Abstract
The synthesis of 5-azaazulenes with both donor and acceptor substituents on their seven-membered rings is reported through the ring expansion of stable azapentalene derivatives upon reaction with dimethyl acetylenedicarboxylate. Regioisomeric products were obtained and characterized. The mechanism of the transformation and the excited state energy levels of the products were studied computationally, suggesting that these structures can be entry points to chromophore design for organic photonics applications.