Results from different decouplings of the electron propagator theory using MP2/6-311$g$ ($2df$, $2p$) and MP2/6-311$++g$ ($2df$, $2p$) optimized geometries have been performed to investigate first eight vertical ionization energies and the corresponding Dyson orbitals. The results computed are in good agreement with experimental ionization energies and help clear the ambiguities of experimental photoelectron spectrum (PES) assignments. Detailed examination of the 𝜋-orbital density distribution of Dyson orbitals provides clarity in PES assignments and new insights about the topology of ring 𝜋 and ethynyl $\pi_{c-c}$ electron density distribution which may be tapped for improved nonlinear optical/electrochemical response from the thiophenic conjugated polymers.
