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Polymorphism in porphyrin monolayers: the relation between adsorption configuration and molecular conformation
Michiel J J Coenen1, Duncan den Boer, Fieke J van den Bruele
1Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands.
Physical Chemistry Chemical Physics : PCCP
|April 27, 2013
Summary
Self-assembled monolayers of porphyrin copper(II) on graphite exhibit four distinct polymorphs. These structures seamlessly connect due to adaptable molecular conformations, influenced by flexible alkyl tails.
Area of Science:
- Surface Science
- Materials Chemistry
- Nanotechnology
Background:
- Self-assembled monolayers (SAMs) are crucial in surface modification and nanotechnology.
- Understanding the structural diversity and interfacial behavior of porphyrin-based SAMs is key for advanced applications.
Purpose of the Study:
- To investigate the structural characteristics of meso-5,10,15,20-tetrakis(undecyl)porphyrin copper(II) SAMs on a graphite/1-octanoic acid interface.
- To elucidate the factors governing the arrangement and interconnections of different molecular polymorphs.
Main Methods:
- Utilizing Scanning Tunnelling Microscopy (STM) to image and analyze the molecular arrangement.
- Characterizing the unit cell dimensions and polymorphs of the self-assembled monolayers.
Main Results:
- Observation of four distinct polymorphs with varying unit cell sizes.
- Seamless connection between different polymorph arrays via shared unit cell vectors.
- Monolayers are coincident but not commensurate with the graphite substrate.
Conclusions:
- The seamless transitions between polymorphs are attributed to adaptive molecular conformations.
- Conformational freedom of the alkyl tails plays a critical role in enabling these transitions and interfacial adaptation.
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