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Not every study leads to structural designs. Sometimes it is necessary to correct, or at least question, notions that were created by experimental or computational errors. A clear case of this is in the classic report of extremely long bonds in molecules like 9,10-dimethyleneanthracene dimer photoisomer or lepidopterene . Ab initio calculations that we performed in this area did not agree with the original experiment and when we rechecked the X-ray structure of the former compound, we found the original structure was in error. This now opens up questions concerning the mechanisms through which orbital interactions lead to bond lengthening, questions we are now investigating.
The size of these chemical structures and the need for high accuracy makes the computational effort of these projects extremely intensive. Some of our most exciting problems require extensive basis sets and/or dynamic correlation, utilizing density functional methods on systems of greater than 50 atoms, all of which makes machine size a severe limitation. Our team is certainly not platform limited, accessing the C90, Paragon, T3D, SP2 and alpha-farm cluster, to be able to maintain our usual assault on stereochmeical problems. We benefit from the work we put into making our packages portable to almost any platform.
The importance of the kinds of research done in our efforts can be found if one realizes that aromatic subunits are found in a large number of everyday materials. Petrochemicals from aircraft fuel to common charcoal, depend on aromatic chemistry. The agrochemical and pharmaceutical industry produces vast varieties of aromatic and heteroaromatic molecules as the bases to their most active drugs and agricultural aids. Modern textiles and dyes would be unthinkable without aromatics. On the negative side, aromatic residues have a heavy environmental impact as well. Clearly, progress in amplifying the benefits and reducing the drawbacks will come from understanding and design.