Highly Efficient Donor-Acceptor Configurated Nicotinaldehyde-based Small Molecules for NLO Materials: Base-Free Deformylation and DFT Study

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, 1H-NMR and 13C-NMR 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 (Egap) 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 (λmax) 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 (λmax =303.496 nm) as compared to other derivatives. Owing to these unique properties, BTMP was also found with significant linear polarizability ⟨α⟩ and hyperpolarizability (βtot and γtot) 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.