Shape-memory effects and mechanical actuations can be indeed generated from objects of various chemical nature [3][4][5] (e.g., metallic alloys, ceramics, liquid crystals, or polymers), and they are often supported by a combination of bottom-up and top-down structural engineering techniques going from surfaces to 3D materials (e.g., supramolecular self-assembly, photopatterning, microfluidics, or inkjet printing). [6,7] Various stimuli can generate their response (e.g., molecules, temperature, light, electrical potential, or mechanical stress) and their functioning principles vary largely from one system to another, involving a number of physical phenomena which can take place at the (macro)molecular level and which are transferred toward higher length scales (e.g., polarity, solubility-such as lower critical solution temperature (LCST), osmotic pressure, surface energy, or phase transition). It should also be mentioned that bio-inspiration is often a driving force in the design of such artificial materials as many smart mechano-active systems with adaptable properties are found in nature (e.g., stiffness change of sea cucumber, adaptive toughness of spider silk, closure of mimosa leaves when touched, or opening of seed pods). [8][9][10] Since the early 2000s, exciting opportunities have emerged in the scientific community for making use of artificial molecular machines as the elementary responsive building blocks in new types of stimuli-responsive materials. This approach is fundamentally disruptive compared to the others developed so far, because it aims to exploit precisely controlled mechanical motions at molecular level (produced by the machines), and to amplify them in collective mechanical motions taking place at larger dimensions up to the material's length scale. The most prominent example of what could be potentially achieved in the far future by such artificial materials is also found in nature, in the form of striated muscle tissue. In muscles, by using adenosine triphosphate (ATP) as chemical fuel, millions of myosin motors, which individually cycle hundreds of few nanometers scale actuations, are able to pull synchronously on sliding actin filaments and to produce micrometric contractions of sarcomeric units. Further hierarchical organizations of sarcomeres in bundled fibrils and fibers result in a macroscopic contraction of the muscle. At that point, and before describing selected examples of (much simpler) artificial systems, it is important for the readers who would not be familiar with molecular machines to first introduce more precisely terms and notions which define their nature and actuation principles. 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. Maki...

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.

A successful end-to-end continuous flow synthesis of pure curcumin (1) and two other natural derivatives present in turmeric is described.

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.

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.

In article number 1906036, Nicolas Giuseppone and co‐workers report on the construction of stimuli‐responsive materials based on artificial molecular machines. They show that integration, orientation, and interfacing of large assemblies of molecular machines can produce collective actuations up to the generation of macroscopic motions.

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