From self-assembly to noncovalent synthesis of programmable porphyrins' arrays in aqueous solution.

Self-organization is the driving force that led to the evolution of life. Rationalization of the spontaneous self-assembly paradigm will offer tremendous potentialities to obtain a wide variety of complex systems, having specific functionality and properties. Herein, we will propose an overview of the developments in non-covalent syntheses of multi-porphyrin supramolecular species in aqueous solution. This work took inspiration from the pioneering studies aimed at rationalizing the spontaneous aggregation processes, governed by conventional solution properties (i.e. pH, ionic strength, and concentration). The more recent chemical strategies, to hierarchically manipulate the cooperative nature of weak interactions to design and synthesize supramolecular entities having pre-determined structure and properties, demonstrate the feasibility to attain, in a reproducible manner, molecular organization to supramolecular levels. In particular, calixarene-porphyrin species represents concrete evidence of a quantitative complexation, governed by precise hierarchical rules, which together with a rational functionalization of the molecular components leads to supramolecular entities of well-defined and tunable stoichiometry. These systems, thus, represent fertile ground to envisage and implement controlled self-organization strategies as bottom up methodologies to obtain supramolecular nanostructures and smart nanomachines.