Metallosupramolecular Chemistry in Two Dimensions

Abstract

Ultrathin films of metallosupramolecular coordination polyelectrolytes (MEPEs) on planar solid substrates assembled by electrostatic layer-by-layer self-assembly (ELSA) are characterized with UV-vis spectroscopy, optical ellipsometry, and X-ray reflectometry. MEPEs based on different ditopic ligands and transition metal ions are employed and shown to form regular ELSA multilayers. A quantitative analysis is in agreement with a surface coverage of approximately two MEPE monolayers per deposition step. In addition, we demonstrate that multilayers of MEPEs with different transition metal ions can be assembled. Even with kinetically labile metal ions, there is no metal ion exchange in these multilayers. Absorption spectra of multilayers on silicon show a band inversion of the MLCT band, which is rationalized in terms of optical effects.

Keywords:

• Electrostatic layer-by-layer self-assembly
• Thin films
• Supramolecular chemistry
• Metallosupramolecular coordination polyelectrolytes
• Materials

Acknowledgements

The authors thank Helmuth Möhwald for valuable discussions. Financial support by Deutsche Forschungsgemeinschaft (DFG) is greatly appreciated.

Notes

The Future of Supramolecular ChemistryIntelligent and dynamic systems are one of the next frontiers in supramolecular chemistry. For the realization of such materials, it will be necessary to improve existing methods and to innovate new routes to organize supramolecular modules in structurally coherent macroscopic architectures. In analogy to biological systems, semi-ordered mesoscopic materials will become increasingly important. Applying principles of self-organization in device fabrication provides opportunities that go far beyond currently existing technologies and will have a profound impact on the technological development far into the 21st century. However, further progress in this area will rely on an interdisciplinary approach. In this sense, the visionary claims of a supramolecular paradigm may provide an incentive to combine forces towards interdisciplinary research programs that go beyond “classical” approaches in chemistry, engineering, or physics.D. G. Kurth studied chemistry at the University of Cologne, the Technical University of Aachen, the University of New Mexico, and Purdue University. After he finished his PhD in the group of T. Bein, he went as post-doc to Strasbourg to work with J.-M. Lehn. Since 1996, he has been an independent project leader in the Department of Interfaces headed by H. Möhwald at the Max Planck Institute of Colloids and Interfaces at Potsdam.