Synthesis of Diaminopyrimidine Sulfonate Derivatives and Exploration of Their Structural and Quantum Chemical Insights via SC-XRD and the DFT Approach.

Two heterocyclic compounds named 2,6-diaminopyrimidin-4-ylnaphthalene-2-sulfonate () and 2,6-diaminopyrimidin-4-yl4-methylbenzene sulfonate () were synthesized. The structures of heterocyclic molecules were established by the X-ray crystallographic technique, which showed several noncovalent interactions as N···H···N, N···H···O, and C-H···O bonding and parallel offset stacking interaction. Hydrogen-bonding interactions were further explored by the Hirshfeld surface (HS) analysis. Nonlinear optical (NLO) and natural bond orbital (NBO) properties were calculated utilizing the B3LYP/6-311G(d,p) level. Frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) were calculated utilizing the time-dependent density functional theory (TD-DFT) at the same level. The NBO analysis showed that the molecular stabilities of compounds and were attributed to their large stabilization energy values. The second hyperpolarizability (γ) values for and were obtained as 3.7 × 10 and 2.7 × 10 au, respectively. The experimental X-ray crystallographic and theoretical structural parameters of and were found to be in close correspondence. Both the molecules reveal substantial NLO responses that can be significant for their utilization in advanced applications.