Computational insights into Alizarin for toy applications using DFT calculations of photophysical properties and spectroscopic safety

Alizarin (1,2-Dihydroxyanthracene-9,10-Dione), a natural anthraquinone dye, was investigated via DFT and TD-DFT at the B3LYP/def2-SVP level for potential toy applications. The optimized structure confirmed that a planar π-conjugated system is essential for dye properties. Electronic structure calculations revealed a HOMO‒LUMO gap of 1.79 eV, with the highest intensity absorption at 483.8 nm (f = 0.130), corresponding to orange‒red coloration (CIE: 0.62, 0.35). The Mulliken charge distribution revealed significant polarization at the oxygen atoms (− 0.16 to − 0.17e) and hydroxyl hydrogens (+ 0.17 to + 0.18e). The calculated ¹³C NMR shifts for carbonyl carbons at 212.8 and 213.2 ppm and aromatic carbons at 123.2–165.5 ppm, along with the ¹H NMR shifts at 7.4 ppm (aromatic) and 5.2–5.6 ppm (phenolic hydroxyl), provide definitive structural identification. The safety profile demonstrated nontoxicity, with LD₅₀ > 5000 mg/kg, no mutagenic effects, no skin sensitization, and regulatory approval by the FDA/EU, suggesting that Alizarin is a promising green alternative for sustainable toy manufacturing.