Mastering nanostructured materials through H-bonding recognitions at interfaces

Abstract

The controlled engineering of functional architectures composed of π-systems with unusual opto-electronic properties is currently being investigated intensively from both fundamental research and technological application viewpoints. In particular, the exploitation of the supramolecular approach for the facile construction of multidimensional architectures, featuring cavities capable of hosting functional molecules, could be used in several applications, such as nanomedicine, molecular-based memory storage devices, and sensors. This paper highlights our recent strategies to use hydrogen-bonding interactions to prepare nanostructured functional architectures via the self-assembly of organic molecular modules studied at different interfaces. Fig. 1 (a) Chemical structures of bis-functionalized uracyl-bearing linear module (1) and melamine (2). Also, the equilibrium formation of the hybrid porous assembly via H-bonding interactions is shown; (b) STM image of the monocomponent self-assembly of 1; (c) STM image of the monocomponent self-assembly of 2; (d) STM image of the bicomponent self-assembly showing the hexagonal porous network formed; (e) The proposed assembly model is shown superimposed over a single hexagonal pore [44].922 model for the linear molecular wire assembly; (h) STM image of the tricomponent submonolayer architecture formed upon sequential sublimation of 1, 7, and 8 onto Ag(111) under UHV conditions (50 × 40 nm 2 ). The lower right inset shows an aggregate of 8 (7.7 × 7.7 nm 2 ); (i,j) proposed models and zoom in STM image of trimeric and pentameric assemblies, respectively [54].

Modular Engineering of H-Bonded Supramolecular Polymers for Reversible Functionalization of Carbon Nanotubes

“…Equimolar mixtures of the complementary molecules resemble those of their corresponding algebraic sum, except for the combinations of linear linkers 1a and 1b with 3 , which exhibit a weak new feature on the lower energy side (420 nm for [1a•3] n , 460 nm for [1b•3] n ; see the arrows in Figure ). The presence of this new feature at longer wavelengths is taken as a clue for the formation of supramolecular polymers arising from the combination of H-bond-directed self-assembly and self-organization processes ( vide infra ). ,,,,, On the contrary, the absorption spectra of solubilized MWCNTs did not reveal any features corresponding to the presence of either of the molecular components. The possible reasons for this observation are (i) overwhelming absorption of CNTs, (ii) supramolecular organization of molecules into new materials which perturbs their initial spectra, or (iii) a combination of these effects.…”

“…The rationale behind this approach is the possibility to exploit the ease of synthesis of the monomeric units, the combination of infinite number of units equipped with specific functionalities, and the predictability of the final targeted assemblies, to obtain well-defined yet flexible systems. Because of their directionality, strength, and versatility, multiple hydrogen bonds have held, by far, a most prominent place in engineering such polymeric arrays. ,− In addition, their dynamic and combinatorial nature may enable healing and adaptation, and thereby self-organization, by means of secondary weak interactions, such as π–π and van der Waals . Notwithstanding, the strength of the hydrogen bonds depends mainly on the solvent as well as number and sequence of the H-bond donors and acceptors.…”

Melting of Hydrogen Bonds in Uracil Derivatives Probed by Infrared Spectroscopy and ab Initio Molecular Dynamics

“…In this study, we investigate the stability and dissociation dynamics of hydrogen bonds by studying a pair of uracil-derivative molecular modules. Uracil-based molecular building blocks have already shown their potential as basic components in supramolecular chemistry, ,,− which means that their stability and breakdown mechanisms are of technological importance. In this context, infrared (IR) spectroscopy is very effective in the study of such hydrogen bonded complexes. , Special methods like matrix isolation (MI) spectroscopy combined with a more conventional IR spectroscopic method provide unique characterization opportunities as they permit the study of the molecular units both in their aggregated and free state.…”

Thermosolutal Self-Organization of Supramolecular Polymers into Nanocraters

“…In this field, the key concepts of molecular recognition through noncovalent interactions (i.e . , supramolecular chemistry) have been very effective tools for the preparation of nanostructured organic materials. − The exploitation of highly directional noncovalent interactions such as hydrogen bonds has been employed to induce the formation of supramolecular polymers, macromolecular structures in which single monomers are held together through reversible noncovalent interactions. − Our work on self-assembled and self-organized microstructures started with the preparation of vesicular nanostructures under temperature and solvent polarity control (i.e., through solvophobic/solvophilic interactions that are established in binary or ternary supramolecular adducts) by means of supramolecular ensembles formed through the recognition of complementary − monouracyl and bis-2,6-di(acetylamino)pyridyl H-bonding moieties . Along these lines, we also prepared a library of nine chromophoric acetylenic scaffolds also peripherally equipped with 2,6-di(acetylamino)pyridine or uracyl-type terminal fragments that, by taking advantage of self-assembly and self-organization, drove the formation of nanostructures of different shapes and sizes such as nanoparticles, nanovesicles, nanofibers, and nanorods, also with helicoidal or circular variants .…”