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

[Image: see text] Two heterocyclic compounds named 2,6-diaminopyrimidin-4-ylnaphthalene-2-sulfonate (A) and 2,6-diaminopyrimidin-4-yl4-methylbenzene sulfonate (B) 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 A and B were attributed to their large stabilization energy values. The second hyperpolarizability (γ(tot)) values for A and B were obtained as 3.7 × 10(4) and 2.7 × 10(4) au, respectively. The experimental X-ray crystallographic and theoretical structural parameters of A and B were found to be in close correspondence. Both the molecules reveal substantial NLO responses that can be significant for their utilization in advanced applications.