marginal extent to the DNA damage.

Cyanostilbene is a typical photoresponsive group with multiple photochemical reactions. However, it is still challenging to achieve multiple photochemical reactions and versatility in the same molecular system at one wavelength excitation. The cyanostilbene‐based molecule synthesized in this work can undergo photoisomerization and photocyclization in sequence under continuous illumination at 365 nm in solution. This process is demonstrated by nuclear magnetic resonance, high‐resolution mass spectroscopies, and single crystal X‐ray diffraction. The fluorescence intensity of the solution gradually increases by more than ten times with the extension of the illumination time due to the formation of a photocyclization product with a high fluorescence quantum yield. Based on this interesting phenomenon, the multifunctional applications of this system are presented. This provides a design idea for multifunctional molecules via photochemical reactions. [ABSTRACT FROM AUTHOR]

Diarylethene derivatives are one of the promising compounds for practical applications including optical memory, display, sensor, and photoactuator. In this work, we newly designed and synthesized an inverse type diarylethene derivative bearing sodium carbonate groups at the p‐position of the lateral phenyl ring and investigated the photochromic behavior in the presence and absence of cyclodextrins (CDs) (αCD, βCD, and γCD). Interestingly, only in the presence of βCD, the photocyclization reactivity decreased. From the results of job‐plots, NOESY spectra, and quantum chemical calculations, it was suggested that the distinctive interaction between the diarylethene and βCD leads to the restriction of molecular geometrical change, resulting in the suppression of the photocyclization reactivity. These results provide information on the rational designing of inverse type diarylethenes with advanced properties. [ABSTRACT FROM AUTHOR]

Securines and securamines are cytotoxic alkaloids that contain reactive alkene and heterocyclic residues embedded in skeletons comprising four to six oxidized rings. This structural complexity imparts a rich chemistry to the isolates but has impeded synthetic access to the structures in the nearly three decades since their isolation. We present a flexible route to eight isolates that exemplify the three skeletal classes of metabolites. The route proceeds by the modular assembly of the advanced azides 38 and 49 (13 steps, 6 to 10% yield), sequential oxidative photocyclizations, and late-stage functional group manipulations. With this approach, the targets were obtained in 17 to 19 steps, 12 to 13 purifications, and 0.5 to 3.5% overall yield. The structure of an advanced intermediate was elucidated by microcrystal electron diffraction (MicroED) analysis. The route will support structure-function and target identification studies of the securamines. [ABSTRACT FROM AUTHOR]

The photocyclization of diarylethenes toward polycyclic aromatic hydrocarbons and analogs has been well‐documented. However, stiff‐stilbene was reported to be inactive, and examples of photocyclization‐induced deamination remain unknown. Here, we report that ortho‐(N,N‐dimethylamino)‐stiff‐stilbene (1a) undergoes efficient photocyclization‐induced deamination, forming the dicyclopenta‐fused phenanthrene (DCPP) with good yield (65%) under anaerobic conditions. The relative reactivities of stiff‐stilbenes with different o‐amino substituents (1b–1g) or with an o‐methoxy (1h) group, and those of o‐(N,N‐dimethylamino)stilbenes (2a and 2aMe), provide insights into the substituent and structural effects. [ABSTRACT FROM AUTHOR]

The development of multimode photopatterning systems based on supramolecular coordination complexes (SCCs) is considerably attractive in supramolecular chemistry and materials science, because SCCs can serve as promising platforms for the incorporation of multiple functional building blocks. Herein, we report a light‐responsive liquid‐crystalline metallacycle that is constructed by coordination‐driven self‐assembly. By exploiting its fascinating liquid crystal features, bright emission properties, and facile photocyclization capability, a unique system with spatially‐controlled fluorescence‐resonance energy transfer (FRET) is built through the introduction of a photochromic spiropyran derivative, which led to the realization of the first example of a liquid‐crystalline metallacycle for orthogonal photopatterning in three‐modes, namely holography, fluorescence, and photochromism. [ABSTRACT FROM AUTHOR]

The first facile synthesis of cypripedin (1) was achieved using commercially available 2,3‐dihydroxybenzaldehyde (2) and 5‐bromovanillin (4) via a convergent strategy involving the Mizoroki–Heck reaction and photocyclization as key steps. [ABSTRACT FROM AUTHOR]

Overcrowded bistricyclic aromatic enes (BAEs) have several conformations such as twisted and anti‐folded conformers, and their stereochemistry and chromism have been studied in earnest. In this study, boron‐containing heteromerous BAEs having various tricyclic structures were synthesized and their photophysical properties investigated. Single‐crystal X‐ray analysis revealed that the introduction of a rigid fluorene unit resulted in a twisted conformer, whereas the introduction of flexible units such as thioxanthene and 9,9‐dimethyl‐9,10‐dihydroanthracene units resulted in an anti‐folded conformer. The absorption spectra of the heteromerous BAEs were dependent on the introduced tricyclic structures, suggesting the immense impact of the tricyclic structures on the electronic structures of BAEs. DFT calculations revealed the large effect of the flexibility of the tricyclic structures on the thermodynamic stability of the conformers. In addition, the boron‐containing heteromerous BAEs underwent photocyclization reactions, indicating their potential application as precursors of polyaromatic hydrocarbons and helical aromatic materials. [ABSTRACT FROM AUTHOR]

Photocyclization is demonstrated as a powerful tool for building complicated polycyclic molecules. And efficient photocyclization is competent as an artful strategy to develop photo‐responsive smart materials. Herein, an efficient free radical‐mediated photocyclization for triphenylphosphindole oxide (TPPIO) derivatives to generate tribenzophosphindole oxide (TBPIO) derivatives at ambient condition is reported. The reaction mechanism and substituent effect on photocyclization efficiency are thoroughly investigated. Additionally, photophysical and photochemical properties of TPPIO and TBPIO derivatives are measured for comparison and deeply deciphered by theoretical calculation. TPPIO derivatives own typical aggregation‐induced emission feature but barely generate reactive oxygen species (ROS), while TBPIO derivatives experience aggregation‐caused quenching but show efficient Type I ROS generation capacity. Further, in vitro experiments demonstrate that this photo‐conversion can efficiently occur in situ in living cells to activate photodynamic therapy (PDT) effect to trigger lipid peroxidation with selective fluorescence "light up" in lipid droplet area under continuous irradiation. This work extends the optoelectronically and biologically interesting phosphindole oxide‐containing π‐conjugated systems through an efficient synthetic strategy, provides in‐depth mechanistic descriptions in the aspects of reaction and property, and further presents their great potentials for photoactivated and self‐reported PDT. [ABSTRACT FROM AUTHOR]

A multifaceted study on the effect of various factors on the efficiency of photocyclization of naphthofuran O‐acyl oximes was performed. It showed that without any additives or in the presence of electron acceptors, the reaction occurs by a radical pathway and with low chemoselectivity, while DABCO promotes intramolecular cyclization to give naphthofuroquinolines (NFQs) in 34–87% yields. The iminyl radical formed under UV irradiation in the presence of DABCO due to single electron transfer (SET) and N−O bond cleavage undergoes selective intramolecular homolytic aromatic substitution (HAS) with formation of a new C−N bond. This route to quinoline‐annulated scaffolds is based on the use of DABCO both as an electron transfer agent and a proton acceptor. [ABSTRACT FROM AUTHOR]

Harnessing visible light to trigger (aza and thia) Paternò‐Büchi reaction injects new vitality into [2+2] photocyclization reaction and enable impressive reactivity modes. The popular (aza and thia) Paternò‐Büchi reaction is one of the most efficient ways to synthesize strained four‐membered heterocycles. Recently, visible‐light‐triggered (aza and thia) Paternò‐Büchi reactions have received considerable attentions as this strategy has overcome some long‐standing challenges, and remarkable achievements have been made within this field. Strained four‐membered heterocyclics with favorable properties provide a perfect combination of stable skeletons for pharmaceutical chemistry and reaction intermediates for further transformation. In this review, we highlight the most recent advances in visible‐light‐triggered (aza and thia) Paternò‐Büchi reaction with an emphasis on reaction mechanism and applications. Organization of the review follows a subdivision according to reaction type and substrate classes. [ABSTRACT FROM AUTHOR]

For the first time, we elaborated a method for the synthesis of pyrimidines containing an allomaltol unit. The suggested approach is based on the reaction of 2-(1-(dimethylamino)-3-oxo-3-arylprop-1-en-2-yl)-3-hydroxy-6-methyl-4H-pyran-4-ones with cyanamide. The photochemical behavior of the obtained pyrimidines was investigated. It was shown that for the hydroxy derivatives the main pathway of phototransformation is a 6π-electrocyclization of the 1,3,5-hexatriene system and subsequent [1,9]-H sigmatropic shift leading to dihydrobenzo[h]pyrano[2,3-f]quinazolines. At the same time, for methylated analogues the photoreaction proceeds in two directions resulting in the formation of a mixture of the corresponding dihydrobenzo[h]pyrano[2,3-f]quinazolines and polyaromatic products. The obtained dihydro derivatives are stable compounds and do not undergo aromatization upon further UV irradiation. The structures of two of the dihydrobenzo[h]pyrano[2,3-f]quinazolines were confirmed by X-ray diffraction analysis. Based on the performed studies, a two-stage telescopic method for the synthesis of polyaromatic benzo[h]pyrano[2,3-f]quinazolines including the initial photocyclization of the starting pyrimidines and the final dehydration was proposed.

Abstract Photocyclization is demonstrated as a powerful tool for building complicated polycyclic molecules. And efficient photocyclization is competent as an artful strategy to develop photo‐responsive smart materials. Herein, an efficient free radical‐mediated photocyclization for triphenylphosphindole oxide (TPPIO) derivatives to generate tribenzophosphindole oxide (TBPIO) derivatives at ambient condition is reported. The reaction mechanism and substituent effect on photocyclization efficiency are thoroughly investigated. Additionally, photophysical and photochemical properties of TPPIO and TBPIO derivatives are measured for comparison and deeply deciphered by theoretical calculation. TPPIO derivatives own typical aggregation‐induced emission feature but barely generate reactive oxygen species (ROS), while TBPIO derivatives experience aggregation‐caused quenching but show efficient Type I ROS generation capacity. Further, in vitro experiments demonstrate that this photo‐conversion can efficiently occur in situ in living cells to activate photodynamic therapy (PDT) effect to trigger lipid peroxidation with selective fluorescence “light up” in lipid droplet area under continuous irradiation. This work extends the optoelectronically and biologically interesting phosphindole oxide‐containing π‐conjugated systems through an efficient synthetic strategy, provides in‐depth mechanistic descriptions in the aspects of reaction and property, and further presents their great potentials for photoactivated and self‐reported PDT.

The synthesis, structure, and circularly polarized luminescence (CPL) of two types of shape‐persistent [5]helicenes, hinged by a tethered (−OCH2CH2O−) or untethered (−OCH3) binaphthyl, are reported. The binaphthyl tethering system facilitated an effective Wittig ring‐closure reaction in the synthesis of a macrocyclic precursor, which could be easily converted to the title compound via successive photocyclization. The tethered groups were replaced with untethered −OCH3 groups by treatment with BBr3 followed by methylation. Both compounds exhibited similar spectra, and their longest wavelength absorption band with a low intensity was attributed to the transition from HOMO to LUMO+1. These compounds exhibited CPL with higher dissymmetry factors glum values than unlocked helicenes. [ABSTRACT FROM AUTHOR]

Cyclisations of benzyl ortho-iodoaryl ethers to benzo[c]chromenes can be effected without reagents or catalysts by irradiation with UVC under flow. Reactions proceed via triplet aryl cation generation, 5-exo and 3-exo-cyclisations, and rearomatisation. They have wide scope, are easy to effect and extend to a myriad of related ring systems. [ABSTRACT FROM AUTHOR]

A series of dipeptides 1 was synthesized that at the N-site contained 3-(N-phthalimidoadamantane-1-carboxylic acid and at the C-site different aliphatic or aromatic l- or d-amino acids. The photochemical reaction of dipeptides 1 under acetone-sensitized conditions gave simple decarboxylation products 6, and decarboxylation-induced cyclization products 7, as well as some secondary products 8 and 9 formed by elimination of H2O or ring enlargement, respectively. Molecules 9 undergo secondary photoinduced H-abstractions by the phthalimide chromophore, delivering more complex polycycles 11. The photodecarboxylation-induced cyclization to 7 was observed only with phenylalanine (Phe), proline (Pro), leucine (Leu) and isoleucine (Ile). Contrary to dipeptides with Phe, the cyclization takes place with almost complete racemization at the amino acid chiral center, but diastereoselectively giving only one pair of enantiomers. The conducted investigation is important as it provides the breath and the scope of dipeptide cyclizations activated by phthalimides. [ABSTRACT FROM AUTHOR]

We utilized a cycloaromatization reaction driven by relief of excited state antiaromaticity to photouncage aldehydes and ketones. We developed several synthetic routes towards the synthesis of photocaged carbonyls as allylically substituted 3-(2-(arylethynyl)phenyl)prop-2-en-1-ols. A library of photocaged aryl aldehydes and ketones containing donors and acceptors, as well as several photocaged fragrance aldehydes and the steroid 5α-cholestan- 3 -one, were synthesized and demonstrated photouncaging in good to excellent yields. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with precise designable structures are becoming popular semiconductor materials for photocatalytic applications. In this study, a hydrazone-linked COFs (TFPT-ODH) material was constructed from the reversible polycondensation of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine with oxalohydrazide. Thanks to the bottom-up strategy, the as-prepared TFPT-ODH exhibited satisfactory crystallinity, high thermal and chemical stability. The benefit of the combined effects of narrow band gap and efficient separation of photogenerated carriers, the photofunctional TFPT-ODH further demonstrated outstanding photocatalytic activity, stability, and recyclability in the photocatalytic cyclization reactions of 2-isocyanodiaryl compounds with phenylhydrazine. The photocatalytic mechanism for the photocyclization approach to phenylphenanthridines was proposed based on experimental data and spectrum techniques. Our work also demonstrates application in developing COFs-based photocatalysts for the photocatalytic cyclization of bioactive PAHs derivatives. [ABSTRACT FROM AUTHOR]

Dumbbell-like photochromic dyes were constructed by incorporation of double triangle terthiophene with ethyne or 1,3-butadiene bridge. Regular photochromic behavior was investigated with alternated UV (365 nm) and Visible light (˃ 400 nm) irradiation. However, the different bridge group leads to distinct difference in their photochromic wavelength. For the ethyne bridged triangle terthiophene (DT1), the photochromic wavelength was observed around 500–700 nm (peak value: 605 nm) and the solution turned to red with 365 nm light irradiation. However, the photochromic wavelength was blue shift to 418–550 nm and the solution was turned to light yellow for 1,3-butadiene bridged dye (DT2). Both of the colored solution can be bleached via visible light irradiation. Additionally, the two dyes in THF were emissive with absolute quantum yield (QY) of 0.36/0.40. Along with the photo-induced photocyclization process, the emissive solution can be effectively quenched at photo-stationary sate (Φ = 0.05/0.04). And emission "on-off" cycle could be established based on the UV/visible light irradiation cycle. [ABSTRACT FROM AUTHOR]

Developing a new strategy to realize on‐demand photoreactions with distinguishable signals is highly desirable. Herein, by simply tuning the molecular state, tuned photoreactions with different dynamic signals based on a series of tridentate cyanostilbene molecules (TCS1‐5) are realized. The results show that in the crystalline state, the ordered and densely molecular packing facilitates the successive intermolecular photocycloaddition between adjacent cyanostilbene molecules and causes accumulated stresses within the crystals, which further induces variable photo‐induced mechanical motions such as peeling, bending, twisting, and so on. In the monodispersed solution state, however, the larger distances between TCS1‐5 molecules afford a photo‐induced radical‐assisted intramolecular photocyclization process and give rise to multiple domino photochromic and photofluorochromic behaviors. Based on their distinct yet controllable thermostability and radical colors, photochromic films are fabricated from TCS1@PMMA and TCS1/TFA@PMMA for Morse code and rewritable photopatterning applications, showing excellent photochromism. By coating TCS3 on a piece of plastic bag, the macroscopic mechanical motion is achieved by amplifying the collective molecular motion from the nanoscale up to the macroscopic dimension. The molecular state‐based strategy reveals the regularity between photoreactions and molecular packing and further provides an opportunity to rapidly access controllable photoresponsive systems. [ABSTRACT FROM AUTHOR]

Abstract Tetraphenylethene (TPE), a star building block with promising aggregation‐induced emission, has received much interest. Given that its intramolecular Woodward‐Hoffmann cyclic intermediate instantaneously converts back to the original state within several picoseconds, the essentially photochromic characteristic of TPE is little investigated. Achieving a visible photocyclization of TPE is still an unsolved issue and considered as the bottleneck in the further advancement of applications. We report a strategy of attaching carbonate ester onto the TPE skeleton (TPE‐4C) to enhance TPE photocyclization stability. As demonstrated, the incorporated cholesteryloxycarbonyloxy substituents in TPE‐4C can increase the energy barrier for cycloreversion, thereby exhibiting extremely thermal stability of photocyclic intermediate upon UV irradiation, prolonging its lifetime from 63 picoseconds to 46 s by 7.2 × 1011‐fold. The photoinduced cyclization of TPE‐4C could be monitored with naked eyes, and the photocyclization/cycloreversion is achieved by turning on/off UV light along with a relative fatigue resistance. Encapsulation of TPE‐4C into the liquid crystal can induce a striking phase transformation (achiral↔chiral), which can be applicable to encode optical information. Employing carbonate ester into the TPE unit plays a vital role in enhancing the unprecedented TPE photocyclization stability, providing a toolbox to allow TPE‐based photocyclization to be visually monitored.

A photochemical cyclization of F‐tagged, o‐alkynylated N‐alkylamides to indoles catalyzed by [Ir(dF(CF3)ppy)2(dtbpy)]PF6 is presented. This straightforward and efficient reaction involves an intramolecular rearrangement due to the presence of an electron withdrawing group in the acyl moiety and is the first example of photochemically induced 1,3‐acyl shift in the cyclization towards 3‐acylindoles. A four‐step reaction sequence including the photoreaction as a key step to the desired indoles has been developed and optimized. The compatibility of differently substituted F‐tagged precursors with the photocyclization step was investigated and the robustness of this step towards modifications could be shown. In total, 16 so far unknown derivatives with diverse modifications in positions N1 and C2, bearing a pentadecafluorooctanoyl moiety as F‐tag, were synthesized in very good yields and fully characterized. [ABSTRACT FROM AUTHOR]

In this work, the design and synthesis of a series of photochromic gemini diarylethene-based ionic liquids (GDILs) with different cationic motifs is reported. Several synthetic pathways were optimized for the formation of cationic GDILs with chloride as the counterion. The different cationic motifs were achieved through the N-alkylation of the photochromic organic core unit with different tertiary amines, including different aromatic amines such as imidazole derivatives and pyridinium, and other non-aromatic amines. These novel salts present surprising water solubility with unexplored photochromic features that broaden their known applications. The covalent attachment of the different side groups dictates their water solubility and differences upon photocyclization. The physicochemical properties of GDILs in aqueous and in imidazolium-based ionic liquid (IL) solutions were investigated. Upon irradiation with ultraviolet (UV) light, we have observed changes in the physico-chemical properties of distinct solutions containing these GDILs, at very low concentrations. More specifically, in aqueous solution, the overall conductivity increased with the time of UV photoirradiation. In contrast, in IL solution, these photoinducible changes are dependent on the type of ionic liquid used. These compounds can improve non-ionic and ionic liquids' solutions since we can change their properties, such as conductivity, viscosity or ionicity, only by UV photoirradiation. The electronic and conformational changes associated with these innovative stimuli GDILs may open new opportunities for their use as photoswitchable materials. [ABSTRACT FROM AUTHOR]

Enzymes facilitate chemical conversions through the collective activity of aggregated components, but the marriage of aggregation‐induced emission (AIE) with molecular containers to emulate enzymatic conversion remains challenging. Herein, we report a new approach to construct a PtII‐based octahedral cage with AIE characteristics for the photocyclization of alkynylaniline by restricting the rotation of the pendant phenyl rings peripheral to the PtII corner. With the presence of water, the C−H⋅⋅⋅π interactions involving the triphenylphosphine fragments resulted in aggregation of the molecular cages into spherical particles and significantly enhanced the PtII‐based luminescence. The kinetically inert Pt‐NP chelator, with highly differentiated redox potentials in the ground and excited states, and the efficient coordination activation of the platinum corner facilitated excellent catalysis of the photocyclization of alkynylaniline. The enzymatic kinetics and the advantages of binding and activating substrates in an aqueous medium provide a new avenue to develop mimics for efficient photosynthesis. [ABSTRACT FROM AUTHOR]

Because of the ultrafast C=C bond torsion and electrocyclic reaction in the excited state, cis‐stilbenes are generally nonfluorescent (Φf <10−4) in common solvents at ambient temperature. The known examples of highly fluorescent cis‐stilbenes are limited to those with the C=C configuration structurally locked. Herein we report a novel cis‐stiff‐stilbene c‐2 a that displays a high fluorescence quantum efficiency up to 0.47 in acetonitrile (MeCN) without sacrificing the photoisomerization ability. Through comparison with the corresponding aminostilbene c‐1 and positional isomer c‐2 b, the fluorescence turn‐on for c‐2 a takes root in two structural origins: namely, a rigid stilbene backbone that suppresses the cis→dihydrophenanthrene (DHP) photocyclization and a non‐twisted meta‐N,N‐dimethylamino (DMA) substituent that slows down the cis→trans photoisomerization. The corresponding trans isomers t‐1, t‐2 a, and t‐2 b are also investigated to gain insights into the meta‐DMA effect in stiff‐stilbene. [ABSTRACT FROM AUTHOR]

In this research, the synthesis, photochemistry, and computational study of new cis- and trans-isomers of amino-thienostilbenes is performed to test the efficiency of their production and acid resistance, and to investigate their electronic structure, photoreactivity, photophysical characteristics, and potential biological activity. The electronic structure and conformations of synthesized thienostilbene amines and their photocyclization products are examined computationally, along with molecular modeling of amines possessing two thiophene rings that showed inhibitory potential toward cholinesterases. New amino-styryl thiophenes, with favorable photophysical properties and proven acid resistance, represent model compounds for their water-soluble ammonium salts as potential styryl optical dyes. The comparison with organic dyes possessing a trans-aminostilbene subunit as the scaffold shows that the newly synthesized trans-aminostilbenes have very similar absorbance wavelengths. Furthermore, their functionalized cis-isomers and photocyclization products are good candidates for cholinesterase inhibitors because of the structural similarity of the molecular skeleton to some already proven bioactive derivatives. [ABSTRACT FROM AUTHOR]

Blue-LED light or direct sunlight induces cyclization in tryptamine-quinone hybrid compounds. Formation of a C-C bond between the C-2 atom of the indole and the bromo-naphthoquinone takes place in chloroform solution in air without the need for a photocatalyst. The reaction allows the presence of a bromine atom on the indole ring which can be used for subsequent cross coupling reactions. On the other hand, the bromine atom on the naphthoquinone is strictly necessary for the cyclization to occur. The cyclic products of these reactions are blue pigments with broad absorption in the visible region. [ABSTRACT FROM AUTHOR]

Thienodipyrimidine-2,4,5,7-tetra(thi)ones were prepared by one-pot photocyclization from barbituric acid derivatives. The structures of these tricyclic molecules with multiple (thio)carbonyl groups were determined by NMR and single-crystal X-ray diffraction analysis, and the electrochemical properties were studied by cyclic voltammetry and DFT calculations. The solid-state structures of these molecules feature dipolar C=S (or C=O), chalcogen-bonding, and π-stacking interactions. The presence of two adjacent thiocarbonyl groups allows for a two-center three-electron (2c/3e) interaction upon oxidation, significantly lowering the oxidation potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxidative photocyclization of 4,5-diphenyl-substituted imidazoles led to 9,10-phenanthroimidazoles. • The intermediate 4a,4b-dihydrophenanthrene derivatives are very unstable species. • The revised structures of photoproducts, reported in [ J. Photochem. Photobiolog. A 2024 , 454 , 115750]. In the recent paper of S. Pu and coworkers (J. Photochem. Photobiolog. A 2024 , 454 , 115750), three novel 4,5-diphenylimidazole derivatives were studied. The fluorescent properties of these compounds changed drastically upon UV irradiation, as a result of irreversible phototransformation. As products of this reaction, the authors proposed questionable 7a,7b-dihydrophenanthro[9,10-d]imidazoles with completely non-aromatic core. Based on the literature data as well as author's results, we suggest more believable structures of photoproducts, formed via well-known oxidative photocyclization (Mallory reaction) or photocyclization / H-migration. [ABSTRACT FROM AUTHOR]

[Display omitted] Two novel aromatic thiophene-containing annulated compounds, viz. 2-methoxy[ b ]naphtho[2,1- d ]thiophene and 1,3-dimethoxy[ b ]naphtho[2,1- d ]thiophene, were synthesized via the Mallory-type photocyclization. Their optical, redox and photophysical properties have been studied along with phosphorescence spectra and lifetimes at 77 K. The first compound exhibited much higher charge mobility in thin films than the second one suggesting the former being prospective for molecular electronics applications [ABSTRACT FROM AUTHOR]

A new and efficient method for the synthesis of 6-organyl-5-(arylselanyl)benzo[h]quinolines via visible light-promoted intramolecular ortho-cyclization of 2-aryl-3-(organylethynyl)pyridines has been achieved. The reaction was promoted by radical organochalcogen species generated in situ using diorganyl dichalcogenides, indium chloride as a green Lewis acid and acetonitrile under an argon atmosphere. The protocol showed high regioselectivity and allowed the synthesis of eleven benzo[h]quinoline derivatives in low to good yields. Also, compound 5a demonstrated in vitro antioxidant activity as well as in silico appropriate pharmacodynamic and pharmacokinetic profiles, suggesting that this compound may have promising therapeutic potential. [ABSTRACT FROM AUTHOR]

In this study, the conversion of self-assembled structures into continuous polymeric structures by linking the self-assembled molecules using the [2 + 2]-cycloaddition reaction was investigated. Synthesized bio-inspired thymine-based bolaamphiphilic molecules were designed to force the interactions between two molecules to engage two thymines in their self-assembled structure to undergo a cycloaddition reaction. Thymine-based bolaamphiphilic molecules were designed and synthesized using different phenylene spacers based on aromatic substituents (ortho-) (meta-) (para-). The formed self-assembled structures from these molecules were characterized and compared using molecular mechanical simulations. Simulations were performed to discuss the relationship between the inter- and intramolecular cycloaddition sensitivity to different substituents. This study provides a strategy for creating higher molecular weight linear polymers by controlling the photocyclization sites within the self-assembly by spacers between thymines. An intermolecular [2 + 2] cycloaddition reaction of thymine-based bolaamphiphilic molecules proceeded within the self-assembled nano-ribbon-like structure to form the continuous covalent structure. [ABSTRACT FROM AUTHOR]

The synthesis of 2‐azetidinones (β‐lactams) from simple acrylamide starting materials by visible‐light‐mediated energy transfer catalysis is reported. The reaction features a C(sp3)−H functionalization via a variation of the Norrish–Yang photocyclization involving a carbon‐to‐carbon 1,5‐hydrogen atom transfer (supported by deuterium labelling and DFT calculations) and can be used for the construction of a diverse range of β‐lactam products. [ABSTRACT FROM AUTHOR]

Supramolecular assembly‐induced emission enhancement (SAIEE) systems have been proved to be a highly efficient approach for the fabrication of luminescent nanoparticles with uniform morphology. Herein, fluorescent supramolecular vesicles are constructed from tetraphenylethene‐based cyano‐alkane tetramer (TPE‐(CN)4) and pincer‐like hosts containing two pillar[5]arene units (B‐(TAP[5]A)2) through a synergistic effect of host–guest interactions and hydrophobic interactions. Notably, the emission intensity of supramolecular vesicles can be remarkably enhanced with quantum yield determined to be 37.69%, whereas that of TPE‐(CN)4 is only 18.93% in mixture solvent. Furthermore, the supramolecular vesicles can retard the photocyclization reaction of TPE‐(CN)4 under UV light and exhibit considerable emission intensity at high temperature. Enthused by the above results, artificial light‐harvesting systems with high antenna effect of 18.7 are facilely established by introducing cyano‐vinyl derivatives (CV‐CN) as donor, demonstrating the adjustable emission wavelength through Förster resonance energy transfer in the present SAIEE systems. Taking advantage of the tunable emission colors, fluorescent ink based on supramolecular vesicles is successfully prepared, setting the basis for potential application in security painting. As a proof‐of‐concept study, the pincer‐like host facilitates the optical performance of chromophores with aggregation‐induced emission feature, and unlocks more possibilities for the establishment of SAIEE systems in aqueous. [ABSTRACT FROM AUTHOR]

Doping main‐group elements has become a unique strategy to fine‐tune optoelectronic properties of organic π‐conjugated molecules. Herein, we report the first example of diazaphosphinine based polycyclic hydrocarbons (DP‐PAHs) via facile synthetic protocols. Synthesis of diazaphosphinine heterocycles harnesses mild and efficient P−N chemistry. The heterocycles readily undergo photocyclizations by using only oxidants. The photocyclization protocol is applicable to the heterocycles with various P‐centers. We successfully extended the protocols in extended DP‐PAHs with 13‐fused aromatic rings. Further adjusting P‐chemistry allows to efficiently fine‐tune the singlet and triplet emission characteristics. More importantly, single‐molecule white‐light‐emitting character was achieved via the balanced singlet and triplet emission of DP‐PAH. Therefore, this work opens up new horizons in the area of organic π‐conjugated materials. [ABSTRACT FROM AUTHOR]

The photochemical 6π‐electrocyclization of diarylethenes (DAE), 2‐vinylbiaryls (VBA) and their derivatives is widely used in organic synthesis. Combination of these motifs in one molecule opens the issue of selectivity of the photochemical reaction. We have found that upon UV irradiation, 3‐(1,2‐diarylvinyl)‐2‐arylimidazo[1,2‐a]pyridines comprising both DAE and VBA moieties form products of VBA cyclization followed by oxidation. The selectivity of the process was rationalized by DFT calculations. The presented reaction gave access to highly fluorescent 5,6‐diarylnaphtho[1′,2′:4,5]imidazo[1,2‐a]pyridine derivatives. [ABSTRACT FROM AUTHOR]

A synthetic approach to grandisol is described. The route to the cyclobutane core relies on an efficient intramolecular [2+2] cyclo-addition that establishes the required cis -ring fusion at the adjacent side chains of the cyclobutane ring. Using a new two-step lithium/halide homologation procedure, norgrandisol was efficiently converted into grandisol. This new approach enables the synthesis of grandisol in five steps from commercially available starting material in 22% overall yield. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three new optical responsive molecules AT-TPIo , AT-DPIo , and AT-HDPIo have been successfully synthesized. • All of these compounds exhibited remarkable invisible photochromism accompanied by pronounced "turn-off" fluorescence. • AT-TPIo demonstrated high selectivity and sensitivity as a sensor for the detection of I− ions. Three novel diarylethene fluorescent molecules based on a thiophene-imidazole core have been successfully synthesized. Their photophysical properties, including photocyclization and ions response characteristics, as well as quantum chemical calculations were systematically investigated. All compounds exhibited significant invisible photochromism upon photocyclization, resulting in remarkable fluorescence "turn-off" properties. This phenomenon can be attributed to photoisomerization, specifically the transition from the open-ring isomer to the closed-ring isomer during this process, which was confirmed by 1H NMR data analysis. Moreover, AT-DPIo demonstrated high selectivity toward I− with pronounced changes in absorption from colorless to yellow and fluorescence from bright yellow to dark, enabling a limit of detection for I− at 9.75 × 10−7 mol L−1. These exceptional sensing properties make it suitable for rapid "naked-eye" detection of I− using test strips. [ABSTRACT FROM AUTHOR]