Journal Article

PUBDB-2021-00208

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Lattice and thermodynamic characteristics of N -stearoyl-allo-threonine monolayers

Brezesinski, G.Extern* ; Rudert, R. ; Vollhardt, D. (Corresponding author)

2020
RSC Publ. Cambridge

This record in other databases:        

Please use a persistent id in citations: doi:10.1039/C9CP06304H  doi:10.3204/PUBDB-2021-00208

Abstract: The effect of the second chiral center of diastereomeric N-alkanoyl-allo-threonine on the main monolayer characteristics has been investigated. The characteristic features of the enantiomeric and racemic forms of N-stearoyl-allo-threonine monolayers are studied on a thermodynamic basis and molecular scale. The $π$–A curves of the enantiomeric and racemic allo-forms show similar features to those of N-stearoyl-threonine. The compression curves are always located above the corresponding decompression curves and the decompression curves can be used as equilibrium isotherms for both the enantiomeric and racemic N-stearoyl-allo-threonine. The absolute T$_0$-values (disappearance of the LE/LC-transition) are 4–5 K larger compared with the corresponding N-stearoyl-threonines, but the $Δ$T$_0$ between the enantiomeric (D) and the racemic (DL) forms is only slightly larger than that of N-stearoyl-threonine. The difference in the critical temperatures T$_c$, above which the monolayer cannot be compressed into the condensed state, between the enantiomeric and the racemic forms, is quite small ($Δ$T$_c$ = 0.8 K) and is smaller compared to that of the corresponding threonines ($Δ$T$_c$ = 1.8 K). This is consistent with the dominance of the van der Waals interactions between the alkyl chains reducing the influence of chirality on the thermodynamic parameters. GIXD studies of N-stearoyl-allo-threonine monolayers provide information about the lattice structure of condensed monolayer phases on the Angstrom scale and stipulate the homochiral or heterochiral preference in the condensed phases. Comparable to N-stearoyl-threonine, the enantiomers exhibit an oblique lattice structure, whereas the racemates form a NNN tilted orthorhombic structure demonstrating the dominance of heterochiral interactions in the racemates independent of the diasteomeric structure change of the polar head group. The A$_0$ values are characteristic for rotator phases. The smaller A$_0$ value obtained for the racemic monolayers indicates their tighter packing caused by heterochiral interactions. The program Hardpack was used to predict the geometric parameters of possible 2-dimensional packings. For comparison with the experimental GIXD data, the two-dimensional lattice parameters and characteristic features of the enantiomeric and racemic diastereomeric stearoyl-threonine monolayers were calculated and are in reasonable agreement with the experimental GIXD data.

---

Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

Experiment(s):

1. DORIS Beamline BW1 (DORIS III)

Appears in the scientific report 2020

---

Database coverage:
; ; ; Allianz-Lizenz / DFG ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF < 5 ; JCR ; National-Konsortium ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

---