Two-dimensional Porphyrin-Fullerene Networks

The unique electrochemical and photophysical properties of porphyrin and [60]fullerene (C60) compounds make them promising candidates for the construction of two- and three-dimensional organic-based materials. Metallo-porphyrins and their derivatives have been shown to be exceedingly useful building blocks for the construction of 3D supramolecular functional networks due to their excellent thermal and chemical stability and synthetic versatility. Materials built from porhyrins could be interesting for various potential applications such as catalysts, molecular sieves, or chemical sensors.
Our work has resulted in close packed monolayers of porhyrins [1] (Figure 1) as well as an unprecedented two-dimensional porphyrin network featuring dynamic pores capable of hosting fullerenes [2] (Figure 2). In this particular system, surface- and porphyrin-driven long-range interactions between the C60 guest molecules and porphyrin layer resulted in the formation of exceptionally large supramolecular hybrid chains and islands.


[1] Davide Bonifazi, Hannes Spillmann, Andreas Kiebele, Michael de Wild, Paul Seiler, Fuyong Cheng, Hans-Joachim Güntherodt, Thomas Jung, François Diederich "Supramolecular Patterned Surfaces Driven by Cooperative Assembly of C60 and Porphyrins on Metal Substrates", Angewandte Chemie 116, Issue 36, 4863 - 4867
[2] H. Spillmann, A. Kiebele, M. Stöhr, T. A. Jung, D. Bonifazi, F. Cheng, F. Diederich "A Two-Dimensional Porphyrin-Based Porous Network Featuring Communicating Cavities for the Templated Complexation of Fullerenes", Advanced Materials 18, Issue 3 ,275 - 279 (2006)

 

Figure 1
Figure 1. STM image of porphyrin–C60 assembly (scan range: 30x30 nm2, It=16 pA, Vbias=2.67 V); the blue circle indicates a C60 vacancy.
Figure 2
Figure 2. a),c),d) Three sequential STM images (scan range: 30 × 30 nm2, Vbias = 2.9 V, It = 12 pA, T = 298 K; the time difference between each image is 62 s). b) Proposed molecular model of a C60 molecule hosted inside a supramolecular porphyrin-based pore. Driven by thermal fluctuations, single C60 ad-molecules (solid circle) are able to displace to neighboring pores as time proceeds. At the same time, bright–dim fluctuations (colored arrows) of single porphyrin molecules propagate through the porous network indicating conformational motion of the 3,5-di(tert-butyl)phenyl moieties. Self-repairing of a defect in the porous structure (dashed ellipse in image a) is also observed.
Figure 3
Figure 3: A chiral nanoporous porphyrin network as host for second layer porphyrin guests. The guests can be found in three distinguishable positions (only two shown). At temperatures above 110 K they switch randomly between these positions. At lower temperatures, the switching can be induced with an STM tip. As the guests do not hop between pores, this is an example of intraporous hopping.