DI SALVO Florencia
congresos y reuniones científicas
LOW-MOLECULAR-WEIGHT AMINO-ACID-BASED DERIVATIVES: FROM ORGANOGELS TO SINGLE CRYSTALS AND MESOCRYSTALS
FLORENCIA DI SALVO; FEDERICO MOVILLA; JUAN MANUEL REY; OLGA C. SÁNCHEZ M.
Congreso; XIII Reunión anual AACr; 2017
Amino acids are able to self-assemble into ordered superstructures, also called mesocrystals when they are subjected to certain crystallization conditions such as, pH, supersaturation level and the use of additives . While different morphologies of crystalline arrangements are known, the greatest interest lies in the obtaining of three-dimensional (3D) self-assemblies with hierarchical architectures that can contribute to the knowledge of the controlled manufacture of nanoscale materials and novel devices. Besides, self-assembly strategies applied to low-molecular weight building blocks can conduct to supramolecular gels . The obtaining of both, supramolecular gels or crystalline materials (mesocrystals or single crystals) is governed by the presence non-covalent interactions resulting in spanning network that can immobilize solvents for the first ones or, self-assemble mainly between the low molecular weight building blocks, to give place to the second ones. Thus, there is a delicate balance for a low-weight molecule to behave as a gelator or crystal. In this work we present a new family of chiral L-amino-acid-based low-weight molecules which behave as excellent building blocks to the construction of supramolecular gels or crystalline structures depending on the fine tune of the functional groups and the environment conditions (temperature, solvent and/or pH). Compounds 1-3 are obtained in their zwitterionic form after a Schiff base reaction followed by reduction, between the aldehyde piperonal and L-Alanine (Ala), L-Phenylalanine (Phe) and L-Tyrosine (Tyr), respectively. Crystallization experiments using organic solvents with compounds 1 and 3 conduct mainly to polycrystalline materials and 2 gives place to crystalline superstructures with spherical morphologies attributed to the different solubility and supramolecular properties conferred by the amino acid bone. All derivatives are soluble in basic solutions after the deprotonation of the zwitterion and for these mixtures, spherical-like mesocrystals are obtained after slow evaporation of the solvent. On the other hand, after slow diffusion of hydrogen chloride acid vapors in basic solutions of 2, single crystals suitable for X-ray diffraction studies are obtained. Only the derivative of Phe gives place to supramolecular gels showing again a direct correlation between the identity of the building block and the supramolecular behavior when compares compound 1-3. In conclusion, it is possible to suggest that the presence and directionality of certain functional groups and the intermolecular interactions developed, such as the existence or not of the OH and the phenyl group, are key factors in the mechanism of self-assembly into hierarchical structures, single crystals or even supramolecular organogels. ` H. Jiang, et al. Cryst. Growth Des, 11, (2011) 3243?3249, and references therein. L. E. Buerkle & S. J. Rowan Chem. Soc. Rev. 41 (2012) 6089?6102.