Multicomponent synthesis of pyrido[2,3-b]pyrazine derivatives: electrochemical DNA sensing, nonlinear optical properties and biological activity

We synthesized novel pyrido[2,3-b]pyrazin based heterocyclic compounds (4–7) and their chemical structures were ascertained by spectral techniques (NMR, FT-IR). Besides experimental investigation, density functional theory (DFT) computations with B3LYP/6-31G(d,p) level of theory were executed to obtain spectroscopic and electronic properties. Nonlinear optical (NLO) properties, frontier molecular orbitals (FMOs), UV-visible, vibrational analysis, natural bond orbitals (NBOs), transition density matrix (TDM) and density of states (DOS) analyses of molecules (4–7) were accomplished at B3LYP/6-31G (d,p) level. Global reactivity parameters (GRPs) were correlated with the band gap (E(gap)) values; compound 7 with lower E(gap) (3.444 eV), exhibited smaller value of hardness (1.722 eV) with greater softness value (0.290 eV(−1)). The dipole moment (μ), average polarizability 〈α〉, first (β(tot)) and second 〈γ〉 hyper-polarizabilities were calculated for compounds (4–7). Compound 7 showed less E(gap), highest absorption wavelength and remarkable NLO response. The highest 〈α〉, β(tot) and 〈γ〉 values for compound 7 were observed as 3.90 × 10(−23), 15.6 × 10(−30) and 6.63 × 10(−35) esu, respectively. High NLO response revealed that pyrido[2,3-b]pyrazin based heterocyclic compounds had very remarkable contributions towards NLO technological applications. Further compounds (4–7) are utilized for the first time in electrochemical sensing of DNA, in vitro antioxidant and antiurease activity.