The leitmotiv of the scientific
activity of Alberto Credi is the design and photophysical,
photochemical and electrochemical investigation of molecular and
supramolecular systems capable of performing useful functions and
that, as such, can be viewed as examples of devices and machines at
the molecular level.
The scientific profile and the complete list of publications can be downloaded here.
The research activity can be categorized into three main themes:
1. Artificial molecular
machines and motors
This research line deals with the
design, synthesis and study of multicomponent species (in most
cases rotaxanes, catenanes and related species) capable of
performing mechanical motions of their molecular components in
response to external stimulation (addition of chemical reactants,
application of electric potentials, light irradiation). The investigations are focussed on the use of light as an energy source, and on the possibility of developing systems that can operate autonomously far from equilibrium by dissipating the external energy input. The aim is
the construction of mechanical nanodevices that can carry out
useful functions such as control of membrane permeability, uptake
and release of other molecules, up to mechanical actuation on the
micro- and macroscopic scales (molecular muscles).
2. Molecular and
supramolecular systems for information processing
The objective of this research
line is the development of chemical sistems capable of gathering,
processing and storing information. Such activities are part of the
“bottom up” approach to miniaturization, which is expected to
enable the costruction of nanoscale devices not achievable by the
current “top down” technologies. The bottom up approach should not
only lead to smaller and more powerful computers, but also to new
technologies capable of revolutionizing medicine, producing a
wealth of new materials, providing new energetic resources and
solving environmental problems. Among the examined systems are
molecular switches, wires, plug/socket devices, extension cables,
memories and logic circuits.
3. Synthesis and study of
the photophysical, photochemical and electrochemical properties of
complex molecular species, nanoparticles and materials
The objective of this research
line is to increase the basic knowledge on the physicochemical
properties of molecules, supermolecules, and nanoparticles. The
investigated topics are: thermodynamic and kinetic aspects of
self-assembly reactions of host-guest systems, photoisomerization
processes in azobenzene-type species, photophysical and redox
behaviour of organic molecules and metal complexes, photocatalytic
properties of titania nanostructured surfaces, photophysical and
redox behaviour of inorganic nanoparticles and their interaction
with molecular species, light-induced control of the physicochemical properties of photoreactive materials.
The research themes are devoted to
the design and construction of supramolecular species capable of
performing predetermined useful functions. These studies are of
fundamental importance in the rapidly growing fields of nanoscience
and nanotechnology, in reference to the “bottom-up” approach for
the realization of functional structures of nanometer
size.
The objectives of the presented
research topics are:
1. Devise and characterize
supramolecular species in which some molecular components can be
moved with respect to others in response to suitable external
stimulation. Devices of this kind are currently the subject of
great interest and are referred to as molecular machines. The
stimuli employed to make such machines work are of chemical,
electrochemical, and photochemical nature. Promising supermolecules
in this regard are pseudorotaxanes, rotaxanes, catenanes and
related species, host-guest systems, dendrimers.
2. Devise and investigate
molecular and supramolecular systems capable of delivering output
signals in response to specific input signals, in order to mimick
the binary logic functions performed in electronic circuits. Among
the targeted systems are host-guest complexes, rotaxanes,
dendrimers, metal complexes, electrochromic and photochromic
species, multistate-multifunctional systems.
3. Design and realize
supramolecular species that can collect, transmit, store and
process light signals. Devices of this type are, e.g., molecular
antennas, wires, plug-socket and extension systems,
charge-separation devices, multistate-multifunctional species. Such
studies are of crucial importance in view of the construction of
devices for the conversion of solar energy into chemical energy, as
well as ultraminiaturized devices for information processing
(chemical computers). To this purpose, dendrimers, host-guest
systems, rotaxanes, polynuclear metal complexes, photochromic
systems can be identified as suitable chemical species.
A common objective of these
research topics is to move from solution studies to the
characterization of systems deposited on surfaces and at
interfaces, in the attempt of realizing an “interfacement” between
the molecular and the macroscopic world. Such aspect can be
explored with the attachment of the investigated supramolecular
species to nanostructured (e.g. nanoparticles) or macroscopic (e.g.
electrodes) surfaces by exploiting, for example, the self-assembled
monolayer and Langmuir-Blodgett techniques.
In order to obtain supramolecular
species that can perform predetermined functions, that is, having
desired chemical, photochemical and electrochemical properties, the
strict cooperation between researchers in different branches of
chemistry (synthetic chemists, physical chemists) and in other
fields (materials science, physics, biochemistry, engineering,
computer science) is of fundamental importance. The methods that
will be most commonly employed for the characterization of the
compounds, their components and model species are steady state
absorption and luminescence spectroscopic techniques. Time resolved
spectroscopic techniques (laser flash photolysis, phase-modulation
shift, time-correlated single-photon counting, stopped-flow
methods) will also be used with the purpose of investigating the
dynamics of the processes induced by photonic, electrochemical or
chemical stimulation. These measurements will be complemented by
voltammetric and spectroelectrochemical experiments with both
conventional and ultramicro-electrodes. Computer simulations of the
experimental data (voltammetric curves, kinetic traces, titration
data, etc.) will be performed in order to determine the mechanism
and the relevant parameters of the examined processes.
