Research Topics:
Molecular Electronics
Integration of molecular structures as active components in electronic circuits is a visionary concept and a scientific challenge at the same time.[1] The predicted attainable feature sizes together with the potential cost to performance relationship are the main driving forces of this molecular approach to electronic functions. However, the field is still in its infancy and the investigation and comprehension of the relationship between molecular structure and electronic transport properties are the most important tasks for further developments. Studies of molecules in electronic circuits are strongly interdisciplinary with synthetic chemistry and experimental physics as key players. The chemistry job is the design and the synthesis of tailored molecular structures for both, the envisaged experiment and also particular electronic functions. Synthetic chemistry enabled for example the design and the synthesis of two rigid-rod type molecules 1 and 2. Both rods differ mainly in their spatial symmetry along the molecules axis. The symmetry of the designed molecular rods was reflected in the current investigations. As for a randomized assembly of several asymmetric rods the symmetry information would be averaged out, we were able to demonstrate that indeed single molecules are investigated.[2]
Figure 1: Typical I/V characteristics through the symmetric rod 1 and the asymmetric rod 2, recorded at RT in a mechanically controlled break junction.[2]
he investigations of the correlations between molecular structures and electronic transport properties of single molecules has been expanded to more insulating metalorganic platinum complexes[3] and to rods which differ in the relative positions of their anchor groups, [4] or with reduced p-conjugation. [5] Lately, we synthesized single-molecule rectifiers[6] and currently, we are working on different molecular switches,[7] electrochemically gated systems [8] and memory devices.
[1]: M. Mayor, H. B. Weber Chimi 2002, 56, 494-499; M. Mayor, H. B. Weber, R. Waser, in "Nanoelectronics and Information Technology – Advanced Electronic Materials and Novel Devices" Ed. R. Waser, Wiley-VCH, Weinheim (2003) 501-526.
[2]: J. Reichert, R. Ochs, D. Beckmann, H. B. Weber, M. Mayor, H. v. Löhneysen Phys. Rev. Lett.2002, 88, 176804/1-176804/4.
[3]: M. Mayor, C. v. Hänisch, H. B. Weber, J. Reichert, D. Beckmann Angew. Chem. Int. Ed. 2002, 41, 1183-1186.
[4]: M. Mayor, H. B. Weber, J. Reichert, M. Elbing, C. von Hänisch, D. Beckmann, M. Fischer Angew. Chem. Int. Ed. 2003, 42, 5834-5838.
[5]: E. Lörtscher, M. Elbing, M. Tschudy, C. von Hänisch, H. B. Weber, M. Mayor, H. Riel ChemPhysChem. 2008, 9, 2252-2258
[6]: M. Elbing, R. Ochs, M. Koentopp, M. Fischer, C. von Hänisch, F. Weigend, F. Evers, H. B. Weber, M. Mayor PNAS 2005, 102, 8815-8820.
[7]: J. M. Mativetsky, G. Pace, M. Elbing, M. A. Rampi, M. Mayor, P. Samorì J. Am. Chem. Soc. 2008, 130, 9192-9193.
V. Ferri, M. Elbing, G. Pace, M. D. Dickey, M. Zharnikov, P. Samorì, M. Mayor, M. A. Rampi Angew. Chem. Int. Ed. 2008, 47, 3407-3409
[8]: N. Weibel, A. Blaszczyk, C. von Hänisch, M. Mayor, I. Pobelov, T. Wandlowski, F. Chen, N. Tao Eur. J. Org. Chem. 2008, 1, 136-149
Nano-Objects and –Architectures
Nanoscale objects display particular interesting physical properties due to their size restrictions for electronic waves. Quantization effects are ruling their physics giving new challenges and opportunities for both, fundamental research and potential applications. Therefore, the control over size, shape and material properties of nanoscale objects is crucial to design and tailor their physical properties. Nowadays two different strategies are pursued to fabricate nanoscale objects. While improved lithographical and other physical methods allow to reduce the manufactured objects size (top-down approach), advanced synthetic chemistry and supramolecular approaches constantly increase the size of available molecules and super-molecules ("bottom-up approach"). Synthetic chemistry can be understood as engineering at the nanoscale and allows to assemble nanoobjects with very particular physical properties. An example is the recent synthesis of a molecular ring with a diameter of 12 nm and a periphery consisting exclusively of conjugation-active building blocks.[9]
Figure 2: The front page of Angewandte displays the ring molecule with a 12 nm diameter and the front wheel of the bicycle "Eleanor" inspiring the 16 fold symmetry.
This ring object was designed with regard to its electronic transport - and supramolecular packing properties and will hopefully allow first investigations of persistent currents in organic molecules.
Current activities are geared towards well defined three dimensional objects like tubular systems assembled from molecular rings or ball shaped heteroatom rich macromolecules both designed to display promising electronic and optical properties. Another endeavor is towards functionalization and patterning of surfaces by self assembly.[10]
[10]: Z. Mu, L. Shu, H. Fuchs, M. Mayor, L. Chi J. Am. Chem. Soc. 2008, 130, 10840-10841. L. Shu, M. Mayor Chem. Comm. 2006, 4134-4136. L. Shu, Z. Mu, H. Fuchs, L. Chi, M. Mayor Chem. Comm. 2006, 1862-1863. L. Shu, M. Müri, R. Krupke, M. Mayor Org. Biomol. Chem. 2009, 7, 1081-1091.
