3,7,8-Trihydroxy-3-methyl-10-oxo-4,10-dihydro-1H,3H-pyrano [4,3-b]chromene-9-carboxylic acid is a structurally well-characterized fulvic acid (FA) capable to act as a polyfunctional bidentate ligand in the complexes with metal ions. Investigations of the formation mechanisms and structure of the above-mentioned FA complexes with bivalent metals [Cd(II), Cu(II), Mg(II), Ni(II), Pb(II) and Zn(II)] are presently an actual and trending topic in the modern chemistry of humic and fulvic acids. Furthermore, the importance of the theoretical DFT investigations of binding of metals with fulvic acids is stipulated by the lack of the relevant experimental structural data for such complexes.

The quantum chemical calculations have shown that, of the four possible FA tautomers, the two FA forms are more stable. The wavefunction analysis and computed reactivity descriptors (electrostatic potential, Hirshfeld surface analysis, natural population analysis charges, and condensed Fukui indexes) give the insight on the properties and reactive ability of these two different forms of the FA. The computed thermochemical parameters of the ion-exchange reaction explain the metal binding affinity and selectivity of the FA forms.

3,7,8-三羟基-3-甲基-10-氧代-4,10-二氢-1H，3H-吡喃[4,3 - b ]色烯-9-羧酸是一种结构良好的富勒酸（FA ）能够在与金属离子的复合物中充当多官能双齿配体。目前正在研究上述具有二价金属的FA配合物的形成机理和结构[Cd（II），Cu（II），Mg（II），Ni（II），Pb（II）和Zn（II）]。腐殖酸和黄腐酸的现代化学中一个现实的趋势，并且是趋势。此外，缺乏这类配合物的相关实验结构数据表明了理论上DFT研究金属与黄腐酸结合的重要性。

量子化学计算表明，在四种可能的FA互变异构体中，两种FA形式更稳定。通过波函数分析和计算出的反应性描述符（静电势，Hirshfeld表面分析，自然种群分析电荷和凝聚的Fukui指数），可以洞悉这两种不同形式的FA的性质和反应能力。计算的离子交换反应的热化学参数解释了FA形式的金属结合亲和力和选择性。