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IR and UV-VIS spectroscopic characterization of norbadione A and study of the electronic properties of other pigments derived from pulvinic acid

2023; Elsevier BV; Volume: 1285; Linguagem: Inglês

10.1016/j.molstruc.2023.135491

1872-8014

Ana G.N. Camara, Francisco Wagner Queiroz Almeida-Neto, Yana L.C. Silva, Fátima Miranda Nunes, Marcos Carlos de Mattos, Jair Mafezoli, Francisco Geraldo Barbosa, Emmanuel Silva Marinho, Pedro de Lima‐Neto, Maria da Conceição Ferreira de Oliveira,

Free Radicals and Antioxidants

Pulvinic acid-derivative pigments are characterized by the presence of one or more units of pulvinic acid (1) in their molecular structures. Due to their highly conjugated structures, this class of pigments presents significant photochemical properties, including the absorption of UV radiation with high coefficient absorption bands. Here, the spectroscopic characterization of norbadione A (2), a naphtalenoid pulvinic acid derivative isolated from the fungus Pisolithus tinctorius, was made by comparison of its IR and UV-VIS data obtained from experimental and theoretical procedures. Linear correlation between the experimental and theoretical wavenumbers obtained in the IR spectroscopic analyses presented a coefficient of determination (R²) of 0.99576 with a linear equation y = 0.9729x +37.26261, confirming the proposed chemical structure of norbadione A (2). All fundamental vibrational modes were assigned using theoretical quantum calculations. The experimental UV-VIS spectrum of 2 presented bands at 270, 371, and 419 nm, and quantum chemical calculations enabled the assignment of the electronic transitions in each band. Additionally, the electronic properties of pulvinic acid (1) and its derivatives norbadione A (2), badione A (3), bisnorbadioquinone A (4), and pisoquinone (5) were investigated. For all compounds, the Frontier Molecular Orbitals and Fukui functions were calculated at a B3LYP/6-311++G(d,p) computational level in the gas phase. Distinct regions of HOMO and LUMO molecular orbitals were observed, which means that the molecules may have different reactivity; also that the reactivity of the derivative compounds is greater than the precursor acid 1.