1,721,025 research outputs found
Design, Synthesis and Characterization of new Supramolecular Architectures
No full textThis thesis focuses on the bottom-up design, construction and operation of supramolecular systems capable of behaving as devices and machines on the molecular scale, which is a topic of great interest in nanoscience and a fascinating challenge in nanotechnology. In particular, the systems investigated here include: polyviologen dendrimers capable of behaving as hosts and chargestoring devices; molecular machines based on pseudorotaxanes/rotaxanes and operated by photoinduced proton transfer, or photoisomerization reactions; and a simple unimolecular multiplexer/demultiplexer. The systems have been characterized using a variety of techniques including absorption and emission spectra, laser flash photolysis, NMR spectroscopy, electrochemical experiments, stopped flow measurements. This research addresses a large number of open problems in the nanosciences, dealing with a wide range of the most advanced applications of supramolecular systems
Azobenzene: A Photoactive Building Block for Supramolecular Architectures
No full textThe development of nanoscale systems capable to perform specific functions under external control is a challenging task and a fascinating objective in Chemistry. Photochromic compounds undergo radical changes in their physico-chemical properties upon light excitation, for this reason they are valuable building blocks for the construction of photo-controllable molecular devices, machines and materials. The E-Z photoisomerization of azobenzene has been known for almost 80years and - owing to its high efficiency and excellent reversibility - has been widely employed to introduce an element of photo-control in a large variety of compounds, biomolecules, nanosystems and materials. Here we present some of our research results highlighting how this outstanding photochrome can be utilized to develop systems with light-induced functionalities
Photo- and Redox-Driven Artificial Molecular Motors
Full text linkDirected motion at the nanoscale is a central attribute of life, and chemically driven motor proteins are nature's choice to accomplish it. Motivated and inspired by such bionanodevices, in the past few decades chemists have developed artificial prototypes of molecular motors, namely, multicomponent synthetic species that exhibit directionally controlled, stimuli-induced movements of their parts. In this context, photonic and redox stimuli represent highly appealing modes of activation, particularly from a technological viewpoint. Here we describe the evolution of the field of photo- and redox-driven artificial molecular motors, and we provide a comprehensive review of the work published in the past 5 years. After an analysis of the general principles that govern controlled and directed movement at the molecular scale, we describe the fundamental photochemical and redox processes that can enable its realization. The main classes of light- and redox-driven molecular motors are illustrated, with a particular focus on recent designs, and a thorough description of the functions performed by these kinds of devices according to literature reports is presented. Limitations, challenges, and future perspectives of the field are critically discussed
Manipulating Chemicals at Small‐ and Semimicro‐Scale in Inert Atmosphere
Full text linkThe rational use of chemicals requires that their properties be compatible with the planned application. These properties are modified by the interactions to which the chemical substance is subjected, among which particularly relevant are those with the components of the lab atmosphere, collectively labelled air sensitivity. The air sensitivity of chemicals is remarkably amplified in the presently common small- and semimicro-scale samples and operations, due to the increased surface-to-mass ratio with respect to the time-honoured multigram scale. In this note we present ergonomy-aware procedures implemented in small- and semimicro-scale laboratory operations, which enable to work easily in an inert atmosphere without the need for awkward or expensive apparatuses such as glove box or vacuum line
Gearing up molecular rotary motors: A light- and heat-driven molecular machine achieves locked, synchronous motion
No full textA light- and heat-driven molecular machine achieves locked, synchronous motio
Rigidification or interaction-induced phosphorescence of organic molecules
Full text linkPhosphorescent materials are mostly based on metal complexes. Metal-free organic molecules usually display phosphorescence only in a rigid matrix at 77 K. In the last few years, there has been increasing interest in the design of organic molecules displaying long-lived and highly intense room-temperature phosphorescence, an extremely difficult task since these two properties are generally conflicting. This review reports the most recent and tutorial examples of molecules that are weakly or non-phosphorescent in deaerated fluid solution and whose room temperature phosphorescence is switched on upon aggregation. The examples are divided into two classes according to the mechanism responsible for switching on phosphorescence: (i) rigidification by crystallization or by encapsulation in a polymeric matrix and (ii) interaction with other molecules of the same type (self-aggregation) or a different type by taking advantage of heavy-atom effects
Setup for Semimicro Pressure Filtration
No full textSemimicro pressure filtration is carried out by pressurizing a suspension through pushing the piston of a gas-filled plastic syringe whose needle perforates the closure of a cylindrical filter funnel. Basic features as well as pros and cons of vacuum and pressure filtration are pointed out and compared to support rational choice between the two procedures
Light‐Driven Molecular Machines
No full textIn the last 40 years, the opinion of most researchers has moved from considering artificial molecular machines as simple laboratory curiosities to viewing them as valuable tools to impart novel functionalities and properties to advanced materials and multicomponent systems. In this chapter, we present an overview of the progress on the design and realization of light-activated molecular machines and on their different applications. This research field has always been in close relationship with the study of photoswitchable and photochromic compounds. Indeed, it can be confidently said that at the heart of any light-activated nanomachine, a photoswitchable moiety is at work.
After a brief description of the basic type of photoinduced processes that light-activated nanomachines exploit for their operation, a concise description of the main classes of nanomachines is presented. The chapter follows with examples in which the nanoscale motion of the machine is translated in an advanced functionality. These include switchable catalysts, linear and rotary transporters of small molecular cargos, and supramolecular pumps. Furthermore, examples in which the collective operation of an assembly of molecular machines is harnessed to perform tasks at the microscale and macroscale in hard and soft materials are also reviewed. In particular, functionalized surfaces, metal–organic frameworks, polymers, and self-assembled nanostructures are described wherein the nanoscale movement of embedded molecular machines is amplified, allowing the realization of muscle-like actuators, microfluidic devices, and polymeric materials for light energy transduction and storage
Pompe molecolari azionate dalla luce
Full text linkLA REALIZZAZIONE DI MOTORI MOLECOLARI ARTIFICIALI IN GRADO DI CONVERTIRE ENERGIA IN LAVORO MECCANICO
È UNA SFIDA AFFASCINANTE DELLA NANOTECNOLOGIA E NECESSITA DI SISTEMI CHIMICI IN GRADO DI FUNZIONARE LONTANO
DALL’EQUILIBRIO. QUESTO ARTICOLO DESCRIVE LA PROGETTAZIONE E LA COSTRUZIONE DI UN SEMPLICE SISTEMA
SUPRAMOLECOLARE NEL QUALE L’IRRADIAZIONE LUMINOSA PROMUOVE IL TRANSITO DIREZIONALE DI UN MACROCICLO
LUNGO UN ASSE MOLECOLARE NON SIMMETRICO, PONENDO LE BASI PER LO SVILUPPO DI POMPE MOLECOLARI ARTIFICIAL
The eternal youth of azobenzene: New photoactive molecular and supramolecular devices
No full textThe development of multicomponent chemical systems that can perform predetermined functions
under external control – i.e., molecular devices – is a challenging task in chemistry and a fascinating objective
in the frame of a bottom-up approach to nanostructures. Photochromic units undergo profound changes
in their chemical and/or electronic structure upon light excitation, and are highly interesting for the construction
of photocontrollable molecular devices, machines and materials. The E–Z photoisomerization of
azobenzene – owing to its high efficiency, excellent reversibility and significant physico-chemical differences
between the two forms – is a highly useful reaction in this regard. Azobenzene photoisomerization has been
known for almost 80 years and has been exploited to implement light-induced functionalities with a large
variety of compounds, biomolecules, nanosystems and materials. Here we present some of our recent investigations
highlighting how this outstanding photochrome can be utilized to develop (supra)molecular systems
with valuable light-induced functionalities
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