Synthesis and structural characterization and DFT calculations of the organic salt crystal obtaining 9-aminoacridine and picric acid: 9-Aminoacridinium picrate

Abstract

Organic salt, 9-aminoacridinium picrate (9-AAcPc), containing equimolar quantities of 9-aminoacridine and picric acid was obtained and a single crystal was grown by the slow evaporation method in the mixture of methanol: tetrahydrofuran solvent (1: 1, v: v). The molecular structure of the prepared compound was confirmed by FT-IR, ¹H NMR, and ¹³C NMR spectroscopic methods, as well as single crystal X-ray diffraction analysis. The X-ray diffraction analysis of the crystal structure of the title compound showed the presence of the triclinic space group P-1 with no. 2, a = 8.2811(7) Å, b = 10.1003(9) Å, c = 13.4484(13) Å, α = 83.521(3)°, β = 83.330(3)°, γ = 66.595(3)°, V = 1022.56(16) Å³, Z = 2, μ(MoKα) = 0.108 mm^-1, D_calc = 1.375 g/cm³, 56338 reflections measured (5.89° ≤ 2Θ ≤ 56.704°), 5097 unique (R_int = 0.0400, R_sigma = 0.0210) which were used in all calculations. The final R₁ was 0.0552 (I > 2σ(I)) and wR₂ was 0.1757 (all data). The molecular geometry was also optimized using density functional theory. The frontier molecular orbitals were calculated, and we discussed the probability that the proton transfers from the phenolic OH group of picric acid to different nitrogen units. The calculated electronic structure properties of the title molecule, such as the HOMO and LUMO analysis, and different molecular electrostatic potential maps, were obtained by using the density functional theory method, and the calculated structure was compared with the experimental structure. The thermal stability of the crystal was also analyzed using the TGA/DTG technique.