Topic 1: Supramolecular organic nanochemistry at interfaces.

Since its creation at the end of 2006, our team has been very active in the field of supramolecular organic chemistry at interfaces, with the objective of taking advantage of the supramolecular approach as a route to build defined two- and three-dimensional nano-patterned organic networks. We have validated the concept for which complementary H-bonding interactions can serve as powerful and versatile tool for tuning the shape of materials giving access to an enormous number of structurally-organized architectures, mastering their organization from the nanoscale up to the macroscopic level [Chem. Eur. J.200915, 7004; Coord. Chem. Rev., 2010, 254, 2342; Pure Appl. Chem., 2010, 10, 917; Nanoscale, 2013, 5, 8837]. In a collaborative research program with the group of Prof. M. Stohr (University of Groningen, Holland), exploiting the triply H-bonded uracil-2,6-diamidopyridine recognition motif linked to oligo(phenylene-ethynylene) molecular wires, we have reported the first example, at that time, of a simultaneous three-components H-bonded assembly on Ag(111) surfaces by STM analysis under ultrahigh vacuum conditions (UHV). [Angew. Chem. Int. Ed.200847, 7726]

 Simultaneously, for the first time, we also reported the first writable organic-based surfaces based on thermally switchable 2D porous assembly [Chem. Commun.2009, 3525]. Discrete assemblies, featuring hosting properties towards hydrophobic porphyrin guests, have been also formed using complementary angular modules. The multicomponent non-covalent H-bonded hollowed assemblies featuring polygonal porous domains (in coll. with Prof. P Samori at Universisty of Strasbourg, France) have also been comprehensively investigated at the solid-liquid interfaces, for the first time showing that both the network and the phase depend on the molecular geometry, concentrations and the peculiar chemical structure [Chem. Commun.2008, 5289; Adv. Funct. Mater.200919, 1207; J. Am. Chem. Soc.2009131, 509; J. Am. Chem. Soc.2009131, 13062]. Passing from the molecular to the nanoscale, our team has also shown how the use of H-bonding allowed the tuning of the size and shape of uniform architectures enabling a morphological change to occur from nanoparticle and vesicles [Chem. Commun.2009, 2830]. The formation of helicoidally organized rods, crater-, prism- and crown-like morphologies have been also fully  described [Chem. Eur. J.201017, 3262; Langmuir201127, 1513].

Aiming at introducing asymmetric properties and relate molecular and macroscopic chirality [ChemPlusChem201479, 895], we have very recently engineered a new family of BINOLs derivatives undergoing solvent-dependent nanostructuration. Depending on the solvophobic properties of the liquid media, the material can be moulded into spherical, rod-like, fibrous and helical morphologies [J. Am. Chem. Soc.2015137, 8150]. This behaviour is interpreted as a consequence of an interplay between the degree of association of the H-bond recognition, the vapour pressure of the solvent and the solvophobic/solvophilic character of the supramolecular adducts in the different solutions under dynamic conditions, namely during solvent evaporation conditions at room temperature.

In collaboration with the group of Prof. J. Barth and Prof. W. Auwarter (TUM), we have described for the first time the formation of discrete, tunable and hollowed cyclic supramolecular architectures on insulating boron-nitrate [J. Am. Chem. Soc.2015137, 2420] and on metal surfaces exploiting metal-coordination bonding interactions with pyridyl-bearing ligands [Nano Lett.201010, 122; J. Am. Chem. Soc.2010132, 6783; ACS Nano20106, 4936], the structure of which could be tailored by the geometry, conformational flexibility and functionality of the porphyrin molecular modules. Recently, we have also reported the first patterning of lanthanide and transition metal atoms on surfaces exploiting the orthogonal coordination properties of tetrapyridyl porphyrins [Angew. Chem. Int. Ed.201554, 6163]. Expanding the topic, a series of differently substituted pyridyl-bearing pyrenyl modules [ACS Nano201610, 7665] have been prepared, all showing a different self-assembly behavior (e.g., spangling, crocheting and knitting) depending on the spatial disposition of the pyridyl groups. Extended porous networks showing inherent flexibility and adaptability properties have been prepared exploiting competing non-covalent interactions, using tripodal modules like 1,3,4-tris-pyridyl-benzene [ACS Nano20126, 4258; Chem. Eur. J.2013, 14143]. In a parallel study, in collaboration with the groups of Prof. G. Costantini (Warwick University, United Kingdom) and Prof. A. De Vita (King’s College, United Kingdom), we demonstrated that polyaromatic hydrocarbons form nanostructures at the interface that are ruled by an interplay between van der Waals attractions and intermolecular repulsions, the latter driven by reversible molecule-substrate charge transfer [ACS Nano20148, 12356, Nanoscale, 20168, 19004].

Aiming at introducing a certain functionality on porous self-assembled organic networks, we have very recently initiated a novel research project (sponsored by the ERC Starting Grant 2012, COLORLANDS) in which, taking advantage of the molecular self-assembly, we seek to create a new generation of periodically-organized organic architectures that can structurally control the arrangement of molecular chromophores and/or fluorophores. The ultimate aim is to create a library of supramolecularly-assembled architectures emitting or adsorbing light throughout the visible region that, depending on their spatial organization, are suitable for producing versatile organic materials for device implementation (e.g. an OLED with luminophores or an artificial “leafs” mimicking natural antenna if hosting chromophores). In this respect, we conceived a facile and versatile protocol for the simultaneous use of three orthogonal dynamic covalent reactions, namely disulfide, boronate and acyl hydrazine formation. Using a pre-programmed a-helix peptide, we conceived a facile and versatile protocol to spatially organize tailored blue, red and yellow chromophores [Angew. Chem. Int. Ed.201554, 15739].

Comments are closed.