Among the PPAB chromophores, PPAB-2 show higher percentage of CT character which results in higher βtot values, owing to the Thienyl group which is a typical electron-rich substituent. Therefore, the introduction of thienyl as bridge between the A-D is beneficial to enhance the ICT which provides a large transition dipole moment, which can strongly affect the polarizability of the molecule. The tendency to engage in ICT from TPA or DPA to PPAB and moieties, facilitated by suitable π-linkers, is a significant factor in understanding the structure-function relation for designing of NLO materials. It is known that a strong electron 'push-pull' effect has a positive influence on the NLO performance of molecules, and a high electron-donating capacity in a molecule with D-π-A architecture benefits the ICT. Consequently, the electron donating group of PPAB-2 has a greater capacity to donate electrons compared to PPAB-1. This results in a higher ICT (intramolecular charge transfer)