How to Design Non-Kekulč Polyhex Graphs?
نویسندگان
چکیده
Among the vast number of polyhex graphs corresponding to polycyclic aromatic hydrocarbons several graphs are known to have a vexing property with respect to the perfect matching, or Kekulć structure counting problem." Examples are 12 and 23, which have the same number of starred I_I and unstarred IO I atoms but have no Kekule structure (See the left half of Figure 1). Further, both of them have the same number of »upward« and »downward« triangles for their dualist graphs, violating the rule proposed by Balaban for discriminating between closed and open shell systems.š
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