Control over Dethreading Kinetics Allows Evaluating the Entropy Stored in an Interlocked Molecular Machine Out-of-Equilibrium.

The operation of nanomachines is fundamentally different from that of their macroscopic counterparts. In particular, the role of solvent is critical yet rarely associated with machine functionality. Here, we study a minimal model of one of the most advanced molecular machines to gain control of its operation by engineering components and the employed solvent. Operation kinetics were changed over more than four orders of magnitude and could be modulated by solvent. Leveraging solvent properties, it was possible to monitor the relaxation of the molecular machine towards equilibrium and measure the heat exchanged in the process. Our work expands the capabilities of acid-base powered molecular machines, confirming experimentally that such systems have a dominant entropy content.

Transfer of Axial Chirality to the Nanoscale Endows Carbon Nanodots with Circularly Polarized Luminescence.

We report the synthesis, purification and characterization of chiral carbon nanodots starting from atropoisomeric precursors. The obtained atropoisomeric carbon nanodots are soluble in organic solvents and have good thermal stability, which are desirable features for technological applications. The synthetic protocol is robust, as it supports a number of variations in terms of molecular doping agents. Remarkably, the combination of axially chiral precursors and 1,4-benzoquinone as doping agent results in green-emissive carbon dots displaying circularly polarized luminescence. Dissymmetry factors of |3.5|×10-4 are obtained in solution, without the need of any additional element of chirality. Introducing axial chirality expands the strategies available to tailor the properties of carbon nanodots, paving the way for carbon nanoparticles that combine good processability in organic solvents with engineered advanced chiroptical properties.

Solvent-Free Pd-Catalyzed Heteroaryl-Aryl Coupling via C-H Bond Activation for the Synthesis of Extended Heteroaromatic Conjugated Molecules.

Direct arylation of thienopyrrolodione, diketopyrrolopyrroles, benzodithiophene derivatives, and fluorinated heteroarenes with functionalized aryl iodides is proven in solvent-free and non-anhydrous conditions. The reaction is performed in the presence of air and tolerates several functional groups on both the coupling partners, enabling a convenient synthesis of extended heteroaromatic conjugated molecules.

Synthesis and applications of amino-functionalized carbon nanomaterials.

Carbon-based nanomaterials (CNMs) have attracted considerable attention in the scientific community both from a scientific and an industrial point of view. Fullerenes, carbon nanotubes (CNTs), graphene and carbon dots (CDs) are the most popular forms and continue to be widely studied. However, the general poor solubility of many of these materials in most common solvents and their strong tendency to aggregate remains a major obstacle in practical applications. To solve these problems, organic chemistry offers formidable help, through the exploitation of tailored approaches, especially when aiming at the integration of nanostructures in biological systems. According to our experience with carbon-based nanostructures, the introduction of amino groups is one of the best trade-offs for the preparation of functionalized nanomaterials. Indeed, amino groups are well-known for enhancing the dispersion, solubilization, and processability of materials, in particular of CNMs. Amino groups are characterized by basicity, nucleophilicity, and formation of hydrogen or halogen bonding. All these features unlock new strategies for the interaction between nanomaterials and other molecules. This integration can occur either through covalent bonds (e.g., via amide coupling) or in a supramolecular fashion. In the present Feature Article, the attention will be focused through selected examples of our approach to the synthetic pathways necessary for the introduction of amino groups in CNMs and the subsequent preparation of highly engineered ad hoc nanostructures for practical applications.