Chiral Cyclobutane β-Amino Acid-Based Amphiphiles: Influence of Cis/Trans Stereochemistry on Condensed Phase and Monolayer Structure.
New diastereomeric nonionic amphiphiles, cis- and trans-1, based on an optically pure cyclobutane β-amino ester moiety have been investigated to gain insight into the influence exerted by cis/trans stereochemistry and stereochemical constraints on the physicochemical behavior, molecular organization, and morphology of their Langmuir monolayers and dry solid states. All these features are relevant to the rational design of functional materials. trans-1 showed a higher thermal stability than cis-1. For the latter, a higher fluidity of its monolayers was observed when compared with the films formed by trans-1 whose BAM images revealed the formation of condensed phase domains with a dendritic shape, which are chiral, and all of them feature the same chiral sign. Although the formation of LC phase domains was not observed by BAM for cis-1, compact dendritic crystals floating on a fluid subphase were observed beyond the collapse, which are attributable to multilayered 3D structures. These differences can be explained by the formation of hydrogen bonds between the amide groups of consecutive molecules allowing the formation of extended chains for trans-1 giving ordered arrangements. However, for cis-1, this alignment coexists with another one that allows the simultaneous formation of two hydrogen bonds between the amide and the ester groups of adjacent molecules. In addition, the propensity to form intramolecular hydrogen bonds must be considered to justify the formation of different patterns of hydrogen bonding and, consequently, the formation of less ordered phases. Those characteristics are congruent also with the results obtained from SAXS-WAXS experiments which suggest a more bent configuration for cis-1 than for trans-1.
Departament de Química, Universitat Autònoma de Barcelona , 08193 Cerdanyola del Vallès, Barcelona, Spain.
Alessandro
A
Sorrenti
Departament de Química, Universitat Autònoma de Barcelona , 08193 Cerdanyola del Vallès, Barcelona, Spain.
Ona
O
Illa
Departament de Química, Universitat Autònoma de Barcelona , 08193 Cerdanyola del Vallès, Barcelona, Spain.
Rosa M
RM
Ortuño
Departament de Tecnologia Química i de Tensioactius, Institut de Química Avançada de Catalunya, IQAC-CSIC , c/Jordi Girona 18-26, 08034 Barcelona, Spain.
Ramon
R
Pons
D000596:Amino Acids / Q000737:chemistry*; D003503:Cyclobutanes / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D013501:Surface-Active Agents / Q000737:chemistry*
D000596:Amino Acids; D003503:Cyclobutanes; D013501:Surface-Active Agents