Theoretical investigations of the electronic structure, spectroscopic (IR, Raman and UV–Vis), optoelectronic, thermodynamic and nonlinear optical properties of chromophores of 2-styrylquinoline and 2-(3-nitrostyryl)quinoline.

Computational studies based on Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) were used to determine molecular and thermodynamic parameters, optoelectronic and electronic properties, as well as chemical descriptors, UV–vis spectra and nonlinear optical response of the chromophores of 2-Styrylquinoline (M01) and 2-(3-nitrostyryl)quinoline (M02). We evaluated the impact of the substitution of the hydrogen atom in M01 by the nitro group (NO2) to obtain the molecule M02. The results show very good optoelectronic properties with respect to very high electric fields of the order of 1.43 × 109 Vm−1 for M01 up to 5.26 × 109 Vm−1 for M02. The energy gap decreases from 3.94 eV for M01 to 3.56 eV for M02; which suggest that they are semiconductors. In addition, these two molecules exhibit ionization potential (IP) and electron affinity (EA) quite close to those of Alq3 and could therefore be good candidates for the manufacture of Organic Light-Emitting Diodes (OLED). The chemical descriptors were assessed and allowed us to discuss the stability and reactivity of our molecules. Thus, the addition of the nitro group to the virgin 2-Styrylquinoline decreases the reactivity and stability of the 2-Styrylquinoline. The analysis of the IR and Raman vibrational spectra shows several peaks between 100 cm−1 and 3200 cm−1 of which the most intense for the molecule M01 are attributed to the stretching mode of the C–H bond in the phenyl ring and the C=C double bond in the quinoline ring. For the M02 molecule, stronger peaks were assigned to the stretching mode of the O–N and N–C bonds. The analysis of the UV–vis spectra showed that the maximum absorption wavelength of M01 is 334.80 nm and that of M02 is 375.37 nm; both located in the ultraviolet. The high values of first ( β T ) and second ( γ ¯ ) hyperpolarizability showed that both molecules have very good nonlinear optical properties and thus can be used for second and third harmonic generation. [ABSTRACT FROM AUTHOR]