Unraveling the NLO potential of isoquinoline functionalized chromophores via molecular modeling using DFT/TD-DFT approaches.

The main focused of this work is the designing of isoquinoline-based derivatives through structural modeling of synthesized compound (BPDI). Two distinct series of derivatives were developed: MPBID1-MPBID6, in which electron-withdrawing groups were introduced at unfused phenyl ring on isoquinoline core and MPBID1'-MPBID6', where substitutions were made at unfused phenyl ring on isoquinoline core. Quantum chemical calculations were employed by DFT/TD-DFT at M06/6-311G(d, p) functional. Frontier molecular orbitals (FMOs), natural bonding orbital (NBO), non-linear optics (NLO), density of states (DOS), global reactivity parameters (GRPs), transition density matrix (TDM) and UV-Visible analyses of designed compounds were performed to understand their NLO responses. FMO results are supported by TDM analysis showing that all the designed compounds have smaller energy gap values than the reference compound. Among all the designed compounds, MPBID4' is the most suitable candidate for NLO study because of the lowest energy gap with a larger bathochromic redshift. NBO study has confirmed the stability of compounds. Dipole moment, average hyperpolarizability, first hyperpolarizability and second hyperpolarizability values of designed compounds were also better than that of reference compound. This study reveals that structural tailoring performs a key role in the development of attractive and best NLO materials for optoelectronic devices.