Urea-Comprising Single Core Diketopyrrolopyrrole Derivatives: Exploring the Synthesis, Self-Assembly and Charge Transport Properties.

Supramolecular electronics exploits the distinctive features stemming from noncovalent interactions, guiding the self-assembly of molecules to craft materials endowed with customized electronic functionalities. Hydrogen-bonded materials, characterized by their capacity to establish dynamic and stable networks, introduce an extra dimension to the development of supramolecular electronic systems. This study presents a comparative analysis of two remarkably small semiconductors utilizing diketopyrrolopyrrole functionalized with urea units as hydrogen-bonding motifs, strategically positioned at opposing ends of the conjugated core. We show how the subtle distinction in functionalization not only influences morphology and self-assembly dynamics via hydrogen-bonding and π-π stacking formation, but also holds significant consequences for ultimate charge transport properties. Our observations into the interplay of noncovalent interactions provide valuable insights and strategic pathways for the design of novel materials with enhanced electronic characteristics.

Daisy chain architectures: from discrete molecular entities to polymer materials.

Daisy chain architectures, made by the self-complementary threading of an axle covalently linked to a macrocycle, represent a particularly intriguing family of supramolecular and mechanically interlocked (macro)molecules. In this review, we discuss their recent history, their modular chemical structures, and the various synthetic strategies to access them. We also detail how their internal sliding motions can be controlled and how their integration within polymers can amplify that motions up to the macroscopic scale. This overview of the literature demonstrates that the peculiar structure and dynamics of daisy chains have already strongly influenced the research on artificial molecular machines, with the potential to be implemented from nanometric switchable devices to mechanically active soft-matter materials.

From Molecular Machines to Stimuli-Responsive Materials.

Artificial molecular machines are able to produce and exploit precise nanoscale actuations in response to chemical or physical triggers. Recent scientific efforts have been devoted to the integration, orientation, and interfacing of large assemblies of molecular machines in order to harness their collective actuations at larger length scale and up to the generation of macroscopic motions. Making use of such "hierarchical mechanics" represents a fundamentally new approach for the conception of stimuli-responsive materials. Furthermore, because some molecular machines can function as molecular motors-which are capable of cycling a unidirectional motion out of thermodynamic equilibrium and progressively increasing the work delivered to their environment-one can expect unique opportunities to design new kinds of mechanically active materials and devices capable of autonomous behavior when supplied by an external source of energy. Recently reported achievements are summarized, including the integration of molecular machines at surfaces and interfaces, in 3D self-assembled materials, as well as in liquid crystals and polymer materials. Their detailed functioning principles as well as their functional properties are discussed along with their potential applications in various domains such as sensing, drug delivery, electronics, optics, plasmonics, and mechanics.

Susceptibility of Enterococcus faecalis and Propionibacterium acnes to antimicrobial photodynamic therapy.

Bacterial resistance to available antibiotics nowadays is a global threat leading researchers around the world to study new treatment modalities for infections. Antimicrobial photodynamic therapy (aPDT) has been considered an effective and promising therapeutic alternative in this scenario. Briefly, this therapy is based on the activation of a non-toxic photosensitizing agent, known as photosensitizer (PS), by light at a specific wavelength generating cytotoxic singlet oxygen and free radicals. Virtually all studies related to aPDT involve a huge screening to identify ideal PS concentration and light dose combinations, a laborious and time-consuming process that is hardly disclosed in the literature. Herein, we describe an antimicrobial Photodynamic Therapy (aPDT) study against Enterococcus faecalis and Propionibacterium acnes employing methylene blue, chlorin-e6 or curcumin as PS. Similarities and discrepancies between the two bacterial species were pointed out in an attempt to speed up and facilitate futures studies against those clinical relevant strains. Susceptibility tests were performed by the broth microdilution method. Our results demonstrate that aPDT mediated by the three above-mentioned PS was effective in eliminating both gram-positive bacteria, although P. acnes showed remarkably higher susceptibility to aPDT when compared to E. faecalis. PS uptake assays revealed that P. acnes is 80 times more efficient than E. faecalis in internalizing all three PS molecules. Our results evidence that the cell wall structure is not a limiting feature when predicting bacterial susceptibility to aPDT treatment.

Photochemical and Electrochemical Triggered Bis(hydrazone) Switch.

Herein, we report the synthesis of a double hydrazone capable of undergoing photochemical E/Z isomerization through the imine double bonds. The bis(hydrazone) 1-E,E can be considered as a "two-arm" system in which the controlled movement of each arm is obtained by photo-modulation, making possible the appearance of two isolable metastable isomeric states 1-E,Z and 1-Z,Z. Such states are characterized by very specific structural, optical, and electrochemical properties. The latter allows the reversible return from either 1-E,Z or 1-Z,Z to the 1-E,E state. Our results are of great importance in the further development of molecular machines and photochemically controlled reactions by introducing for the first time double hydrazones as tunable photochemical switches.

Porphyrins as Catalysts in Scalable Organic Reactions.

Catalysis is a topic of continuous interest since it was discovered in chemistry centuries ago. Aiming at the advance of reactions for efficient processes, a number of approaches have been developed over the last 180 years, and more recently, porphyrins occupy an important role in this field. Porphyrins and metalloporphyrins are fascinating compounds which are involved in a number of synthetic transformations of great interest for industry and academy. The aim of this review is to cover the most recent progress in reactions catalysed by porphyrins in scalable procedures, thus presenting the state of the art in reactions of epoxidation, sulfoxidation, oxidation of alcohols to carbonyl compounds and C-H functionalization. In addition, the use of porphyrins as photocatalysts in continuous flow processes is covered.