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 Suzukicross -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 ( 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 ( lambda 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 ( lambda max =303.496 nm ) as compared to other derivatives. Owing to these unique properties, BTMP was also found with significant linear polarizability < alpha > and hyperpolarizability ( beta tot and gamma tot ) values i.e., 2.816x10 - 23 , 1.855 x 10 -30 and 4.553 x 10 -35 esu. , respectively among the titled compounds. These findings indicated the potential use of these organic derivatives in the NLO applications.