Poly(1,3-thienyl-squaraine) has been studied by means of semi-empirical and ab initio quantum theories. It has been found to have a very large electron affinity (>9 eV) and thus, would be unstable in the environment. The band gap of the polymer was found to be as low as 0.3-0.6 eV. A distinct transition from a zwitterionic to a quinoidal structure was observed in the progression of increasingly longer oligomers.
Duan, X., Dudis, D. S., & Yeates, A. T. (2001). Electronic structure and energy band gap studies for poly(1,3-thienyl-squaraine) and its dianion. Synthetic Metals, 116(1–3), 285–288. https://doi.org/10.1016/S0379-6779(00)00468-9