Isospectral Single Coronoids

Chart 2.4. A pair of isospectral single coronoids and their 78 roots of the characteristic polynomial (x values). 

Kekulean. These two Ci gH Q systems have 24 hexagons each and are reproduced in Chart 4. The 78 roots of the corresponding characteristic polynomials were computed, and it was verified that they indeed are identical the numerical values are included in Chart 4. 

It was also confirmed that the Kekule structure count is the same for the two isospectral systems under consideration K = 12636. It is interesting that the pair of systems consists of one half essentially disconnected (HED) and one essentially disconnected single coronoid. The two schemes of Kekule structures for the HED system (left-hand drawing in Chart 4) are indicated below. 

Here the Kekule structure counts are = 02x78 = 6318 and = 0x702 = 6318 when referring to the above diagram. In total, K = = 12636. The essentially disconnected system at the 

Is the pair of single coronoids in Chart 4 the smallest pair of isospectral coronoids  

---