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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
Published on: February 15, 2016
Conformational pseudopolymorphism and orientational disorder in two-dimensional alkyl carbamate crystals
Kibum Kim1, Katherine E Plass, Adam J Matzger
1Department of Chemistry and the Macromolecular Science and Engineering Program, The University of Michigan, 930 North University, Ann Arbor, Michigan 48109-1055, USA.
Abstract:
The structures of self-assembled physisorbed monolayers of alkyl carbamates were examined with atomic detail by scanning tunneling microscopy at the liquid-solid interface. Through systematic variation of molecular structure, the factors determining the two-dimensional crystal packing and dynamics of alkyl carbamate monolayers were isolated. Two different conformational pseudopolymorphs on the surface were observed and their order of stability was varied by changing the length of the alkyl groups. The relative size of the two alkyl groups in a molecule affected the frequency of orientational flipping within a column, which in turn, exerts an influence on the relative orientation of the two-dimensional crystalline domains. These phenomena were explained on the basis of the preferred hydrogen-bonding geometry of the carbamate functional group and the different degree of van der Waals interaction for each form.
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