What’s in the box?
26 March 2010
It is a long-held ambition of scientists to prepare porous solids within which they are able to mimic the sophisticated chemistry performed by Nature. A paper published in the journal Science describes research by Dr. Grazia Bezzu and Prof. Neil McKeown in which beautiful nanoporous crystals are made from iron phthalocyanine, a close relative of the important biologically active unit heme. These crystals contain very large (8 nm3) interconnected voids that allow access to the reactive iron centres.
The nanoporous crystals are unusual in that they are made of discrete molecules rather than an extended framework such as the much-studied Metal-Organic-Frameworks (MOFs). Usually such nanoporous molecular crystals are very unstable but by taking inspiration from the use of cavity wall-ties in architectural engineering, the iron phthalocyanine crystals could be stabilised by the addition of suitable bidentate ligands, which bind between two iron centres to act as ‘molecular wall-ties’.
The coordination chemistry within the crystal was observed directly by x-ray crystallography in collaboration with Dr. Madeleine Helliwell (University of Manchester) using the synchrotron radiation source at Diamond (Station I19). The Engineering and Physical Sciences Research Council (EPSRC) fund the research.
Figure 1: The crystal structure of the nanoporous crystal showing the “molecular wall-tie” ligands (green) binding between the iron centres.