Multicomponent synthesis of pyrido[2,3-b]pyrazine derivatives: electrochemical DNA sensing, nonlinear optical...

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.