Activation of Anthraquinone's Electrophilicity by Light for a Dynamic C-O Bond.

Coupling of photoswitching with dynamic covalent chemistry enables control of the formation and cleavage of covalent bonds by light irradiation. peri-Aryloxyanthraquinones feature an exclusive ability to switch electrophilicity by interconversion between para- and ana-quinone isomers, which was used for the first time for the implementation of a dynamic C-O bond. Photogenerated ana-isomers undergo a concerted oxa-Michael addition of phenols to give hitherto unknown 4-hydroxy-10,10-diaryloxyanthracen-9-ones. These species were found to be in equilibrium with the corresponding ana-quinones, thus forming a dynamic covalent system of a new type. Withdrawal of the colored ana-quinones from the equilibria by visible light irradiation resulted in two para-quinones with "locked" aryloxy groups.

Revisiting Peri-Aryloxyquinones: From a Forgotten Photochromic System to a Promising Tool for Emerging Applications.

Emerging applications of photochromic compounds demand new molecular designs that can be inspired by some long-known yet currently forgotten classes of photoswitches. In the present review, we remind the community about Peri-AryloxyQuinones (PAQs) and their unique photoswitching behavior originally discovered more than 50 years ago. At the heart of this phenomenon is the light-induced migration of an aromatic moiety (arylotropy) in peri-aryloxy-substituted quinones resulting in ana-quinones. PAQs feature absorbance of both isomers in the visible spectral region, photochromism in the amorphous and crystalline state, and thermal stability of the photogenerated ana-isomer. Particularly noticeable is the high sensitivity of the ana-isomer towards nucleophiles in solution. In addition to the mechanism of molecular photochromism and the underlaying structure-switch relationships, we analyze potential applications and prospects of aryloxyquinones in optically switchable materials and devices. Due to their ability to efficiently photoswitch in the solid state, PAQs are indeed attractive candidates for such materials and devices, including electronics (optically controllable circuits, switches, transistors, memories, and displays), porous crystalline materials, crystalline actuators, photoactivated sensors, and many more. This review is intended to serve as a guide for researchers who wish to use photoswitchable PAQs in the development of new photocontrollable materials, devices, and processes.

2,3-Diarylmaleate salts as a versatile class of diarylethenes with a full spectrum of photoactivity in water.

There is incessant interest in the transfer of common chemical processes from organic solvents to water, which is vital for the development of bioinspired and green chemical technologies. Diarylethenes feature a rich photochemistry, including both irreversible and reversible reactions that are in demand in organic synthesis, materials chemistry, and photopharmacology. Herein, we introduce the first versatile class of diarylethenes, namely, potassium 2,3-diarylmaleates (DAMs), that show excellent solubility in water. DAMs obtained from highly available precursors feature a full spectrum of photoactivity in water and undergo irreversible reactions (oxidative cyclization or rearrangement) or reversible photocyclization (switching), depending on their structure. This finding paves a way towards wider application of diarylethenes in photopharmacology and bioinspired technologies that require aqueous media for photochemical reactions.

White paper on psychodermatology in Europe: A position paper from the EADV Psychodermatology Task Force and the European Society for Dermatology and Psychiatry (ESDaP).

Psychodermatology is a subspecialty of dermatology that is of increasing interest to dermatologists and patients. The case for the provision of at least regional psychodermatology services across Europe is robust. Psychodermatology services have been shown to have better, quicker and more cost-efficient clinical outcomes for patients with psychodermatological conditions. Despite this, psychodermatology services are not uniformly available across Europe. In fact many countries have yet to establish dedicated psychodermatology services. In other countries psychodermatology services are in development. Even in countries where psychodermatolgy units have been established, the services are not available across the whole country. This is especially true for the provision of paediatric psychodermatology services. Also whilst most states across Europe are keen to develop psychodermatology services, the rate at which this development is being implemented is very slow. Our paper maps the current provision of psychodermatology services across Europe and indicates that there is still very much more work to be done in order to develop the comprehensive psychodermatology services across Europe, which are so crucial for our patients.

Light-Induced Dyotropic Rearrangement of Diarylethenes: Scope, Mechanism, and Prospects.

Irreversible two-photon photorearrangement of 1,2-diarylethenes is a unique process providing access to complex 2a1 ,5a-dihydro-5,6-dithiaacenaphthylene (DDA) heterocyclic core. This reaction was serendipitously discovered during studies on photoswitchable diarylethenes and was initially considered as a highly undesired process. However, in recent years, it has been recognized as an efficient photochemical reaction, interesting by itself and as a promising synthetic method for the synthesis of challenging molecules. Herein, we discuss the state-of-the-art in studies on this notable process.

Perceived Stigmatization among Dermatological Outpatients Compared with Controls: An Observational Multicentre Study in 17 European Countries.

Perceived stigmatization places a large psychosocial burden on patients with some skin conditions. Little is known about the experience of stigmatization across a wide range of skin diseases. This observational cross-sectional study aimed to quantify perceived stigmatization and identify its predictors among patients with a broad spectrum of skin diseases across 17 European countries. Self-report questionnaires assessing perceived stigmatization and its potential predictors were completed by 5,487 dermatology outpatients and 2,808 skin-healthy controls. Dermatological diagnosis, severity, and comorbidity were clinician-assessed. Patients experienced higher levels of perceived stigmatization than controls (p < 0.001, d = 0.26); patients with psoriasis, atopic dermatitis, alopecia, and bullous disorders were particularly affected. Multivariate regression analyses showed that perceived stigmatization was related to sociodemographic (lower age, male sex, being single), general health-related (higher body mass index, lower overall health), disease-related (higher clinician-assessed disease severity, presence of itch, longer disease duration), and psychological (greater distress, presence of suicidal ideation, greater body dysmorphic concerns, lower appearance satisfaction) variables. To conclude, perceived stigmatization is common in patients with skin diseases. Factors have been identified that will help clinicians and policymakers to target vulnerable patient groups, offer adequate patient management, and to ultimately develop evidence-based interventions.

Multifunctional fluorescent diarylethene: time-resolved study of photochemistry.

A study of luminescence and photochromic properties of (E)-2,3-bis(2,5-dimethylthiophen-3-yl)-5-(4-(pyrrolidin-1-yl)benzylidene)cyclopent-2-en-1-one, which is a diarylethene with a push-pull system between carbonyl and dimethylamino groups, was performed using time-resolved methods. The intramolecular charge transfer (ICT) process as well as 6π-electrocyclization and E-/Z-isomerization contribute to the complex light-induced properties of this molecule. Formation of unexpected short-lived intermediates was detected in the time range from 100 fs to 100 µs. A model based on two processes (additional photocyclization and interconversion between conformers) was proposed to rationalize this result. The key intermediates existing in the picosecond time domain are so-called precursors, which are proposed for both parallel (p) and anti-parallel (ap) isomers of the open form. In general, fast light-induced processes for the fluorescent diarylcyclopentenones are much more complicated than for the parent cyclopentenone-based DAE.

Redirecting of Charge Transfer Enables the Control of the Photoactivity of Terarylenes.

Photoinduced charge transfer affects the efficiency and selectivity of photochemical reactions. Incorporation of donating groups into the isoquinolinium core allowed us to overcome the photochemical inactivity of the corresponding dithienyl-substituted terarylenes, presumably by redirecting the charge transfer within the molecule, and gave access to a new family of thermally reversible photoswitches.

Body dysmorphia in common skin diseases: results of an observational, cross-sectional multicentre study among dermatological outpatients in 17 European countries.

BACKGROUND: Body dysmorphic disorder (BDD) is a common psychiatric disorder associated with high costs for healthcare systems as patients may repeatedly ask for different, often not effective, interventions. BDD symptoms are more prevalent in patients with dermatological conditions than in the general population, but there are no large sample studies comparing the prevalence of BDD symptoms between patients with dermatological conditions and healthy skin controls. OBJECTIVES: To compare the prevalence of BDD symptoms between patients with different dermatological conditions and healthy skin controls and to describe sociodemographic, physical and psychological factors associated with BDD symptoms to identify patients who may have a particularly high chance of having this condition. METHODS: This observational, cross-sectional, comparative multicentre study included 8295 participants: 5487 consecutive patients with different skin diseases (56% female) recruited among dermatological outpatients at 22 clinics in 17 European countries, and 2808 healthy skin controls (66% female). BDD symptoms were assessed by the Dysmorphic Concern Questionnaire. Sociodemographic data and information on psychological factors and physical conditions were collected. Each patient was given a dermatological diagnosis according to ICD-10 by a dermatologist. The study was registered with number DRKS00012745. RESULTS: The average participation rate of invited dermatological patients was 82.4% across all centres. BDD symptoms were five times more prevalent in patients with dermatological conditions than in healthy skin controls (10.5% vs. 2.1%). Patients with hyperhidrosis, alopecia and vitiligo had a more than 11-fold increased chance (adjusted Odds Ratio (OR) > 11) of having BDD symptoms compared with healthy skin controls, and patients with atopic dermatitis, psoriasis, acne, hidradenitis suppurativa, prurigo and bullous diseases had a more than sixfold increased chance (adjusted OR > 6) of having BDD symptoms. Using a logistic regression model, BDD symptoms were significantly related to lower age, female sex, higher psychological stress and feelings of stigmatization. CONCLUSIONS: Clinical BDD symptoms are significantly associated with common dermatological diseases. As such symptoms are associated with higher levels of psychological distress and multiple unhelpful consultations, general practitioners and dermatologists should consider BDD and refer patients when identified to an appropriate service for BDD screening and management.

Photocyclization of Diarylethenes: The Effect of Electron and Proton Acceptors as Additives.

The effect of electron and proton acceptors on the photocyclization of diarylethenes has been studied. Without any additives, the deprotonation reaction is predominant, although other processes, including the sigmatropic shift, are not excluded. A deuterium exchange experiment has shown that a strong base (DABCO) facilitates the deprotonation reaction, thereby limiting the sigmatropic shift. In the presence of an oxidizing agent or additional sources of radicals (O2, I2, TEMPO), the processes of deprotonation and rearrangement (H-shift) are practically not observed, and the reaction proceeds along a radical pathway with the formation of phenanthrene or its heterocyclic analogue.

Azulene as an ingredient for visible-light- and stimuli-responsive photoswitches.

The azulene molecule features a unique combination of optical, luminescence, and stimuli-responsive properties. This makes the azulene motif a promising functional group to be introduced in photoswitches. Recent challenges in the field of photochromic compounds require the development of new approaches to molecules that are switched by visible light (400-760 nm), are proton responsive and have advanced luminescent properties. Merging azulene with photoswitches opens prospects for fulfilling these requirements. Herein, we highlight recent results on the application of this hydrocarbon motif in various photochromic systems, such as stilbenes, diarylethenes, and azobenzenes.

Photocontrollable Modulation of Frontier Molecular Orbital Energy Levels of Cyclopentenone-Based Diarylethenes.

Photoswitchable diarylethenes provide a unique opportunity to optically modulate frontier molecular orbital energy levels, thereby opening an avenue for the design of electronic devices such as photocontrollable organic field-effect transistors (OFETs). In the present work, the absolute position of the frontier orbital levels of nonsymmetrical diarylethenes based on a cyclopentenone bridge has been studied using cyclic voltammetry and density functional theory (DFT) calculations. It has been shown that varying heteroaromatic substituents make it possible to change the absolute positions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of both diarylethene photoisomers. The data obtained are used to refine the operation mechanism of the previously developed OFET devices, employing the cyclopentenone-derived diarylethenes at the dielectric/semiconductor interface.

Chronic Nodular Prurigo: A European Cross-sectional Study of Patient Perspectives on Therapeutic Goals and Satisfaction.

Chronic nodular prurigo is characterized by recalcitrant itch. Patient perspectives on therapeutic goals, satisfaction with therapy and efficacy of therapeutic regimens for this condition are unknown. This questionnaire study examined these issues in 406 patients with chronic nodular prurigo from 15 European dermatological centres. Improvements in itch, skin lesions and sleep were the most important goals. Emollients, topical corticosteroids and antihistamines were the most frequently used treatments, while a minority of patients were prescribed potent medications, such as systemic immunosuppressants and gabapentinoids. Most patients were not satisfied with their previous therapy (56.8%), while 9.8% did not receive any therapy despite having active disease. A substantial number of respondents (28.7%) considered none of the therapeutic options effective. Although chronic nodular prurigo is a severe disease, most patients were not treated with potent systemic drugs, which may contribute to the high levels of dissatisfaction and disbelief in available therapies. Specific guidelines for chronic nodular prurigo and the development of novel therapies are necessary to improve care.

Light-Sensitive Material Structure-Electrical Performance Relationship for Optical Memory Transistors Incorporating Photochromic Dihetarylethenes.

Photoswitchable organic field-effect transistors (OFETs) with embedded photochromic materials are considered as a promising platform for development of organic optical memory devices. Unfortunately, the operational mechanism of these devices and guidelines for selection of light-sensitive materials are still poorly explored. In the present work, a series of photochromic dihetarylethenes with a cyclopentenone bridge moiety were investigated as a dielectric/semiconductor interlayer in the structure of photoswitchable OFETs. It was shown that the electrical performance and stability of the devices can be tuned by variation of the substituents in the structure of the photochromic material. In particular, it was found that dihetarylethenes with donor substituents demonstrated the best light-induced switching effects (wider memory windows and higher switching coefficients) in the devices. The operation mechanism of the light-triggered memory devices was proposed based on the differential in situ Fourier transform infrared (FTIR) spectroscopy data and regression analysis of the threshold voltage-programming time experimental dependencies. The established relationships will facilitate further rational design of new photochromic materials, thus paving a way to fast and durable organic optical memories and memory transistors (memristors).

Switching the Mallory Reaction to Synthesis of Naphthalenes, Benzannulated Heterocycles, and Their Derivatives.

This review analyzes the new life of a long-known reaction, the photocyclization of diarylethenes, which became a classical tool for the synthesis of phenanthrenes and their heterocyclic analogues (Mallory reaction). It has been shown in recent years that certain diarylethenes undergo photorearrangement to naphthalenes, benzannulated heterocycles, or related products with bicyclic unit. Herein, I analyze how the Mallory reaction path can be altered to obtain bicyclic rather than tricyclic products. The mechanistic aspects and scope of the reaction are discussed.

Reversible Shifting of a Chemical Equilibrium by Light: The Case of Keto-Enol Tautomerism of a ß-Ketoester.

Manipulating the equilibrium between a ketone and an enol by light opens up ample opportunities in material chemistry and photopharmacology. By incorporating ß-ketoester into the ethene bridge of a photoactive diarylethene, we achieved reversible light-induced tautomerization to give thermally stable enol. In a pristine state, the tautomeric equilibrium is almost completely shifted toward the ketone. Photocyclization of diarylethene results in a new equilibrium containing a significant fraction of the enol tautomer.

Post-Modification of the Ethene Bridge in the Rational Design of Photochromic Diarylethenes.

Fine-tuning of the molecular structure of organic bistable compounds to improve their photochromic performance or to introduce additional functions remains an important issue in the development of photoresponsive materials. Diarylethenes bearing heterocyclic moieties belong to the most intensively studied class of organic photochromes due to their excellent photochemical properties. A huge number of diarylethenes have been synthesized so far. Analysis of the literature data shows that there are very worthy examples of diarylethenes developed by the Irie and Feringa groups, which can be the common starting material for a number of diarylethenes functionalized in hetaryl moieties. We refer to these structures as photochromic diarylethene precursors. These diarylethenes have proved to be very useful in the construction of functional molecules with desired properties. On the other hand, in our groups, we have elaborated on diarylethene precursors with modifiable ethene bridges. In this review, we have collected examples of such structures and their chemical modifications, leading to the improvement or fine-tuning of photochromic switching.

Itch and Mental Health in Dermatological Patients across Europe: A Cross-Sectional Study in 13 Countries.

Itch is a highly prevalent and multidimensional symptom. We aimed to analyze the association between itch and mental health in dermatological patients. This multicenter study is observational and cross-sectional and was conducted in dermatological clinics across 13 European countries. A total of 3,530 patients and 1,094 healthy controls were included. Patients were examined clinically. Outcome measures were itch (presence, chronicity, and intensity), the Hospital Anxiety and Depression Scale, EQ-5D visual analogue scale, sociodemographics, suicidal ideation, and stress (negative life events and economic difficulties). Ethical approval was obtained. Results showed significant association between the presence of itch in patients and clinical depression (odds ratio, 1.53; 95% confidence interval, 1.15-2.02), suicidal ideation (odds ratio, 1.27; 95% confidence interval, 1.01-1.60), and economic difficulties (odds ratio, 1.24; 95% confidence interval, 1.10-1.50). The mean score of reported generic health status assessed by the EQ-5D visual analogue scale was 65.9 (standard deviation = 20.1) in patients with itch, compared with 74.7 (standard deviation = 18.0) in patients without itch (P < 0.001) and 74.9 (standard deviation = 15.7) in controls with itch compared with 82.9 (standard deviation = 15.6) in controls without itch (P < 0.001). Itch contributes substantially to the psychological disease burden in dermatological patients, and the management of patients should include access to multidisciplinary care.

Photoswitching off the Antiproliferative Activity of Combretastatin A-4 Analogues.

The photostability and antiproliferative activity of combretastatin A-4 (CA-4) analogues against human epidermoid carcinoma cells A-431 were studied. For the first time, it was shown that UV or sunlight irradiation of furanone analogues of CA-4 results in a photorearrangement giving products with relatively low antiproliferative activity. The observed ability of this series CA-4 to the photodegradation can be used for the design of a new class of drug candidates with high selectivity to cancer cells.