Research
Our group works in the field of Supramolecular Chemistry and is currently focused on three main topics:
Our group works in the field of Supramolecular Chemistry and is currently focused on three main topics:
The wide interest towards molecular machines is witnessed by the Nobel Prize recently assigned to Profs. Feringa, Sauvage and Stoddart (2016). An important role in the frame of molecular machines has been played by catenanes and rotaxanes in which the relative position of the components is controlled by the presence of switchable functions. The distinctive feature of these systems is the ability to perform back and forth motions, i.e. a series of two or more roto-translations during which the machine varies from an initial state A to one or more intermediate states B’, B”,…, and eventually reverts back to the initial state A. The transition between states A and B usually requires the sequential addition of a fuel and a counter stimulus, such as an acid and a base, a reductant and an oxidant, irradiation with light of different wavelengths and the like. Conversely, systems in which only one stimulus is required to guarantee the operation of a back and forth motion are rare. We realized one of these systems, which is based on the decarboxylation reaction of a series of activated carboxylic acids. In a first step the acid donates a proton to an acid-base operated molecular switch that passes from state A to state B. The subsequent decarboxylation of the resulting carboxylate produces a carbanion that is a very strong base able to take back the proton from the protonated switch to restore the state A from state B. Our effort is now devoted to the development of a series of chemical fuels with improved features, which can be used in the operation of any acid-base operated molecular machine or more in general acid-base operated dissipative systems (a dissipative system can be defined as a system which persists in a functional state as long as a fuel is present).
The wide interest towards molecular machines is witnessed by the Nobel Prize recently assigned to Profs. Feringa, Sauvage and Stoddart (2016). An important role in the frame of molecular machines has been played by catenanes and rotaxanes in which the relative position of the components is controlled by the presence of switchable functions. The distinctive feature of these systems is the ability to perform back and forth motions, i.e. a series of two or more roto-translations during which the machine varies from an initial state A to one or more intermediate states B’, B”,…, and eventually reverts back to the initial state A. The transition between states A and B usually requires the sequential addition of a fuel and a counter stimulus, such as an acid and a base, a reductant and an oxidant, irradiation with light of different wavelengths and the like. Conversely, systems in which only one stimulus is required to guarantee the operation of a back and forth motion are rare. We realized one of these systems, which is based on the decarboxylation reaction of a series of activated carboxylic acids. In a first step the acid donates a proton to an acid-base operated molecular switch that passes from state A to state B. The subsequent decarboxylation of the resulting carboxylate produces a carbanion that is a very strong base able to take back the proton from the protonated switch to restore the state A from state B. Our effort is now devoted to the development of a series of chemical fuels with improved features, which can be used in the operation of any acid-base operated molecular machine or more in general acid-base operated dissipative systems (a dissipative system can be defined as a system which persists in a functional state as long as a fuel is present).
Dynamic Combinatorial Chemistry and Macrocyclization Equilibria (go to selected publications on the topic)
Dynamic Combinatorial Chemistry and Macrocyclization Equilibria (go to selected publications on the topic)
The number of irreversible reactions used in the formation of synthetically useful covalent bonds largely outweighs that of reversible ones. Yet, the last period has witnessed a renewal of interest in the use of reversible reactions for synthetic purpose thanks to the birth of Dynamic Combinatorial Chemistry (DCC) mainly due to J.-M. Lehn, J. K. M. Sanders and S. Otto. In particular DCC has the potential to be a powerful tool for the synthesis of macrocyclic species under thermodynamic control because efficient cyclic receptors may be selected among a family of interconverting linear and cyclic members of a dynamic library (DL) upon the addition of a suitable template (T), via repeatedly occurring bond dissociation-recombination processes. Some reversible reactions such as acetal exchange, transimination and imine and olefin metathesis have been studied in our lab, in the frame of DCC. Furthermore, we are strongly interested in the physico-chemical laws governing the macrocyclization reactions that are very often at the basis of the systems studied in DCC. In the last period we have been working on a re-elaboration of the Jacobson-Stockmayer theory, which includes mechanical bonded species such as catenanes, into the classical treatment, and on experimental results proving our theories.
The number of irreversible reactions used in the formation of synthetically useful covalent bonds largely outweighs that of reversible ones. Yet, the last period has witnessed a renewal of interest in the use of reversible reactions for synthetic purpose thanks to the birth of Dynamic Combinatorial Chemistry (DCC) mainly due to J.-M. Lehn, J. K. M. Sanders and S. Otto. In particular DCC has the potential to be a powerful tool for the synthesis of macrocyclic species under thermodynamic control because efficient cyclic receptors may be selected among a family of interconverting linear and cyclic members of a dynamic library (DL) upon the addition of a suitable template (T), via repeatedly occurring bond dissociation-recombination processes. Some reversible reactions such as acetal exchange, transimination and imine and olefin metathesis have been studied in our lab, in the frame of DCC. Furthermore, we are strongly interested in the physico-chemical laws governing the macrocyclization reactions that are very often at the basis of the systems studied in DCC. In the last period we have been working on a re-elaboration of the Jacobson-Stockmayer theory, which includes mechanical bonded species such as catenanes, into the classical treatment, and on experimental results proving our theories.
Non-heme iron and manganese complexes are emerging as powerful and versatile catalysts in several oxidative transformations. Remarkable advantages associated with such catalysts are the ease of their synthesis and the related use of environmentally friendly compounds such as H2O2 as terminal oxidants. The most investigated non-heme iron- and manganese catalytic complexes are based on aminopyridine ligands, although a number of imine-based ligands have been recently considered. We have lately used a supramolecular approach in the field of aminopyridine-based iron and manganese complexes to catalyze the selective oxidation of particular methylenic positions of long, linear, primary amines. The binding event responsible of the recognition between the catalyst and the substrate allows for an unprecedented selectivity. Concerning the imine-based catalysts, we introduced an imine-based iron complex, easily prepared in situ from cheap and commercially available starting materials, which was demonstrated to be able to catalyze the oxidation of aliphatic and aromatic C−H bonds. We are currently investigating on the possible expansion of the synthetic scope of our supramolecular aminopyridine-based complex and on the mechanism of action of the imine-based iron complex.
Non-heme iron and manganese complexes are emerging as powerful and versatile catalysts in several oxidative transformations. Remarkable advantages associated with such catalysts are the ease of their synthesis and the related use of environmentally friendly compounds such as H2O2 as terminal oxidants. The most investigated non-heme iron- and manganese catalytic complexes are based on aminopyridine ligands, although a number of imine-based ligands have been recently considered. We have lately used a supramolecular approach in the field of aminopyridine-based iron and manganese complexes to catalyze the selective oxidation of particular methylenic positions of long, linear, primary amines. The binding event responsible of the recognition between the catalyst and the substrate allows for an unprecedented selectivity. Concerning the imine-based catalysts, we introduced an imine-based iron complex, easily prepared in situ from cheap and commercially available starting materials, which was demonstrated to be able to catalyze the oxidation of aliphatic and aromatic C−H bonds. We are currently investigating on the possible expansion of the synthetic scope of our supramolecular aminopyridine-based complex and on the mechanism of action of the imine-based iron complex.