Highly efficient donor-acceptor configurated Nicotinaldehyde-based small molecules for NLO materials: Base-free deformylation and DFT study.

• Synthesis of donor-acceptor configurated nicotinaldehyde for NLO materials. • Structure confirmation through various spectroscopic technique. • Study of key electronic properties at M06/6–311 G (d,p) functional. • Utilization of TD-DFT approach for FMOs and UV–Vis analyses. In the current study, 6-methyl nicotinaldehyde derivatives (MNP - BTMP) were synthesized by using the Suzuki- cross-coupling method which involved deformylation approach. The FTIR, UV–Visible, 1HNMR and 13CNMR spectroscopic analyses were performed to validate the structures of newly synthesized derivatives. Additionally, the density functional theory (DFT) approach at M06/6–311G(d,p) level was utilized in order to calculate their optoelectronic and nonlinear optical (NLO) properties. Consequently, their HOMO-LUMO band gaps (E gap) were obtained in the range of 4.77–5.55 eV. A significant charge transfer from HOMO towards LUMO was investigated which was further supported by DOS. Moreover, they exhibited the maximum absorption wavelengths (λ max) in the UV- Vis region as 269.989–303.496 nm. Among the derivatives, BTMP was found with the least energy gap (4.77 eV) and the red-shifted absorption spectra (λ max =303.496 nm) as compared to other derivatives. Owing to these unique properties, BTMP was also found with significant linear polarizability ⟨ α ⟩ and hyperpolarizability (β tot and γ tot) values i.e., 2.816×10−23, 1.855 × 10−30 and 4.553 × 10−35 esu. , respectively among the titled compounds. These findings indicated the potential use of these organic derivatives in the NLO applications. [ABSTRACT FROM AUTHOR]