Supramolecular architectures of porphyrins on surfaces: The structural evolution from 1D to 2D to 3D to devices

Tetrapyrrolic macrocycles, such as porphyrins, belong to a class of distinctively multifunctional biomolecules playing a central role in fundamental natural processes such as electron transfer, oxygen transfer, and light-harvesting, and their use to mimic these biological events in nanotechnological devices would be of obvious benefit. Despite the synthetic and physical achievements, a technical impediment towards the exploitation of such porphyrin-based architectures in applicative devices is that they cannot be singularly addressed in solution or at solid state, as they must be interfaced with the external world. They also need to show durability and functionality under the extreme conditions that are normally used in operating practical devices. Typically, porphyrin architectures have been investigated in solution, however, the tendency in current research is to deposit functional porphyrin derivatives on the surfaces of bulk materials such as metals or semiconductors and investigate the resultant hybrid surfaces using STM. In this review, we have illustrated the trends in supramolecular nanopatterning of porphyrin derivatives at different interfaces. Various strategies for the construction of nanoscale architectures at different interfaces are described along the course of the review, including sublimation under UHV conditions, adlayer formation by immersion of a surface in a liquid or deposition of a solution. The discussion of assemblies on surfaces commences with a description of the very recent developments in the remarkably precisely controlled construction of discrete assemblies on surfaces under UHV conditions. Subsequently, extended 2D arrays formed in both ambient conditions at the liquid-solid interface, as well as under UHV conditions have been discussed along with the ability of certain 2D self-assemblies to accommodate guest molecules. The last section of the review deals with porphyrin assemblies featuring three-dimensional properties, with a particular focus on those systems in which the third-dimension introduces functionality such as gas-storage, catalysis and a molecular motor. © 2010 Elsevier B.V.